Nanomaterials describe, in principle, materials of which a single unit is sized between 1 to 1000 nanometres but usually is 1 to 100 nm.

What is Silicon Boride Powder?

,Silicon Boride Powder
Silicon Boride (also known as boron silicide) is a lightweight ceramic compound made up of silicon and boron. There are silicon triboride, silicon tetraboride, silicon hexaboride, and so on.
Silicon hexaboride or hexaboron silicide is a glossy black gray powder. The chemical formula is SiB6. The molecular weight is 92.95. The relative density is 2.47 g/cm3, the melting point is 2200℃. The hardness is between diamond and ruby. Silicon hexaboride can conduct electricity. It is insoluble in water. When heated in chlorine and water vapor, the surface can be oxidized.

Physicochemical Properties of Silicon Boride Powder
The SiB6 crystal structure consists of interconnected icosahedrons (polyhedrons with 20 faces), icosahedrons (polyhedrons with 26 faces), and isolated silicon and boron atoms.
It is insoluble in water and resistant to oxidation, thermal shock, and chemical erosion. Especially under thermal shock, it has high strength and stability. The grinding efficiency is higher than boron carbide.
Surface oxidation occurs when SiB6 is heated in air or oxygen and is eroded at high temperatures by boiling sulfuric acid and fluorine, chlorine, and bromine. Borides are electrically conductive. Hexamborides have a low thermal expansion coefficient and high thermal neutron cross-section.

Silicon Boride Powder Properties
Other Names silicon hexaboride, SiB6 powder
CAS No. 12008-29-6
Compound Formula SiB6
Molecular Weight 92.95
Appearance dark grey to black powder
Melting Point 1950℃
Boiling Point N/A
Density 2.43g/cm3
Solubility in H2O insoluble
Exact Mass 93.04

 

Silicon Boride SiB6 Powder CAS 12008-29-6

Preparation Methods of Silicon Boride Powder
The mixture of boron and silicon can be heated directly, the excess silicon can be removed with HF and HNO3, and the B3Si in the mixture can be decomposed with molten KOH.

Applications of Silicon Boride Powder
1 Used as various standard abrasives and grinding cemented carbide;
2 used as engineering ceramic material, sandblasting nozzle, manufacturing gas engine blade, and other special-shaped sintering parts and seals.
3. Used as an oxidant for refractories.

What is Boron Carbide Powder B4C?

About Boron Carbide Powder
Boron carbide powder is hard, black, and shiny. Its hardness is lower than industrial diamond but higher than silicon carbide. Boron carbide is less fragile than most pottery. It has a large thermal neutron capture cross-section, and strong chemical resistance. It is not subject to attack by hot hydrogen fluoride and nitric acid. It is soluble in molten alkali and insoluble in water and acid. The relative density (D204) is 2.508 to 2.512. The melting point is 2350 ℃. The boiling point is 3500 ℃.

Physicochemical Properties of Boron Carbide Powder
Boron carbide does not react with acid and alkali solution and has high chemical potential. It has the properties of neutron absorption, wear-resistance, and semiconductor conductivity. It is one of the most stable substances to acids and is stable in all concentrated or dilute acid or alkaline water solutions. Boron carbide is basically stable under 800℃ in the air environment.
When some transition metals and their carbides coexist, they have special stability. The transition metals ⅳ, ⅴ, and ⅵ in the periodic table react strongly with boron carbide powder to form metal borides at 1000 ~ 1100℃. At higher reaction temperatures, it has been reported that boron carbide tends to nitride or react with transition metal oxides to form corresponding boron nitride and borides, which are mainly rare earth and alkaline earth metal hexaborides.
It has a Mohs hardness of about 9.5 and is the third hardest substance known after diamond and cubic boron nitride, which is harder than silicon carbide.
Due to the preparation method, boron carbide is easy to form carbon defects, resulting in a wide range of boron to carbon ratio changes without affecting the crystal structure, which often leads to the degradation of its physical and chemical properties. Such defects are difficult to be resolved by powder diffraction and often require chemical titration and energy loss spectrum.

Boron Carbide Powder Properties
Other Names B4C, B4C powder, black diamond, boron carbide powder
CAS No. 12069-32-8
Compound Formula B4C
Molecular Weight 55.26
Appearance gray black powder
Melting Point 2763°C
Boiling Point 3500°C
Density 2.52g/cm3
Solubility in H2O insoluble
Exact Mass N/A

 

Boron Carbide B4C Powder Cas 12069-32-8
Applications of Boron Carbide Powder
Boron carbide is suitable for hard materials of drilling, grinding, and polishing, such as hard alloy, ceramic wear parts including wear plate, pump parts, bearings, faucet, nozzle, valve parts engineering ceramics, biological ceramics, nuclear reactor pellet, lightweight body armor materials applications. Specifically,
1. Used to control nuclear fission. Boron carbide can absorb large amounts of neutrons without forming any radioactive isotopes, making it an ideal neutron absorber for nuclear power plants, where neutron absorbers control the rate of nuclear fission.
2. As abrasive materials. Boron carbide has been used as a coarse abrasive material for a long time. Because of its high melting point, it is not easy to cast into artifacts, but by melting at high temperatures, it can be machined into simple shapes. Used for grinding, drilling, and polishing of hard materials such as hard alloy and precious stone.
3. For coating coatings. Boron carbide can also be used as a ceramic coating for warships and helicopters. It is lightweight and has the ability to resist armor-piercing bullets penetrating the hot-pressed coating as a whole.
4. For the nozzle. It is used in the arms industry to make gun nozzles. Boron carbide is extremely hard and wear-resistant, does not react with acid and alkali, has high/low-temperature resistance, high-pressure resistance, density ≥2.46g/cm3;  Microhardness ≥ 3500kGF /mm2, bending strength ≥400MPa, melting point is 2450℃. Because the boron carbide nozzle has the characteristics of wear resistance and high hardness, the boron carbide sandblasting nozzle will gradually replace the known carbide/tungsten steel and silicon carbide, silicon nitride, alumina, zirconia, and other materials of the sandblasting nozzle.
5. Others. Boron carbide is also used in the manufacture of metal borides and smelting of sodium boron, boron alloys, and special welding.

Properties and applications of Aluminum Oxide nanoparticles

In today’s world, nanoparticles are playing a key role in making this world a better place by serving in different fields and industries through various means and sources. Aluminum oxide is a compound comprising aluminum and oxygen where its formula is known and written as Al2O3.

The entire chemical compound has diversity in its nature and possesses remarkable properties and characteristics which enable its production and applicability at a large scale. The prominent and most significantly used applications of aluminum oxide can be seen in the field of biomedical as they are being used in this field for quite a long time and benefiting this area of science immensely.

Introduction

The improved characteristics of nanoparticles are the reason for them being utilized so much in industry and research than the bulk materials. Ultrafine particles of smaller sizes than 100 nm fabricates nanoparticles. The effects are because of its small size as a good amount of atoms are exposed on the surface when they are made from the nanoparticles. When they are made from a nanoscale, significant changes come in the behavior and performance of the materials. When they are composited from nanoparticles, enhancements are made, for instance, enhanced thermal conductivity, enhanced electrical conductivity, and enhanced strength and hardness.

 

Aluminum oxide

Al2O3 is the chemical formula of Aluminum oxide, which is oxygen and aluminum’s chemical compound. Aluminum oxide is known as Aluminum (III) oxide and it occurs the most out of various other aluminum oxides. Commonly, it is known as alumina and can be identified as alundum, aloxite, or aloxide depending on certain applications or forms. Aluminum oxide is important for producing aluminum metal, as a refractory material because of its high melting point and as an abrasive because of its hardness.

Aluminum oxide nanoparticles

Nanosized aluminum oxide, also known as nanosized alumina, comes in the spherical form or the form of closely spherical nanoparticles, and oriented form or undirected fibers. Despite have spherical morphology, aluminum oxide nanoparticles look like white powder. They are graded as an irritant and highly flammable in both solid and liquid forms as they can be the factor in serious respiratory and eye irritation.

Properties of nanoscale colloidal alumina particles

Their fibers and particles are of a small diameter which is 2-10 nm. They have more than 100m2/g specific surface area. High defectiveness of the nanoparticles’ specific structure and material surface. Following are included in the nanoparticle’s specific structure and there is a possibility of modification in them; surface composition, structure, phase composition, degree of crystallinity, and pores’ size and volume.

Properties of the nanoscale fibers of aluminum oxide

20,000,000:1 is their length-diameter ratio. Their fibers are highly oriented. The fibers have a weak interaction among themselves. There are no surface pores in it. They have a high surface concentration of the hydroxyl groups

Physiochemical properties

The dimensions and size of the nanoparticles heavily determine the nanoparticle’s physiochemical characteristics. When the size changes, there comes a difference in the atomic arrangement too in the nanoparticles. According to reports, nanoparticles have 3 distinctive layers and they are not pointed objects. The surface layer is the outermost and first layer. The surface layer is made up of metal ions or molecules and they are the reason for the functioning of the nanoparticle’s surface eventually. The shell layer is the 2nd layer and it is very different from the first and the third layer. The nanoparticle’s core is the last and third layer and it represents the nanoparticle’s basic chemical formula itself.

Structure determination

Thermal, magnetic, mechanical, optical, and electrical characteristics come in the general physicochemical properties. The energy levels and electrons determine the electric conductance, emission, and absorption, making optical and electronic characteristics symbiotic. Emission and spectra of absorbance are displayed by the nanoparticles. Nanoparticles’ capillary force, friction, adhesion, elastic modulus, hardness, and other mechanical characteristics are studied for facilitating these particles’ usage in the industry. When it comes to synthesizing wear resistance products, scientists use improved hardness. Long-lasting lubricants are designed by using low friction, and adhesion is used for the particle removal processes.

Thermal properties

Nanoparticle’s thermal characteristics are determined by the kind of metal that makes up the nanoparticles. In comparison with most non-metallic compounds’ fluids or solids, a higher thermal conductivity is possessed by oxides of aluminum and metals like copper. When nanoparticles are added to these metal oxides and metals, it enables the fluid to have an enhanced thermal conductivity whereas it was a bad thermal conductor before.

Manufacturing process

Laser ablation, hydrothermal, sputtering, pyrolysis, sol-gel, and ball milling are among the many techniques that can be used to synthesize Aluminum oxide nanoparticles. However, the most commonly utilized method for the production of nanoparticles is laser ablation as it can be made in liquid, vacuum, or gas. Laser ablation offers many benefits in comparison with other techniques like high and rapid purity processes.

Moreover, one can easily collect the nanoparticles that are made through the laser ablation of materials in liquids as compared to the nanoparticles that are made through the laser ablation of materials in the gas state. A way was recently found by Max-Planck-Institut für Kohlenforschung, a chemist in Mülheim an der Ruhr for producing corundum (alpha-alumina), alumina’s extremely stable variant, in nanoparticle’s form by utilizing the simple mechanical method in a ball mill.

Derivation of aluminum oxide

Recycled alumina and bauxite mineral are the two main sources of aluminum oxide. However, bauxite mineral, aluminum’s ore is the main significant source of aluminum oxide. Instead of being a mineral, Bauxite mineral is a sedimentary rock, made up of a mixture of aluminum compounds with other nonmetals, metals, and their oxides like quartz (SiO2), magnetite (Fe3O4), and hematite (Fe 2O3). Brazil, Jamaica, China, and Australia are bauxite’s biggest manufacturers. Alumina has one small natural source but due to its frequent characterization as a gem and because of its characteristics of reflection and light absorption in the visible range when it is mixed with transition metals, it leads to a beautiful and colorful crystal.

Recycling of virgin aluminum

One of the other easy methods to obtain aluminum oxide is to recycle virgin aluminum. Due to aluminum oxide’s characteristics of hardness and durability, one can’t see the existence of the dissimilarities in functionality and characteristics of the virgin Aluminum and its recycled counterparts. In recycling, energy is utilized in a very small amount and unrecyclable Aluminum oxide’s amount is 10%, which is very low and it makes this particular source an extremely fascinating one particularly for industries like the construction industry as they utilize aluminum oxide in huge amount. Sufficient aluminum oxide is provided by these 2 sources to the world but better techniques might be used for our planet’s sustainability as mining is included.

Bayer process

When the bauxite mineral is obtained, then the Bayer process is used for crushing it and then purifying it to Aluminum. Just moments after sodium hydroxide’s hot solution is used to wash the bauxite mineral, aluminum is produced, and then aluminum oxide is obtained. The obtained aluminum hydroxide later gets calcinated to alumina. Rarely corundum or obtained alumina bulk is used to develop alumina nanoparticles. Laser ablation is the preferred method for the production of nanoparticles because of its versatility in nanoparticle size and the different media. The used nanoparticles are mostly pure. On interaction with the solid, the laser beam produces a plasma and evaporates to molecules and their clusters.

Formation of fumes

A fume is produced by the evaporated particles and it is expanding with time. On further expanding, it interacts in the setup with an ambient gas or a different fluid that meets with it for forming alumina nanoparticles. X-ray diffraction (XRD), transmission electron microscopy (TEM), and emission spectroscopy were then used to analyze the nanoparticles for characterizing the collected type of nanoparticles.

 

Applications of Aluminum Oxide Nanoparticles

Drug delivery

Aluminum nanoparticles have been utilized in ordered mesoporous aluminum oxide’s form to enhance Telmisartan’s oral delivery as a poor-water soluble compound. Telmisartan is an anti-blood pressure drug. Evaporation induced self-assembly method synthesized ordered mesoporous aluminum oxide. X-ray diffraction (XRD), scanning electron microscopy, and Fourier transforms infrared then characterized it and then its pores were loaded with Telmisartan through the usage of a solvent impregnation method. Loading efficiency of 45% was seen between the nanoparticles and the drug in results. Moreover, when ordered mesoporous aluminum oxide was being loaded, it led to the release of Telmisartan and its major dissolution.

Aluminum oxide-ibuprofen nanocomposite’s sol-gel was fabricated in another study for increasing ibuprofen’s bioavailability. This was the reason for the fabrication of nano-aluminum oxide by aluminum oxide alkoxide’s controlled hydrolysis, followed by loading of the nano-aluminum oxide particles with the ibuprofen that’s insoluble in water. Then, Thermogravimetric analysis, Fourier transform Raman spectroscopy, Emmett and Teller method, Brunauer, UV-Vis spectrophotometry, and XRD analysis was used to characterize the prepared nanocomposite.

Effect on solubility

In sol-gel nanocomposite’s form with the aluminum oxide, there was a major increase in ibuprofen’s solubility and controlled release. The main mechanism and reason behind these significant increases is some of the characteristics of the sol-gel nano-aluminum oxide’s surface for instance high density of hydroxyl groups, highly porous structure, and high surface area. In this study, the major revelation is of the suitability of the nano-aluminum oxide particle of this type as an efficient and effective drug delivery vehicle.

Biosensing

There have been recent reports on the usage of aluminum nanoparticles as novel platforms to detect various molecules. Aluminum oxide nanoparticles are utilized for sensing bovine serum albumin. Self-assembled anodic aluminum oxide modified LSPR (localized surface plasmon resonance) sensor’s surface for performing the biosensing. In self-assembled anodic aluminum oxide, a well-organized aluminum oxide nanohole structure was produced on an LSPR chip. Nanocarbon-modified aluminum oxide nanocrystal’s shell/core was utilized in another study for sensing the DNA in a competitive bioassay. Easy surface engineering was enabled by this carbon layer and that’s why it was utilized as a platform for increasing aluminum oxide nanocrystal’s surface reactivity, biocompatibility, and stability.

Florescent nature of aluminum oxide

Aluminum oxide nanostructures and their fluorescent nature was implemented for various detection purposes like in vitro DNA detection, intracellular cargo monitoring, and cell imaging, for the purpose of them being used in biosensing applications. Moreover, there have been reports that aluminum nanoparticles have the ability of sensing chemicals. Just like this feature, aluminum oxide nanoparticles are also utilized with chitosan for detecting phenolic molecules as a nanocomposite. Aluminum nanoparticles were decorated on a chitosan film and then fabricated nanocomposite was loaded with horseradish peroxidase (HRP).

Cancer therapy

A modified pulse anodization process was used to fabricate aluminum oxide nanomaterial in the nanotubes’ form containing Thapsigarin, they were then loaded with Thapsigarin. An autophagy inhibitor, 3-methyladenine co-administered Thapsigarin for targeting autophagy signaling in both the normal and the cancerous cells. Aluminum oxide nanotube loaded with Thapsigarin displayed no cytotoxic effect in the normal cells however in the cancer cells, it induces autophagy signaling, referring to the ability of the aluminum oxide nanotubes for anti-cancer therapy as a new generation of the drug delivery vehicle. There have been reports on the anti-cancer characteristics of the spherical nano-aluminum oxide particles other than their suitability for cancer therapy. Rajan Y.C. et al. fabricated poly-glutamic acid-modified aluminum nanoparticles in this study and implemented them as cytotoxic agents for inducing the death of the cell in the prostate cancer cells. Aluminum nanoparticles displayed cell toxicity towards the treatment of PC-3 prostate cancer cells.

Surface potential and viability

In another study, increased surface zeta-potential was shown by the nano-petal AlNPs-treated mouse neuroblastoma Neuro-2a cells towards the negative values along with decreased viability. The shape of the utilized aluminum oxide nanostructures determines the zeta potential’s value and cell viability’s percentage. Cell toxicity of the highest level was showed by nano-petal aluminum oxide, followed by wedge-like nanoparticles and nanoplates. Aluminum nanoparticles showed the highest change in cell surface’s zeta potential.

AINPs are also utilized as an adjuvant in cancer immunotherapy in vivo and in vitro as an enhanced cancer treatment strategy in which aluminum nanoparticles were utilized as a cancer antigen carrier to dendritic cells’ autophagosomes, effectively presenting the delivered antigens to the T-cells. AlNPs applications lead to a major increase in the amount of the activated T-cells, resulting in provoking a significant cancer remission and potent anti-tumor activity of these cells. Moreover, it is proved in this study that when it comes to boosting cancer vaccines’ efficacy, the potential candidate is AINPs.

Anti-microbial effects

Aluminum nanoparticles exhibit strong antimicrobial activities due to their large surface area. Sadiq M. et al. proved aluminum nanoparticle’s anti-Escherichia coli (E. coli) property in his study, in which bacterium E. coli incubated 179 nm-sized-AlNPs of different concentrations. Scientists observed a mild anti-growth effect because of the electrostatic interaction between the bacterial cells and the nanoparticles. Moreover, a small decrease was seen in the bacterium’s extracellular protein content. In another study, aluminum nanoparticles displayed anti-growth effects which were originated from nanoparticle’s direct attachment to these bacterial cell walls.

Aluminum oxide as a silver nanocomposite

When utilized in aluminum oxide–silver nanocomposite’s form, great antimicrobial characteristics are shown by the aluminum oxide nanomaterials against Staphylococcus epidermis (S.epidermidis) and E.coli, which refers to the nano-aluminum oxide’s potential biomedical applications as the composite structures.

There was another research in which aluminum oxide nano-coatings, in the form of aluminum oxide core/Fe3O4/shell magnetic nanoparticles, displayed remarkable magnetically-derived photothermal killing effects on various drug-resistance, gram-positive and gram-negative bacterial isolates. The aluminum oxide shell is a recognizer of bacterial cells in this intelligently designed nanocomposite. Although, the Fe3O4 core subsequently kills the bacterial cells photothermally. In addition, a magnetic field is used to use the core Fe3O4 for guiding the nanoparticles towards the bacterial cells.

Treatment of other diseases

Vasoactive intestinal peptide conjugated Alpha-Aluminum nanoparticles and was utilized as anti-asthmatic nano-drugs for preventing the mouse model from getting allergic asthma. The vasoactive intestinal peptide was protected against enzymatic degradation in the asthmatic mouse model’s lung by using alpha-aluminum nanoparticles, and they displayed a strong anti-asthmatic activity than the non-conjugated vasoactive intestinal peptide and beclomethasone.

Nano-thrombolytic system has been used to explain AINPs’ potential advantages. AINPs sol-gel form was loaded with the thrombolytic enzyme streptokinase for showcasing this potential. When they have a size of less than 500 nm, an efficient and effective thrombolytic activity was seen on various samples by prepared streptokinase-aluminum nanoparticles along with streptokinase’s sustained release.

Bimolecular preservation and stabilization

According to Volodina V.K. et al’s study, protein molecules can be correctly folded by the aluminum nanoparticles and they can be the nano platform for that. Aluminum nanoparticles interact with the denatured negatively charged proteins electrostatically for being utilized as a renaturing material. They also prevent the misfolding and aggregation of the denatured negatively charged proteins. Until the un/misfolded protein folds correctly, the refolding process is kept under control by the aluminum nanoparticles in addition to the reaction.

Immunotherapy

A major target of next-generation vaccines and immunotherapy is autophagy induction because of autophagy’s central role in presenting the antigens to the T lymphocytes. AINPs have been researched as an autophagy inducer because of this reason. Cysteine peptidase A and B were conjugated in one study to Aluminum nanoparticles and they were utilized as leishmania vaccine for inducing autophagy in the macrophages. When these nanoparticles were administered, fast internalization is shown of the conjugated nanoparticles by leishmania-infected macrophages. Aluminum nanoparticles can also be used to design an anti-HIV vaccine as they are effective and efficient nano-adjuvants to provoke mucosal and systematic immunity. A peptomer was covalently conjugated onto the aluminum nanoparticles, leading to a nanoconjugate of 300 nm that can cause a strong immunologic reaction in mucus.

Pharmaceuticals

The nanoparticles are still being utilized for drug delivery purposes in various fields of medicine. Dosage’s accuracy determines the nanoparticle’s power in delivering the drugs into the body and they can release it in very certain locations at a set time in the body, which leads to fewer side effects as the drugs’ therapeutic efficiency will increase. Fewer side effects will be caused as compared to the number of side effects that will be caused if current methods are used for the delivery of the drug.

Alumina nanoparticles are a good option for IV delivery of the drug into body parts because of their durability. The durability of the nanoparticle matters here as such body parts has extremely low pH, making it easy to degrade the nanomaterials before nanomaterials reach their desired location. The most concerning thing right now is aluminum toxicity as recently people have been linking cancer and aluminum. However until now, aluminum has shown no carcinogenic effect so that link has not been proven, still one should take care while adding aluminum nanoparticles for delivery of the drug.

 

 

Advantages

AINPs are attractive and efficient nanomaterials because of a number of their great characteristics. Some of them are mentioned below:

(i) Due to having known methods of manufacture, they are easily available.

(ii)They can be easily conjugated with molecules of other origins like biological and chemical molecules because of their vast surface area.

(iii) AINPs can interact easily with biological interfaces, enabling them to be utilized for biological purposes.

(iv) In harsh, complicated non-biological environments and other numerous conditions, AINPs are stable enough for being utilized.

(v) They are ideal nanomaterial when it comes to developing various nanomaterials because of the fact that their surface functionalization protocols are very clear.

Conclusion

Aluminum oxide nanoparticles have gained popularity and prominence in the field of biomedical specifically as they are serving this field for a long time. This enables these nanoparticles to fight and combat a series of deadly diseases as well which is a huge achievement for such tiny particles. Their excellent nature in which they are present and then molded into the form that can be used for beneficial purposes is a very hard and tiring process but once achieved can work wonders for the industries as well as the humans.

Boron Doped Graphene and its application as electrode material for supercapacitors

Graphene particles are by far the best-known particles that are serving as one of the best catalyzers in the industry. When boron is doped with graphene by going through different processes it becomes and forms boron-doped graphene particles which serve various purposes in the industry.

The characteristics and properties which are exhibited by boron-doped graphene particles are highly rich in their content and are capable of exhibiting a lot of valuable processes. Technological applications have only increased over time and enhanced the entire purpose of forming these boron-doped graphene particles.

Introduction

Graphene-based nanomaterial, boron-doped graphene (BG), is a carbon atom’s single sheet organized in a hexagonal lattice. When the boron atom impurities are added into pure graphene, the bandgap opens, redox reactions accelerate, catalytic ability enhances, and the activation region on its surface increases. All of these alterations give various applications to it in sensors, ultracapacitors, semiconductor devices, fuel cell chemistry, and other technologies.

 

Graphene doping

Using electron-withdrawing (boron) or electron-donating groups (phosphorus, nitrogen), to dope graphene is significant to change graphene’s electrical characteristics. Graphene sheet’s electron density changes when they are doped with electron-withdrawing (electron acceptors, p-type) or electron-donating (n-type, electron donors) groups and thus also affects graphene sheet’s electrochemical characteristic. Doping level plays a very important part as carrier density is very significant to tune the material’s performance.

One of the other major problems is manufacturing doped materials for synthesizing scalable methods to doped material’s large quantities. In this article, a technique is showed for the scalable formation and tunable doping levels by graphene oxide’s exfoliation at various temperatures in the BF3 atmosphere. There are also investigations on p-doped material’s electrochemical characteristics and their comparison with the ones that the literature presents.

Nitrogen and boron-doped graphene

Unusual electrocatalytic effects are displayed by nitrogen-doped graphenes toward oxygen and H2O2 reduction which have extremely significant usages for applications in fuel cells and biosensing. In comparison with graphene, large capacitance is possessed by nitrogen-doped graphenes. Similar effects were displayed by boron-doped graphene, being increased capacitance and electrocatalytic toward oxygen reduction. According to observations, it doesn’t matter which atoms are doped in graphene as these characteristics are improved. Compound oxidation is easy with increased doping of materials with electron-deficient components, whereas reduction turns difficult.

These observations are contrary to the old reports on the boron-doped graphene that catalyzes the oxygen’s electrochemical reduction. Cyclic voltammetry, prompt γ-ray analysis, X-ray photoelectron spectroscopy, Raman spectroscopy, and scanning electron microscopy, are used to characterize it in detail.

Preparation

Graphene oxide’s thermal exfoliation was done to manufacture boron-doped graphenes in an atmosphere at 1000 °C in N2, 800 °C in N2, and with boron trifluoride diethyl etherate in N2/H2 at 1000 °C. Graphene oxide goes through many stages, exfoliation, deoxygenation (manufacturing CO2, CO, H2O, organic molecules), and then its simultaneous doping with boron. Cyclic voltammetry (CV), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and prompt γ-ray analysis (PGAA), are used to characterize resulting boron-doped graphenes for studying the electrocatalytic characteristics of it towards oxygen reduction and its capacitance. Here, there are all abbreviations of all boron-doped graphenes as B-G.

Thermal shock treatment

There were investigations on the Graphene oxide’s thermal shock treatment in the BF3 atmosphere and how it results in Graphene oxide’s exfoliation. SEM studied boron-doped graphene’s (B-G) morphology. SEM images are shown of boron-doped graphenes and those graphenes are made by exfoliation. A typical exfoliated structure is shown by all of these materials just like how it was shown in previous studies and this structure also assures graphite oxide’s successful thermal exfoliation in the BF3 atmosphere. Exfoliation temperature’s effect was consequently studied upon the amount of graphene used to dope boron through PGAA. (prompt γ-ray analysis)

Trace levels of elements

One of the best methods to determine the element’s trace level is PGAA. Boron’s absolute content in samples was determined comparatively to the liquid standard of H3BO3 with the known concentration of boron. In N2/H2 atmosphere, graphite oxide’s exfoliation at 1000 °C resulted in graphene’s doping at 23 ppm boron levels, whereas boron’s larger amount was introduced on graphite oxide’s exfoliation in the atmosphere of nitrogen, 590 ppm at 1000 °C, and 140 ppm boron at 800 °C.

According to the result, graphene can be doped with boron atoms of a higher amount if the exfoliation temperature was higher. A major decrease was observed in the concentration of boron for GO exfoliated in the atmosphere with hydrogen. Thus, boron’s successful doping into the graphene sheets is confirmed by this result.

Characterization of density

Raman spectroscopy is used by us for characterizing the defect density in boron-doped graphene by determining the doping level that boron did on Graphene. Defects are present and indicated by the D band at almost 1350 cm−1 because of the sp3 -hybridized carbon atoms. A G band is shown by the graphene sheet’s pristine sp2 lattice carbon atoms at almost 1560 cm−1. The carbon structure’s degree of the disorder can be indicated through the usage of the ratio between D and G band intensities (ID/IG). 0.732, 0.632, and 0.903 are the ID/IG ratio for 590 ppm B-G, 140 ppm B-G, and 23 ppm B-G, respectively.

Sizes of crystallites

D- and G- band intensities can be used to estimate various material’s average crystallite sizes (La) by applying this equation, 1.20 =× × × λ − L II 2.4 10 / a 10 laser 4 G D. In this equation, ID and IG are Raman D and G band’s intensities, and the excitation laser’s wavelength is denoted by λlaser in nanometers. The crystallite sizes in graphenes that are doped with boron are then calculated. La is 23.0 nm of 590 ppm B-G, 26.6 nm of 140 ppm B-G, and 18.6 nm of 23 ppm B-G. At 2700 and 1620 cm-1, both the 2D band and D’ band are displayed by all three boron-doped graphenes indicating disorder of low degree in their carbon structure.

XPS was used to consequently determine boron-doped graphene’s elemental compositions as it is a chemical analysis method and is beneficial for determining the bonding arrangement and the elemental composition. The obtained high-resolution XPS of C 1s and wide scan of C 1s for three graphenes referred to the fact that there was a removal of most of the oxygen-containing groups and the preparation of the thermally reduced graphenes was successfully done.

Obtained ratios

According to wide scan XPS, for 590 ppm B-G, the C/O ratio is 16.1, for 140 ppm B-G, the C/O ratio is 8.9, and for 23 ppm B-G, 14.2 is the C/O ratio. Huge insight is given of the residual oxygen-containing group’s chemical composition by high-resolution XPS of the C 1s signal. They exhibit different and various energy levels. When made at 800 °C in N2, 1000 °C in N2/H2, and 1000 °C in N2, boron-doped graphenes possess C-C bonds, C−C bonds, C−O bonds, CO bonds, and O−CO bonds, respectively. XPS can determine the residual oxygen-containing groups in the reduced graphene. However, trace amounts of boron can’t be measured by XPS as it is not sensitive enough.

Combustible elemental analysis

Boron-doped graphene’s elemental composition can be determined by using combustible elemental analysis as it is very beneficial for measuring the accurate content of combustible elements present in the bulk material. Further, more insight regarding the bonding character and composition of graphene sheets is provided when it is combined with XPS. 5.54 atom % of O, 9.63 atom % of H, and 84.83 atom % of C, was contained by 590 ppm B-G. 7.69 atom % of O, 10.03 atom % of H, and 82.28 atom % of C were contained by 140 ppm B-G. 7.48 atom % of O, 10.04 atom % of H, and 82.48 atom % of C were contained by 23 ppm B-G. Moreover, there was no nitrogen in any of the samples.

Electrical resistivity

Four-point measurements of compressed tablets studied resulting boron-doped material’s electrical resistivity. 13 ppm B-G, 140 ppm B-G, and 590 ppm B-G, has the electrical resistivity of 9.5 × 10−5 Ωcm, 2.1 × 10−5 Ω cm, and 2.3 × 10−4 Ωcm. According to these results, the electrical resistivity is increased by boron’s higher content which is in accordance with boron’s electron acceptor characteristics. There was an investigation on the boron-doped graphene’s electrocatalytic activity toward oxygen reduction reaction (ORR). In both N2 saturated 0.1 M KOH aqueous solution and air, cyclic voltammograms were recorded at 3 of the boron-doped surfaces. A major reduction peak is observed. There was no electrochemical reduction in N2- saturated KOH solution, and the reduction peak for air-saturated KOH solution was ∼−460 mV.

Cyclic voltammograms

Oxygen’s reduction originates ∼−460 mV reduction peak. Reduction of oxygen with different levels of doping was recorded by Cyclic voltammograms. For Graphenes with boron dopant’s increasing concentrations, reduction peak shifts to increasingly negative potentials. Thus, for boron-doped graphene, the electrocatalytic activity towards the reduction of oxygen would be lower if the doped boron atoms are more, and vice versa. This is in agreement with hole-doping electrochemistry’s general concept but also in contrast to the past observations.

Weight specific capacitance

Cyclic voltammetry capacitive charge-discharge current was used to determine the boron-doped graphene’s weight-specific capacitance. ν C = I (2), is used to express the capacitance. In this equation, ν is the scan rate (mV/s, can be expressed as dE/dt), I is current (A), and C is capacitance (F). There were investigations on the capacitances of boron-doped graphenes. The investigations were being done by measuring the current With scan rates of 400, 200, 100, 75, 50, and 25 mV/s and at 0.15 V of applied potential. Boron-doped graphene’s weight-specific capacitances are 10.3, 10.7, and 11.7 at 1000 °C in N2, 800 °C in N2, and at 1000 °C in N2/H2. These weight-specific capacitances refer to the fact that when the amount of doped boron atoms increases, the weight-specific capacitance decreases.

In comparison to non-doped parts

As compared to its non-doped counterparts, N-doped graphenes and B-doped graphenes exhibit higher capacitance contrary to the previous claims. No theoretical background explanation is present here whereas, in both hole and electron doping cases, improved capacitance should be expected. In Han et al.’s paper, the utilized method was based on a famous hydroboration reaction from organic chemistry. With the BH2 group being covalently bonded to the backbone of graphene, the production of sp3-hybridized carbon can be imagined from such a reaction’s mechanism. Attaining carbon’s direct substitution with boron through the methods that Han et al. presented, is impossible.

Surface plasmon resonance

Optical sensors, surface plasmon resonance (SPR) biosensors, gained a lot of attention because of their benefits like non-invasive measurements, room temperature real-time measurements, and high sensitivity. At the metal-dielectric interface, SPR is very sensitive to refractive index alteration. Because of the analyte’s presence, sensitivity in detection is exploited if there is any kind of change at the interface. Typically in SPR biosensors, gold is utilized as a resonant layer because of its chemical stability, where a higher shift of resonant angle with a change in refractive index is exhibited by gold. Although, biomolecule’s adsorption or detection at low concentrations is extremely difficult or even impossible at times because of gold’s inertness.

Single crystalline gold surface

At increased temperatures and pressures or under high vacuumed (UHV) conditions, the single-crystalline gold surface doesn’t specifically measure small molecules adsorption. Such molecules are NH3, NO, O2, H2, and CO. There have been investigations of the physically and chemically modified gold layer in various studies regarding improved detection and adsorption mechanisms, like CNTs, gold nanocrystal, kinked/stepped gold surface gold nanorods, and graphene oxide coupled with gold nanoparticles.

Novel materials

There have been investigations on some of the novel materials like MOS2, Au/Ag/Au/chitosan-graphene oxide (RGO), and graphene, for improving SPR sensor’s selectivity and sensitivity. In all of these novel materials, the most promising material is graphene because of its excellent and remarkable characteristics like high surface-to-volume ratio and high mobility that are advantageous for biomolecule’s effective adsorption in comparison with gold. An improved SPR response is displayed by the doped graphene oxide (GO) that is enriched on the gold layer’s top with abundant defect sites. Although, chemical doping causes the modulation of the optical bandgap and GO’s Fermi energy which leads to alteration in the optical characteristics like dielectric constants and refractive index. SPR sensing techniques can monitor these variations.

 

Enhancements in graphene’s characteristics

According to recent literature, huge enhancements have been seen in the characteristics of graphene by doping graphene with various heteroatoms like Boron (B), Nitrogen (N), Oxygen (O)< and Fluorine (F). In numerous applications like improved photogenerated catalysis, solar cells, Li-ion batteries, and supercapacitors, there have been reports of the boron-doped graphene oxide. Also, numerous methods like chemical vapor deposition (CVD), arc-discharge process, and hydrothermal method have been used to dope graphene-based materials, where for tuning graphene’s electronic and optical characteristics, stable atomic substitution with carbon is extremely required. At high temperatures, GO is mostly lessened thermally among the reduction methods. Although, high-density defects are produced by reduction at high temperatures on the basal planes and edge, deteriorating graphene’s optical and electrical characteristics.

Catalyst deposition

In post-treatments, there were decorations of each of the as-synthesized materials with platinum catalyst nanoparticles of 60 wt % that were made in the already reported procedure by utilizing a metal-organic Pt (acac) 2 precursor. The powdered support materials were briefly mixed uniformly in a glass vial of 4.5 mL with Pt(acac)2 in suitable ratios for yielding 60 wt% Pt. The mixture was heated under a low vacuum of 600 Torr for 16 hours at 210 C in an N2-H2O atmosphere, resulting in Pt metal nanoparticle’s deposition onto the support.

Cell fabrication

An anode-supported configuration was used to fabricate solid acid fuel cells. Mesh discs of 2.85 cm2 of Sintered 304 stainless steel functioned as the anode current collectors. There have been some previous reports on the architecture of the cell and after this, it was confirmed as the architecture of this cell was completely identical to the one in previous reports. CDP’s mechanical mixture formed identical anodes with 1.0 mg/cm2 (Pt) Pt loading. For all of the tested cells, those identical anodes with a Pt loading of 1.0 mg/cm2 (Pt), inhouse synthesized 60 wt% Pt supported on naphthalene (a fugitive binder), and carbon black (Cabot Crop., Vulcan XC-72R), by weight, in a 3:1:1 ratio.

A CDP membrane was possessed by each cell. The membrane’s thickness was 50 μm, and it was laminated at 125 MPa to the anode. Experimental cathodes of 25 mg of a 3:1 by CDP’s weight mixture and 60 wt% of Pt supported on CB9Ar, CH5Ar, or SWCNHs were implemented at 30 MPa pressure to the dense CDP membrane. 1.3 mg/cm2 was the experimental cathode’s areal Pt loading.

Electrochemical testing

At 250 C temperature, ultrahigh purity H2 and the air was used to conduct cell testing by utilizing stainless steel test rigs, each at 75 C dew point. Bio-Logic VSP potentiostat was used to record polarization curves from open circuit potential to 0 V by scanning the cell potential at 10 mV s-1. At 0.8 V, each cell faced a multi-step cyclic testing protocol which included potentiostatic electrochemical impedance spectroscopy (EIS) spectrum for attaining the average high-frequency area-specific resistance (ASR), polarization curve’s recording, at 0.6 V a 30-minute potentiostatic hold, and then this protocol repeated. At 0.6 V, the cells were held after 30 cycles.

The polarization curves were corrected by using ASR for effects of membrane ohmic resistance, yielding iR-free polarization curves. For the formulation of each cathode, the results were averaged across multiple cells comprising two replicates at least.

Characterization methods

There were performances of electron energy-loss spectroscopy (EELS) and transmission electron microscopy (TEM) imaging in a Zeiss Libra 200MC (0.1 nm is the information limit). ImageJ software was used to make an estimate of the dimensions of the nanoparticle from the TEM micrographs for calculating their cross-sectional areas and for tracing their parameters. There were derivations of the same area’s effective nanoparticle diameters. There have been many reports on the standard deviations and mean dimensions.

Sizes of the flake were measured by using a similar procedure, but by utilizing the square approximation. The concentration of the boron was determined by using EELS, and the background spectra were fit by utilizing the combination of a polynomial model and a power law. A polynomial model is, E−r + aE2 + bE + c, where E is energy, whereas r, c, b, and a, are fitting parameters. An In-lens detector was used to perform scanning electron microscopy (SEM) imaging at 3kV with a Zeiss Auriga 40. Pore size analyzer and Quantachrome Micromeritics surface area were used to perform BET surface area analyses. At 10 C/min ramp rate in air, Q50 from TA instruments was used to perform thermogravimetric Analysis (TGA).

Moreover, a continuous scan was done to carry out X-ray diffraction (XRD) measurements on a two-circle high-resolution X-ray powder diffractometer through the usage of Cu-Kα1 radiation (1.54059Å) with ½° fixed divergence slit.

Raman spectroscopy

A custom microscope-based system was used to perform Raman spectroscopy at 532 nm of excitation wavelength. The laser beam was focused by using a 100X objective with ~1 μm spot size on the sample, and ~0.5 mW was the measured power of the laser at the sample location. Spectral peak fitting was applied along with Gaussian/Lorentzian line shapes.

Conclusion

A lot of detailed processes are carried out to form these boron-doped graphene particles which are not only serving in the technological industries but are also paving way for the upcoming technologies which can be buckled up by the use of boron-doped graphene particles. Hence, these are excellent means of promoting technology and technology-based industries.

Lithium Hydroxide Monohydrate Application Areas

Lithium hydroxide monohydrate is also known and written as LiOH.H2O which is basically the combination of lithium, hydrogen, and oxygen. The structure of lithium hydroxide monohydrate consists of crystal x-rays and even neutron diffraction as well. All these three elements, when combined together, form a strong bond that is very unique in its nature owing to the excellent properties of lithium, hydrogen, and oxygen combined.

The properties of lithium hydroxide monohydrates are extremely beneficial for the industries that these become a part of and that is why the applications of lithium hydroxide monohydrates have massively increased over the past years. Their application areas vary in nature but are proven beneficial for the market. The combined application areas of lithium hydroxide monohydrate are briefly explained in this article which further elaborate the efficiency and efficacy of this compound.

Introduction

The occurrence of hydrates takes place in a broad range of compounds from pharmaceuticals to concrete and minerals. The characteristics and the behavior of the compounds are markedly altered by the water’s presence in the compounds. In the vibrational spectrum, the bands’ intensity, width, and changes in their position reflect the hydrogen bonding’s strength. Specifically, this is for the water librational modes and there has been a huge amount of detailed studies on them for a big amount of cases.

Useful test case

A useful test case is provided by the lithium hydroxide monohydrate, LiOHH2O, for assigning water librational modes. Both neutron diffraction and single-crystal x-ray determine the structure. When it comes to vibrational spectroscopy, LiOHH2O is subsequently a specifically interesting subject due to the possibility of isotopic substitutions on all 3 elements, both Raman and infrared spectroscopy have been used to study it.

Spectra’s interpretation

Although, all of the modes have not been observed and the spectra’s interpretation is controversial with no consensus as to the assignments. Instead of the hydrogen bonds linking water molecules and hydroxyl ions, OH−H+OH− units made up the structure according to the studies of Raman and infrared study. H-O-H bending and O-H stretch in the Raman spectrum is the reason for the absence of modes on which this interpretation was based. Despite it not being uncommon, no evidence is shown by the K2[FeCl5(H2O)] Raman spectrum for water’s presence.

Comparison with crystal structure

As compared to the crystal structure that the single-crystal neutron diffraction determines, the proposed structure is at variance clearly, displaying discrete H2O- and OH− entities. A high water-insoluble crystalline lithium source, lithium hydroxide monohydrate is for usages that are compatible with higher (basic) pH environments. When the oxygen atom bonds to a hydrogen atom, the OH-, hydroxide is usually present in nature and is most typically and extensively studied and researched molecules in physical chemistry.

 

Characteristics and usages

There are diverse characteristics and usages of the hydroxide compounds, starting from base catalysis and all the way to detecting carbon dioxide. At JILA (the Joint Institute for Laboratory Astrophysics), scientists used hydroxide molecules to obtain compound’s evaporative cooling for the first time in a watershed 2013 experiment, a discovery that can result in new methods to control chemical reactions and can affect broad disciplines, including energy production and atmospheric science technologies.

Availability in different volumes

Generally, there is the immediate availability of the lithium hydroxide monohydrate in most volumes. Nanopowder, submicron, and High purity forms may be considered. There are often problems in the assignment of the water librations to individual motions. Rock > wag > twist is the typical order which is expected based on the moments of inertia. There is no frequent observation of the twist in the Raman or infrared spectra and it is suggested that the 796 cm−1 INS band can be assigned to this mode. According to a simplistic assignment, the twist is the 796 cm−1 band, the wag is the 872 cm−1 band and the rock is the 1038/988 cm−1 bands, having the virtue of being consistent with the spectra and agreeing with the previous assignments.

INS spectroscopy

INS spectroscopy has a significant benefit and that is that it can quantitatively calculate the intensities. This is possible by utilizing the atomic displacements or by utilizing a classical “balls and springs” force field approach in each mode that the vibrational analysis generates from an ab initio calculation. A reasonable agreement has been given by making the initial efforts that utilized the classical approach and a model consisting of 2 formula units with the observed INS spectrum. Although, similar INS intensity (as there are similar amplitudes of vibration) is possessed by all three water librational modes, therefore reaching an unambiguous assignment wasn’t possible.

The initial calculations

Ab initio calculations of the complete unit cell have been carried out for overcoming this difficulty by utilizing the periodic-DFT code, CASTEP. There have been comparisons of both geometry and lattice optimization and geometric parameters for the structure optimized at the experimental lattice parameters. A small ∼2% increase in the cell volume along with an increase in the parameters of the cell occurs due to the lattice optimization. In 2 calculations, the intramolecular bond angles and distances are the same and in agreement with experiment t (0.5◦for the angle and <0.02 Å for distances).

Intermolecular angles and distances

There intermolecular angles and distances are extremely close, and due to the increased size of the cell, optimized lattice calculations are a little larger. Ab initio MO-LCAO-SCF calculations also determine the electron density in LiOH.H2O. The calculations explicitly include all closest neighbors to the OH-ion and H20 molecule; point charges have simulated more distant and next-nearest neighbors. There are comparisons of the theoretical electron density maps with the experimental maps.

Findings

According to the findings, intermolecular bonding’s influence in the crystal is twofold. At first, the OH- ion’s and H2O molecule’s total polarization is majorly increased. Then, in OH- and H2O-, the electron density around the O nuclei is reorganized, resulting in a less density in the lone-pair directions. A significant role is played by the lithium hydroxide monohydrate, particularly in the making of the lubricating greases. It’s utilized in producing glass, specific ceramic products, and cathode material for lithium-ion batteries too. It also possesses applications in the purification of air because of its carbon dioxide-binding characteristics.

Lithium-ion batteries

Mainly, lithium hydroxide is consumed for lithium-ion batteries like lithium iron phosphate and lithium cobalt oxide (LiCoO2) in the production of cathode materials. It is preferred as a precursor for lithium nickel manganese cobalt oxides over lithium carbonate.

 

If you want to obtain more information about lithium-ion batteries,

you can read our other blog post.

Grease

Lithium 12-hydroxy stearate is a famous lithium grease thickener, that forms a general-purpose lubricating grease because of its usefulness at various temperatures and its high resistance towards the water.

Carbon dioxide scrubbing

Lithium hydroxide is utilized for rebreathers, submarines, and spacecraft in breathing gas purification systems by producing water and lithium carbonate for eliminating carbon dioxide from the exhaled gas.

2 LiOH•H2O + CO2 → Li2CO3 + 3 H2O

In spacecraft, anhydrous hydroxide is preferred for its lesser water production and lower mass for respiratory systems. Carbon dioxide gas of 450 cm3 can be removed by anhydrous lithium hydroxides of one gram. At 100-110 degrees celsius, monohydrate loses its water.

Precursor

Combined with lithium carbonate, lithium hydroxide is the main intermediate that is utilized to produce other lithium compounds, and that is explained by its usage in the formation of lithium fluoride.

Other usages

Its usage can be seen in some Portland cement formulations and ceramics. Lithium hydroxide is utilized for alkalizing the reactor coolant for corrosion control in pressurized water reactors as it is isotonically enriched in lithium-7. It’s good radiation protection against free neutrons.

Structural Changes during lithium hydroxide monohydrate’s Carbonation

During lithium hydroxide monohydrate’s carbonation in CO2’s presence with increasing temperature, major changes in the structure are evident. On heating, lithium hydroxide’s dehydration is confirmed from the reduction in the characteristic peak’s intensity that corresponds to CuKα 2θ = 33.54◦ (h k l: (−2 2 0)) or d = 2.67 Å, q = 2.35 Å−1. On heating to more than 70 ◦C of temperatures, lithium hydroxide monohydrate’s dehydration is fast, and on heating to more than 108 ◦C, the characteristic peak disappears. Lithium hydroxide’s highest integrated intensity is 147 degrees celsius, and on further heating, it decreases.

Temperature variations

At more than 250 degrees celsius of temperatures, a major reduction is noted in the characteristic lithium hydroxide peak. Almost around 450 degrees celsius, the characteristic lithium hydroxide peak collapses. At 59 ◦C, the lithium carbonate peak’s appearance is concurrent with lithium hydroxide monohydrate’s dehydration for producing lithium hydroxide. As the temperature of the reaction increases from 71 ◦C to 499 ◦C, the characteristic lithium carbonate peak increases in intensity too. When the temperature increase to 450 degrees celsius, the characteristic lithium carbonate peak’s integrated intensity increases too, and after that increase, it stays comparatively unchanged. At 450 C or above temperatures, lithium carbonate’s comparatively unchanging integrated intensity peaks.

Thermal energy storage technologies

Recently, thermal energy storage technologies have been considered to be a significant part of alternative energy’s efficient utilization as they turned out to be more and more attractive because of global warming and fossil energy consumption. Chemical heat storage, latent heat storage, and sensible heat storage are the three main types that are included in these technologies. A role is played by all of these technologies in the solving of the thermal energy’s demand and supply mismatching and enhancing energy efficiency.

Thermochemical heat storage

Thermochemical heat storage utilizes reversible chemical reactions for storing and releasing thermal energy, and it is among these technologies as it is more appropriate to efficiently utilize thermal energy because of thermochemical material’s high heat storage density. Generally, thermochemical heat storage can be divided into 2 parts based on the heat storage working temperature: low-temperature heat storage ((<200 ◦C) and high-temperature heat storage (200–1100 ◦C). There has been a selection of a large number of thermochemical materials (TCMs) as one of these technologies’ core parts.

Example

For example, for the purpose of high-temperature thermochemical heat storage, metal carbonates, metal hydrides, and metal hydroxides can be utilized as TCMs however salt ammoniate and inorganic salt hydrates are thought of as the best candidates for the low-temperature thermochemical heat storage because of their various decomposition temperatures. The most promising candidate was the inorganic hydrate LiOHH2O for efficiently storing low-temperature thermal energy, as it has a mild reaction process and high energy density of 1440 kJ/kg. Although, the pure LiOH•H2O’s both thermal conductivity and hydration rate, just like the other inorganic hydrates are still low, seriously limiting this material’s application. Thus, preparing heat storage composite TCMs with high thermal conductivity and strong water sorption holds great significance.

Carbon nanospheres and nanotubes

Typically, both the carbon nanospheres (CNSs) and carbon nanotubes (CNTs) are carbon nanomaterials, and they possess chemical stability, low bulk density, high thermal conductivity, and large surface area, and they are utilized broadly in various fields like latent heat thermal energy storage, catalysis, and electronics. Like a traditional macro carbon material, many good characteristics are shown by the activated carbon (AC) too like low density, high stability, and high adsorption capacity, which are utilized commonly for catalyst synthesis and gas adsorption. Moreover, after the surface oxygen groups are introduced, all these carbon materials have remarkable hydrophilic characteristics.

 

Application

Although, until now the application of carbon nanomaterials is only done rarely in manufacturing inorganic hydrate-based TCMs. In this work, there was the preparation of TCMs of four kinds (LiOHH2O/AC, LiOHH2O/MWCNTs, LiOHH2O/CNSs, LiOHH2O) for investigating carbon nanomaterial’s effect on lithium hydroxide monohydrate’s thermal energy storage performance. Activated carbon-modified LiOHH2O (LiOHH2O/AC) and pure LiOHH2O are among these samples that were obviously utilized as the control groups for displaying the carbon nanomaterial-modified LiOHH2O’s benefits.

The Microstructure Characterization of Lithium Hydroxide Monohydrate-Based TCMs

LiOHH2O were well dispersed on AC, MWCNTs, and CNSs according to the broad diffraction peaks of LiOHH2O/AC, LiOHH2O/MWCNTs, and LiOHH2O/CNSs. It was confirmed from the SEM analysis that there was a successful synthesis of MWCNTs with 100nm of diameters and the highly uniform CNSs with 200 nm of diameters. The bulk LiOHH2O was aggregated with large diameters of 300 nm–1 µm before carbon additives doping. On carbon nanotubes and carbon nanospheres surface, the LiOHH2O particles were well supported and dispersed.

Structure formations

Moreover, after LiOHH2O’s introduction, there was no obvious structure deterioration according to observations. Although, after LiOHH2O’s intervention, activated carbon’s surface was covered intensively. LiOHH2O nanoparticles with 20-30 nm of diameter were supported on the CNSs successfully with the clear particle structures. It was well-supported on the multi-walled carbon nanotubes, but some of the LiOHH2O nanoparticles were connected without a clear interface with others. The diameter of the nanoparticle was in 50-100 nm of range, and they were way larger as compared to those that are supported on the CNSs.

Observations

There were no clear observations of the LiOHH2O particles on the activated carbons for the LiOHH2O/AC sample. The pure LiOHH2O also existed in stacked flakes form. According to AAS characterization, around 50% was the LiOHH2O content of LiOHH2O/AC, LiOHH2O/MWCNTs, and LiOHH2O/CNSs. Intermolecular interactions like hydrogen bonding can exist between the LiOHH2O and additives during the manufacturing of LiOHH2O/AC, LiOHH2O/MWCNTs, and LiOHH2O/CNSs, because of the presence of oxygen-containing functional groups like carboxyl, carbonyl, and hydroxyl groups on the surface of AC, MWCNTs and CNSs. Thus, a good ability is shown by the composites for retarding the LiOHH2O’s aggregation with the proper additives supplying hydrogen bonding.

Nitrogen adsorption-desorption isotherms

Nitrogen adsorption-desorption isotherms also measured the porosity structures of LiOHH2O/AC, LiOHH2O/MWCNTs, LiOHH2O/CNSs, LiOHH2O, AC, MWCNTs, and CNSs. Different textures were displayed by the composed LiOH•H2O-based TCMs. As compared to the specific surface area of pure LiOHH2O (15 m2/g) and LiOHH2O/AC (84 m2/g), the specific surface area of LiOHH2O/MWCNTs (140 m2/g) and LiOHH2O/CNSs (276 m2/g) was higher because of the carbon nano additives larger BET surface area. It can be concluded from the results of TEM and SEM characterization that the significant factor was the high specific surface area and it can result in the form of LiOH•H2O particles nanoscale dispersion.

Lithium Hydroxide Monohydrate-Based TCM’s Heat Storage Performance Test

There were results of the performance tests which were carried out of pure LiOH.H2O/ MWCNTs, LiOHH2O/CNSs, LiOHH2O/AC, and LiOHH2O. According to findings, water vapor and lithium hydroxide’s reaction rate was slow and after 1 hour of hydration, LiOH’s conversion to LiOHH2O was only about 42%, which was calculated via H2O’s almost 18% mass loss. According to findings, 661 kJ/kg was the endothermic heat value of the LiOHH2O. CNS-modified LiOHH2O’s DSC curve can be seen. One can see that LiOH was hydrated completely to LiOHH2O after LiOH/CNSs 1 hour hydration, and, moreover, this 2020 kJ/kg or more could be reached by this sample’s heat storage density normalized by LiOHH2O content. A high level was reached by this LiOHH2O’s value that’s contained in LiOHH2O/MWCNTs.

Samplings

For the LiOHH2O/AC sample, as compared to the heat storage density of LiOHH2O/CNSs and LiOHH2O/MWCNTs, the LiOHH2O’s heat storage density was lower, and it reached 1236 kJ/kg. LiOH completely reacted with the H2O molecules and converted them to LiOHH2O than pure LiOH because of the addition of LiOH, AC, MWCNTs, and CNSs at the same duration of the reaction of hydration, as indicated. On the other hand, there was a significant enhancement of the hydration reaction rate of LiOHH2O/AC, LiOHH2O/MWCNTs, and LiOHH2O/CNSs. H2O adsorption could be made easy by the currently existing hydrophilic functional groups on the surface of AC, MWCNTs, and CNSs, and offer a totally different reaction interface between the water molecules and LiOH.

Heat storage density

Ultrahigh heat storage density was showed by the LiOHH2O/MWCNTs and LiOHH2O/CNSs composed TCMs, more as compared to that of the pure LiOHH2O TCMs and LiOHH2O/AC because of their higher specific surface area, that improved the dispersion of LiOHH2O nanoparticles substantially and increased surface area’s contact with the water molecules. Their lower heat storage density is maybe because of the pure LiOHH2O’s low specific surface area or the low specific surface area of LiOHH2O/AC.

The number of surface atoms would increase for sure when the size of the particle reached the nanoscale; thus, as compared to the surface atom’s binding energy and crystalline field, the internal atoms had a different binding energy and the crystalline field, and it had various dangling bonds because of less adjacent atoms. Better thermodynamic characteristics are shown by the nanoparticles because of the unsaturated bonds in the atoms.

However, a larger amount of LiOH and H2O was reacting because of their existing hydrophilic functional groups and the increase of surface atoms, which enhanced the composite’s heat storage performance. Moreover, LiOHH2O/CNSs’ heat storage density was higher as compared to that of LiOH.H2O/MWCNSs according to the TEM characterization results because of LiOH.H2O’s smaller size of the particle which existed in LiOHH2O/CNSs than that in LiOHH2O/MWCNTs (50–100 nm).

Contribution of nanoparticles

There are speculations that a greater contribution can be made by the smaller size nanoparticles to the improvement of TCMs heat storage density. As compared to the thermal conductivity of pure LiOHH2O, the thermal conductivity of these composed TCMs became higher after the addition of AC, MWCNTs, and CNSs to LiOHH2O. There has been no complete development of the manufacturing of LiOHH2O-based thermochemical materials, carbon nano additives-modified materials, and the inorganic hydrate’s heat storage density could be enhanced more by controlling its size of the particle and hydrophilic characteristic.

Conclusion

Lithium hydroxide monohydrate is an extremely unique and effective compound serving its purpose in different industries has gained a lot of recognition over the past years. Its applications and areas of applications have massively increased over time owing to the excellent characteristics and features that it brings forth. Different researches have been carried out in this regard, all of which make the efficiency and importance of lithium hydroxide monohydrate evident. All the application areas allow the compound itself and the industries to flourish in ways that bring consistency and efficiency in the growth of the market.

Synthesis and Application Areas of Cerium Oxide (CeO2)

Nanoparticles have been playing a major role in making lives easier for humans and strengthening the role of industries throughout the world.

Over the course of the past few years, nanoparticles have progressed so much that now they are being used in almost every field and are flourishing in it like anything.Cerium oxide nanoparticles are one of the rarest earth metal particles that are now being used for multiple purposes but excelling rapidly in the field of biomedical sciences. Their properties and characteristics make them unique and profoundly more amazing to work and utilize effectively.

Introduction

A significant role is played in nanotechnology by the nanomaterials in numerous scientific fields like materials sciences, chemistry, and physics. Nanoparticles are the major component of nanomaterials, and they are single species or particles. The diameter of the nanoparticles varies from 1-10 of the nanometers.

Significant efforts have been done over the recent years for the development of the various nanocrystals/nanoparticles to develop new exciting and remarkable applications in medicine, biology, cosmetics, environmental protection, transmission, optics, data storage, sensing, energy storage, and communications. Remarkable chemical and physical characteristics can be displayed by the nanocrystals such as their magnetic, electrical, and optical characteristics, because of their high density of edge or corner surface sites and limited size.

 

A rare-earth metal

In the periodic table, cerium is the lanthanide series’ first element and it is a rare earth metal. Cerium can exist in 2 states, 4+ and 3+ whereas most rare earth metals don’t have this ability. Therefore giving it an ability to exist in the bulk state as both Ce2O3 and CeO2. Cerium has exciting catalytic characteristics because 4d and 5p electrons shield the rare earth metal’s 4f orbitals sufficiently.

Cerium oxide at the nanoscale has a mix of cerium in the 4+ and 3+ states on the surface of the nanoparticle. The amount of 3+ sites increases on the surface as the diameter of the nanoparticle increases, therefore causing a loss of the atoms of oxygen (oxygen vacancies). The overall structure of CeO2−x depicts all this.

Sizes and ratios

High surface-to-volume ratios are possessed by the nanoparticles because of their lessened sizes, making them extremely reactive with distinct properties. Tuning the material’s characteristics in different ways like surface to volume ratios, morphologies, and shapes is extremely desirable. Huge efforts have been made by scientists and researchers over the past years for the development of nanoparticles with controlled size, shapes, and morphologies.

Gaseous, solid, and liquid (chemical method) media are some of the numerous potential routes of synthesizing nanocrystals. Although, the most famous methods are the chemical routes for manufacturing those nanoparticles that can provide the benefits like comparative reliability, eco-friendliness, and low cost. In addition, rigorous control can be provided by this method on the size- and shape-controlled manufacturing of the nanoparticles.

Advances in nanoparticles

Until now, there has been the development of nanoparticles of various nanomaterials, for instance, rare-earth oxides, ferrites, metal oxides, and so on. As compared to tin (60 ppm) and copper (66.5 ppm), the abundance of cerium is much higher. Cerium (Ce) is a rare-earth family metal. This material is very important from the technological point of view because of its high abundance, having a broad number of applications in different sectors like medicine, environmental chemistry, biotechnology, electrochromic thin-film application, glass-polishing materials, fuel cells, oxygen permeation membrane systems, oxygen sensors, low-temperature water-gas shift reaction, and auto-exhaust catalyst.

Non-stoichiometry levels

Generally, there is a belief that at high interface densities, the lessened particle sizes can originate, and thus it can also result in improved non‐stoichiometry levels. A huge amount of attention was given to them because of this for exploring the nanostructures’ ceria interfacial redox reactions and transport characteristics as compared to bulk ceria.

Electronic structure

Cerium has many oxides but the most stable oxide is considered to be Cerium dioxide (CeO2/ceria). In the lanthanide series of the periodic table, cerium is the most reactive element and the second member in that series. Ce4+ and Ce3+ are the dual oxidation modes in which cerium exists as it is electropositive in nature. As compared to 3+, the oxidation state Ce4+ is more stable because of the electronic structure [Xe]4f0 of Ce(4+) being more stable state as empty as compared to the electronic structure [Xe]4f1 of Ce3+. Usually, cerium sesquioxide (Ce2O3) and cerium dioxide (CeO2) are cerium’s two types of oxides. However, due to higher stability than cerium sesquioxide, cerium dioxide (CeO2) is utilized as the cerium oxide in the larger context.

Importance of oxygen vacancies in CeO2

High oxygen deficiency can be accommodated by cerium oxide through the substitution of the lower valent elements on the sub-lattice of the cation. High oxygen ion conductivities are expected because of this characteristic as it refers toward its possible usages in solid oxide fuel cells (SOFCs) as a solid electrolyte. CeO2 is famous right now for releasing oxygen in major levels at increased temperatures and low oxygen partial pressures (PO2), resulting in a mixed ionic electronic conductivity. Multiple states of oxidation like Ce (4+) and Ce (3+) can be easily occupied by ceria because of the ease in redox-based reactions, thus, electrons in ceria can exist as small polarons. In a ceria lattice, the motion of electrons can be a thermally mediated hopping mechanism. One should take into consideration the concentration of vacancies that can contribute to oxygen-ion transport in the solid solutions and are more mobile for transports and carrier characteristics.

Nano‐size effects

Production of more oxygen vacancies is displayed by ceria nanoparticles when the size of the particle is decreased. Cerium dioxide (CeO2) has a different reaction due to its remarkable characteristics because of the nanoparticle’s large surface area to volume ratio. For example, 3-CeO2 nanoparticles of 3-4 nm size were synthesized to support Au over a regular bulk cerium oxide support medium for observing two orders of magnitude high catalytic activity for oxidation of CO. Thus, tuning ceria nanoparticle’s specific reactivity is feasible by controlling the size of the ceria nanoparticles. In addition, in comparison with the bulk ceria, nano‐sized CeO2 has improved electronic conductivity, and size lattice relaxation along with various other effects.

Production of Cerium Oxide Nanoparticles

The preparation method determines the nanoparticle’s physicochemical characteristics. Parameters of preparation should be carefully optimized for selecting advantageous physicochemical characteristics in vivo for a bio-relevant nanoparticle. Cerium nanoparticles of different morphology, sizes, and agglomeration can result because of the different preparation methods. Generally, cerium nanoparticle’s lowered agglomeration can result in bio-relevant solution during a coating-post synthesis or synthesis by utilizing a surfactant or a polymer.

Formation of protein corona

While preparing the nanoparticle for usage in vivo, one of the main things to consider is the synthesis of a protein corona because the nanoparticle’s clearance and uptake are affected by protein corona. Lynch et al. reviewed the nanoparticle-protein corona and various readers read it.

Traditional Synthesis Methods

There have been reports on the various methods to synthesize CeNPs. Sol-gel methods, thermal hydrolysis, spray pyrolysis, thermal decomposition, ball milling, solvothermal, hydrothermal, and solution precipitation are included in these methods. Lower biocompatibility is faced by various traditional methods. Generally, lower toxicity, longer retention times, and greater stability are provided by the nanoparticle’s biocompatible coatings by lessening the non-specific interactions. Various coatings-polyacrylic acid, folic acid, glucose, cyclodextrin, polyethyleneimine, dextran, and polyethylene glycol (PEG) are used to functionalize CeNPs. Moreover, chelating MRI contrast agents like gadolinium can dope CeNPs for enhancing the safety of CeNPs while also demonstrating antioxidant characteristics.

Green Synthesis Methods

Bio-directed CeNP synthesis methods have attracted a lot of attention especially those that utilized natural matrices as stabilizing agents because they help in alleviating the bio-compatibility concerns. Safer routes are provided by these green chemistry methods to synthesize CeNPs and they are also very beneficial as they can be used in pharmaceutical applications. They also provide simpler alternatives and lower costs as compared to the traditional synthesis methods.

Also, the conclusion about their biocompatibility should be made only after they assess the formation of protein corona to manufacture CeNPs in biological fluid environments. There should also be an investigation on the usage of the methods of green chemistry to synthesize the CeNP’s biological characteristics and on the effect of Ce3+/Ce4+ surface ratio on those characteristics.

Strategies of green synthesis method

Nutrient-mediated synthesis, polymer-mediated synthesis, fungus-mediated synthesis, and plant-mediated synthesis are the main strategies that are involved in CeNPs’ green synthesis. Plant extracts function as capping and stabilizing agents in plant-mediated methods (photosynthesis). Plant-mediated methods (photosynthesis) lead to comparatively large CeNPs as the current ones are not good enough for applications in biomedicine.

Smaller CeNPs are produced to resolve mycosynthesis (fungus-mediated methods). Those CeNPs have high fluorescent, higher water dispersibility characteristics, and more stability. Natural polymers can function as stabilizers and helps in CeNPs’ green synthesis. For instance, PEG is utilized for creating dispersible nanopowders in aqueous solutions. The utilization of nutrient-mediated synthesis as a substrate is very cost-effective for synthesizing CeNPs. Egg white proteins function as stabilizers leading to small CeNPs controlled isotropic growth.

 

Bio-Relevant Activities of Cerium Oxide Nanoparticles

Enzyme Mimetic Activities

  • Degradation through catalase:

H2O2 is a potentially harmful oxidizing agent and catalase can degrade it. Higher catalase-mimetic activity is displayed by the CeNPs with low 3+/4+ ratios as compared to the CeNPs that have high 3+/4+ ratios. In order to read a brief overview of these activities’ mechanisms, readers can read the review that Celardo et al. wrote. CeNPs can be transformed into remarkable antioxidants if these activities are coordinated as both catalase-mimetic and SOD-mimetic activities are possessed by CeNPs.

  • Phosphatase Mimetic Activity

Phosphatases are enzymes. Phosphatases remove groups of phosphate from their substrate through esters’ hydrolysis into the phosphate ions. Phosphatase-mimetic capabilities are displayed by CeNPs with low 3+/4+ ratios for both bio-relevant substrates and artificial phosphate substrates just like it is for the catalase-mimetic activity. Although, recently it was exhibited that distinct active sites are possessed by the phosphatase-mimetic activity as compared to those for catalase-mimetic activity. Due to the abundance of phosphate anions in the biological solutions, it is very significant that one considers the interactions of CeNPs with phosphate anions for decreasing the SOD-mimetic activity while increasing the catalase-mimetic activity.

Evidence for Bio-Relevant Activities of Cerium Oxide Nanoparticles

Here, there are pieces of evidence of the antioxidant activities of the CeNPs by the reader. Each synthesis method that is utilized is listed in each synopsis and it is significant to the researchers that they remember these methods before using the same strategies in the new experiments. It is a request to readers to read Das et al.’s comprehensive review.

In Vitro Studies

CeNPs protective effects on primary human skin fibroblasts were displayed by Pezzini et al. especially those that were exposed to a pro-oxidative insult. Alfa Aesar gave the monodispersed CeNPs with 2 nm of the average diameter. After 1 and 3 days of incubation with CeNPs, fibroblast proliferation was assessed at 200, 100, and 0 µg/mL concentrations. CeNPs were internalized and they exhibited strong ROS scavenging activity and didn’t affect the fibroblasts viability. Moreover, mitochondrial function was affected by CeNPs by increasing the production of ATP, but it also preserved the potential of the membrane of mitochondria. This research is proof of CeNPs applications for a broad number of conditions.

Redox-active cerium oxide nanoparticles

Redox-active CeNPs are utilized for cancer therapy in combination with a therapeutic conventional, doxorubicin, according to Sack et al. observations. Karakoti et al. told that the CeNPs that this study used, were made specifically. Apoptosis, cell-cycle arrest, and DNA damage primarily mediate doxorubicin’s antitumor activity. Doxorubicin doesn’t only affect cancer cells, it also influences healthy cells. CeNPs’ antitumor activity with doxorubicin was compared by the authors and they established that in human melanoma cells (A375 cells), doxorubicin’s antitumor activity was enhanced by CeNPs, in the context of oxidative damage, ROS formation, and cytotoxicity.

Cytotoxic effects were exerted by both doxorubicin and CeNPs on the A375 cells and when CeNPs and doxorubicin are utilized together, A375 cell’s viability decreased more as compared to the decrease in its viability with each agent alone. In addition, doxorubicin’s toxic effects on human dermal fibroblasts (HDFs) were abolished by CeNPs.

Strategies in cancer therapy

Novel strategies are offered by such kinds of approaches in cancer therapy. CeNPs potential usages in brain tumor-related treatment have also been investigated by the same group. According to Sack-Zschauer et al., while CeNPs were protecting the healthy cells from damage, they also killed malignant glioma cells. 1.27 mg/mL of sodium polyacrylate was used to stabilize CeNPs which was bought from Sciventions. According to the authors, no cytotoxicity was displayed by CeNPs towards microvascular endothelial cells whereas they had a cytotoxic effect on anaplastic astrocytoma cells.

Nanoparticles in Medicine

Leukemia cells

It was established by Patel et al. that CeNPs’ uptake and free radical scavenging capability can be evaluated by human monocyte leukemia cells (THP-1 cells) which are utilized as a model. Hirst et al. described the synthesis of CeNPs by doing slight alterations to a basic method. In THP-1 cells, there was an increase in CeNPs’ internalization in a concentration-dependent manner between 10-100 µg/mL. Moreover, ROS amount was lessened by CeNPs without displaying any cytotoxicity. Therefore, instead of inducing the generation of ROS in the cytoplasm like any other oxide nanoparticles, the antioxidant activity was retained in the cytoplasm by CeNPs after quick internalization by THP-1 cells.

Cytotoxicity

High concentrations of CeNP were demonstrated by Sadhu et al. in tobacco BY-2 cells induce cytotoxicity and damage metabolic activity whereas antioxidant activity is exhibited when there are low concentrations of CeNPs. Sigma-Aldrich Chemical Co. gave the CeNPs that this study utilized, all of which were under 25 nm. For 24 hours, tobacco BY-2 cells were treated by authors with 250, 50, and 10 µg/mL of CeNP concentrations.

For higher concentrations of CeNP, major alterations and DNA damage in antioxidant defense systems were seen. Also, genotoxicity was not induced by CeNPs at 10 µg/mL of concentration and that resulted in lessened DNA breakage in the cells that were exposed to H2O2. These results indicate towards CeNPs’ alternative autophagy-mediated, gene-protective role, and antioxidant.

In Vivo Studies

Synthesis and design of triphenylphosphonium-conjugated CeNPs were reported by Kwon et al. as they localized to mitochondria and repressed the death of neurons in Alzheimer’s disease model. Hydrolytic sol-gel reactions were used to synthesize CeNPs. ROS’s abnormal levels can be caused by mitochondrial dysfunction and it can result in neuronal cell death subsequently. One of the great therapeutic approaches for neurodegenerative disease is targeting CeNPs to mitochondria.

Positively charged and small triphenylphosphonium-conjugated CeNPs were synthesized by the authors and they can localize mitochondria in numerous cell lines and can mitigate reactive gliosis while suppressing the death of the neurons. This can function as a great technique for developing mitochondrial therapeutics for neurodegenerative diseases like Alzheimer’s disease.

Tumor growth in ovarian cancer

According to the facts shown by Hijaz et al., the growth of tumors in an ovarian cancer xenograft nude model was majorly reduced by CeNPs. Das et al. and Cimini et al. used a synthesis strategy based on methods that were utilized for making folic acid-CeNPs and CeNPs. Intra-peritoneal injections were given to A2780 generated mouse xenografts as they were treated with 4 mg/kg cisplatinum, 0.1 mg/kg folic acid-CeNPs, and 0.1 mg/kg CeNPs. Lower tumor burden was carried by the mice who were treated with folic acid-CeNPs as compared to the mice who were treated only with the CeNPs. Tumor burden was further decreased when they combined cisplatinum with the folic acid-CeNPs. Moreover, vimentin expression was lessened by the folic acid-CeNPs, and that points towards a possible capability of limiting the ovarian tumor metastasis.

Retinitis pigmentosa

P23H-1 was used by Wong et al. for understanding the duration and cellular mechanisms of the catalytic activity of CeNPs to prevent photoreceptor cell loss. According to Karakoti et al., wet chemistry methods were used to prepare CeNPs. There was an observation of an increase in the post-injection function of cone and rod cells. Moreover, treatment by CeNP results in a lessening in the lipid peroxidation and apoptotic cells in the retinas. This research adds in the rodent retinal disease models list that exhibits a delay in the disease progression.

Obesity treatment

CeNPs’ antioxidant effects were investigated by Rocca et al. as an approach to treat obesity in the Wistar rats. CeNPs hindered the accumulation of triglyceride and caused an interference with the adipogenic pathway. Sigma gave CeNPs and their properties were the same as those that Ciofani et al. utilized in his famous study. At 0.5 mg/kg dose, CeNPs were intraperitoneally administered two times a week in 500 μL of sterile water for 6 weeks. After in vivo treatment, the transcriptional analysis took place and revealed an upregulation of Irs1 and Klf4 expression and a down-regulation of Ddit3,Angpt2,Twist1, Bmp2, and Lep. In conclusion, CeNPs reduced weight gain and lessened the plasma levels of triglycerides, glucose, leptin, and insulin.

Treatment of hepatic ischemia

Utilization of CeNPs in prophylactic treatment was investigated by Manne et al. and the investigation was done on Sprague Dawley rats and while treating hepatic ischemia-reperfusion injury in them. Median and left lateral lobes were induced with partial hepatic ischemia for 1 hour. Reperfusion for 6 hours followed it. On prophylactic treatment at 0.5 mg/kg with CeNPs result in a decrease in plasminogen activator inhibitor-1, myoglobin, human growth-regulated oncogene (GRO)/keratinocyte chemoattractant (KC), macrophage inflammatory protein-2, macrophage-derived chemokine, hepatocyte necrosis, lactate dehydrogenase, and alanine amino transaminase.

 

Conclusion

Cerium oxide nanoparticles have been progressing excessively in the field of biomedical sciences as they are being the major source of treatment of various deadly diseases. All of these applications are not only proved essential for humans but are being a major help in making the industries flourish all over the world. The researches conducted in this regard have been solid proof of the advancements and the establishments.

Applications of Graphene in Metal-Air Batteries.

Graphene being an allotrope of carbon possesses properties and characteristics that are extremely efficient and capable of setting a benchmark in various industries.

Though it is present in the form of tiny atoms combined, but when these atoms are combined, they hold a lot of strength as a result of which they are being produced at such a great rate and their applications as well have multiplied. Graphene is highly and cautiously being used in metal-air batteries as well because when graphene becomes a part of these batteries, their working mechanics expand, and ultimately their performance becomes outstanding owing to the excellent features and characteristics of graphene.

Introduction

Graphene is an arrangement of a 2-dimensional sheet of carbon atoms in a chicken-wire pattern. It is an extremely fascinating and attractive material. It possesses various exciting and remarkable characteristics like electrical and thermal conductivity, mechanical strength, intriguing optical characteristics, and more. Graphene’s comparatively high price is the only problem at the moment, other than that, it has already gained the attention of vigorous R&D.

 

Excellent structure

The structure of graphene is excellent whereas its discovery can seem easy and simple. A 2-D crystalline structure is possessed by graphene. The flat layer of atoms contains carbon’s hexagonal rings, giving graphene a structure like that of a ‘honeycomb’. 0.33 nanometers is the approximate thickness of the layer itself. Before graphene was discovered, no one believed in the existence of 2-dimensional molecules because of thermal instability.

Thinnest compound

A thickness of one atom, graphene is the thinnest compound that’s known, it is also the lightest material (0.77 milligrams is the approximate weight of 1 square meter). With 1 TPa-150,000,000 psi of Young Modulus and 130 GPa of tensile strength, graphene is the strongest compound that’s ever been discovered. As compared to steel, it is 100 to 300 times stronger. At room temperature, graphene is the best-known conductor of electricity and heat (at (4.84±0.44) × 10^3 to (5.30±0.48) × 10^3 Wm−1K−1). According to studies, graphene shows electron mobility at more than 200,000 cm2.v-1.s-1 of values. Graphene has other various notable characteristics, one of it is light’s uniform absorption across the spectrum’s near-infrared and visible parts (πα ≈ 2.3%), and it is also potentially suitable for being utilized in spin transport.

Carbon’s Abundance

One might find it astonishing that the human body has carbon as the second most abundant mass inside whereas by mass, this element is 4th most abundant in the universe, and it falls after hydrogen, helium, and oxygen. This is the reason carbon is the chemical basis for all life present on the Earth, which gives the graphene potential to be a sustainable, eco-friendly solution for approximately infinite applications. Applications in various scientific disciplines have increased since graphene has been discovered (the mechanical obtainment to be more accurate). Huge gains have been specifically made in energy generation and storage, ultra-wide bandwidth photodetectors, magnetic, chemical, and biosensors, and high-frequency electronics.

Graphene’s characteristics

Electronic characteristics

Graphene is a zero-overlap semimetal with extremely high electrical conductivity (with both electrons and holes as the charge carriers). This is another useful characteristic of graphene. 6 electrons in Total are possessed by the carbon atoms; in the outer shell, there are 4 electrons whereas, in the inner shell, there are 2. Pi (π) electrons are the name for these highly-mobile electrons and their location is below and above the graphene sheet. These pi (π) orbitals overlap and aid in improving graphene’s carbon to carbon bonds. These pi orbitals’ anti-bonding and bonding fundamentally dictate the graphene’s electronic characteristics (the conduction and valance bands).

Optical characteristics

Another interesting and exciting characteristic of graphene is its capability to absorb a large 2.3 percent of white light, particularly keeping in mind that its thickness is only 1 atom. It is because of the electronic characteristics of graphene that the electrons function like massless charge carriers with extremely high mobility. It was proved some years ago that the Fine Structure Constant determines the amount of white light that is absorbed, instead of being dictated by the material specifics.

Mechanical characteristics

The inherent strength of graphene is one of its other characteristics that stands out. Other than being remarkably strong, graphene is extremely light too at 0.77milligrams per square meter (to compare, a paper’s square meter is roughly a thousand times heavier). There’s a famous saying that goes around that graphene’s single sheet (of the thickness of only 1 atom), is enough in size for covering a complete total field but its weight wouldn’t be more than 1 single gram itself.

What are the current usages for Graphene?

Graphene possesses numerous applications and the reason for that is the characteristics of graphene. The market has been introduced with many graphene products since 15 years of it being isolated for the first time, and every year, graphene expands into new areas.

Graphene-based electrodes for the flexible multivalent metal-ion batteries

Multivalent metal’s low cost and abundance are the main reason for the success of flexible multivalent metal-ion batteries like Al and Zn-ion. A huge amount of attractions has been gained by the zinc-ion batteries (ZIBs) specifically with their easiness to scale up, high safety, and benefits of two-electron redox. In ZIBs, the dominant cathode material is the NaV3O8∙1.5H2O (NVO) but because of NVO’s poor conductivity, its theoretical capacity (486 mAh g−1) has been way more as compared to its reported capacity. The vacuum filtration method was used by Wan et al in introducing NVO on the highly conductive graphene and he attained rGO/NVO composite film with remarkable flexibility. At 100 mA g−1, 410 mAh g−1 of high capacity was delivered by the graphene-based composite films and even under various bending states, flexible ZIBs’ discharge curves stayed stable.

Graphene-based electrodes for the flexible Li-air batteries

A flexible GO paper was utilized for the first time by Cetinkaya et al. for the Li-air batteries as the cathode. Enough porosity for O2 diffusion was provided by the vacuum-filtered GO paper, therefore enhancing the efficiency of Li2O2’s decomposition and formation. After 10 cycles of it being used for the Li-air battery as the cathode, 612 mAh g−1 of discharge capacity and 585 mAh g−1 of charge capacity were delivered by it. Although, the device’s life cycle and capacity didn’t reach the demand for practical usage because of the GO paper’s poor conductivity. Conductive graphene nanoplatelets (GNPs) were introduced by Kang’s group into GO for the preparation of the flexible GNP/GO films by using the vacuum-assisted filtration method. Disordered and highly wrinkled morphology was displayed by the attained paper-like film.

 

Graphene-based electrodes for the flexible metal-air batteries

Recently, a huge amount of attention has been gained by the metal-air batteries specifically in the zinc-air and lithium-air because of the comparatively high energy density. It is important to fabricate flexible electrodes for attaining the flexible metal-air batteries. The flexible air cathode’s search is way urgent as the thin metal foil (zinc or lithium foil) can be utilized for the flexible metal-air battery as the anode and it displays a particular degree of flexibility. Remarkable air permeability should be possessed by the cathode as the metal-air batteries’ efficient operations depend on the oxygen-evolution reaction (OER) and oxygen-reduction reaction (ORR). Although, the specific capacity decreases because various flexible substrates possess poor electrochemical catalytic activities and low porosity.

Rate performances

Divalent cations’ slow diffusion in the cathode is unfortunately still the reason for most ZIBs’ unsatisfactory rate performance. A graphene-based flexible ZIB was made by the Fan’s group for attaining high-rate ZIBs. They grew novel layered zinc orthovanadate (ZOV) on the flexible graphene form and it functioned as the cathode. Also, they utilized the porous graphene foam for supporting Zn array mode. Remarkable flexibility and mechanical stability were consequently shown by both the graphene-based anode and cathode, where after the repeated bending, no active materials were seen being peeled off from the graphene substrate. Long cycle life (2000 cycles) and 50C of ultrahigh rate performance (discharge in 60 seconds) was delivered by the attained flexible Zn-ion battery.

Electrical conductivity

In addition, it displayed flexibility and 164 S cm-1 of good electrical conductivity, therefore enabling it for being utilized directly as a freestanding cathode without utilizing any binders and conducting additives. At 100 mA g−1 of current density, 9760 mAh g−1 of high full discharge capacity was delivered by the final device because of the advantages of high surface area and good conductivity.

Alternatively, the electrochemical performance could be enhanced further by the introduction of catalysts towards OER and ORR. A CeO2-graphene foam flexible composite was developed by Jiang et al. for the Li-air batteries. Here, hydrothermal treatment was done for growing CeO2 microspheres on the 3D graphene foam. Good flexibility was displayed by the graphene-based composite cathode and it could be folded easily. Rapid O2 diffusion occurred because of the porous framework and improved catalytic activity was displayed by the CeO2 toward ORR because of the contributions of the porous framework. Flexible Li-air batteries can steadily cycle for 80 times after folding up to 1000 times because of the advantages from these merits.

Graphene-based electrodes for the flexible sodium-ion batteries

Developing their alternatives is still important because of the limited lithium resources while the commercialization of LIBs has been completed. Due to the sodium resources being cheap and broadly available, an extensive amount of interest has been gained by sodium-ion batteries (SIBs).

Graphene-based electrodes for the flexible Zn-air batteries

In comparison with the flexible lithium-air batteries, the flexible Zn-air batteries are more attractive because of their merits of environmental friendliness and abundant resources. Just like lithium-air batteries’ cathodes, excellent ORR/OER electrocatalytic activity, high electrical conductivity, air permeability, and remarkable flexibility should be possessed by the cathodes of zinc-air batteries. Due to risks of electrolyte leakage and evaporation, utilization of flexible zinc-air batteries is significantly limited by using fluidic liquid electrolytes. It is because of their inherent reliability and safety that the flexible all-solid-state Zn-air batteries are superior to flexible electronic devices.

Usage of pure graphene films

Pure graphene films can be naturally utilized for SIBs as flexible electrodes. A facile filtration method with a subsequent annealing treatment was used by Song’s group for developing a porous graphene film and defects and extra edges were produced in the graphene film by using ferric nitrate for offering more electrochemically active sites for high capacity. As a result, when it is utilized as the SIBs anode, a high capacity of 111 mAh g-1 was delivered by the porous graphene film when it is utilized as the SIBs anode even after 1000 cycles at 1000 mA g−1.

Doping of heteroatoms

Alternatively, the electrochemical characteristics of graphene films can also be enhanced by doping the heteroatoms into the graphene films. Thiourea was first dissolved into GO’s aqueous dispersion by Deng et al. to develop a sulfur-doped flexible graphene film and a gelation process was subsequently initiated. At 100 mA g−1, 377 mAh g-1 of high capacity is possessed by the sulfur-doped graphene film, way higher as compared to the capacity of the pristine graphene film which at 100 mA g−1 is around 100 mAh g−1. Other than a single element doped graphene, enhanced electrochemical performance was displayed by the co-doped graphene with the binary elements. A solvothermal process was done by An et al. to make N and F co-doped graphene paper.

Nitrogen-doped nanosheets

They grew the atomically thin layer-by-layer mesoporous Co3O4 on the nitrogen-doped rGO (N-rGO) nanosheets as the bifunctional catalyst and high activity was displayed by the composite because of the strong synergistic effect between N-rGO and atomically thin Co3O4 and large surface area. A zinc wire was used as an anode, gel polymer as an electrolyte, and CoOx/N-rGO composite as an air cathode, to fabricate a fiber-shaped all-solid-state zinc-air battery. 36.1 mWh cm−3 of high volumetric energy density was also displayed by it. Under numerous types of extreme deformations like knotting, and bending, the achieved flexible Zn-air battery can perform stably, and they are integrated into the clothes for powering numerous electronic devices. They knitted 3 fiber-shaped zinc-air batteries sets (3 in-series zinc-air batteries are contained by each set) in a cloth and that could be enough to charge the iPhone 4S.

Recent advancements in flexible batteries

There has been a review of the recent advancements in the graphene-based electrodes for numerous flexible batteries, like metal-air batteries (Zn-air, Li batteries), lithium-sulfur batteries, and metal-ion batteries (K, Na, Li-ion batteries). Graphene-based electrodes function in these devices as a flexible substrate for supporting electrochemically active materials of nanorods, nanospheres, and amorphous nanoparticles, where they will guarantee the flexible batteries’ high capacity and enhance the active material’s conductivity. Moreover, good enough space is provided by the porous graphene structures for accommodating the active material’s over expansion, therefore achieving good cyclic stability.

 

Applications of metal-air batteries

Using Metal air battery for the treatment of heavy metals in the water

Arsenic is strongly toxic and is a heavy metal. Normally, in nature, it is in pentavalent and trivalent form. Serious damage will be caused to the human body if the drinking water (>0,01 mg/L) contains arsenic in excessive amounts. Thus, effective removal of excess arsenic from the water is extremely significant. Currently, arsenic-removing methods include sedimentation method, coagulation, biological treatment method, membrane separation method, absorption method, etc. Some of the above methods are expensive, some need longer processing time, and some need related processing facilities. Treatment of arsenic in water by using a metal-air battery device is a novel method. Electricity is simultaneously produced by this reaction and it can’t remove arsenic effectively from the wastewater. Utilizing a metal-air battery device to process gives good processing results and needs only simple equipment too.

Utilization of the Metal air battery for collecting substances in water

In water, coagulants or electrolysis is added to collect some substances for forming precipitation, and then separate those substances from the water. Not only do these methods enhance the quality of the water, but they also obtain the goal of utilizing particular substances again. This method also completes the demands of sustainable development of environmental and economic protection. Some researchers tried utilizing the metal-air battery for collecting the substances in the water. In water, an element that is commonly found is phosphorus. If the standard is exceeded by the content, it will result in a series of problems like water’s eutrophication.

Phosphorus and magnesium salt’s combination

Struvite (MgNH4PO4) can be formed by combining excessive phosphorus with the magnesium salt in water, and struvite is then collected. A magnesium-air battery was made with air cathode and magnesium anode by Dae Hwan Lim et al., and he utilized the phosphorus-containing wastewater as a battery electrolyte for the collection of phosphorus in the water. According to the study, when there is a low concentration of phosphorus in the water, NaCl’s addition in the electrolyte can have a higher collection efficiency too. Also, a passivation layer made up of struvite is produced on the magnesium anode’s surface when there is a gradual increase in the concentration of the phosphorus, leading to a decrease in the magnesium anode’s dissolution rate. Magnesium anode’s low dissolution rate is the reason for the reduced phosphorus collection rate.

Enhancement in performance

After NaCl’s addition to the electrolyte, the phosphorus collection efficiency and battery’s power generation performance are all enhanced with the NaCl dosage’s increase, which is mostly because of the magnesium anode’s surface passivation layer being destroyed by Cl-. Although, a passivation layer is produced on the magnesium anode’s surface when the concentration of phosphorus in the water is extremely high (more than 0.05 mol/L), further greatly reducing the collection efficiency. The addition of Cl- will no longer enhance the magnesium anode’s surface condition. Thus, it uses a magnesium-air battery at an appropriate concentration of phosphorus for the collecting struvite.

Treatment of production and domestic wastewater by the metal-air battery

High ammonia nitrogen, high chroma, high COD, and other characteristics are possessed by aquaculture wastewater. Serious pollution problems will be caused if the wastewater is discharged directly into the water. In China, there is a wide distribution of the aquaculture industry into numerous rural areas. In most villages, the treatment facilities are not good enough. Various aquaculture wastewaters are discharged without treatment in the water, resulting in local water’s serious pollution. Currently, metal-air batteries have been utilized by some people for studying the aquaculture wastewater’s treatment effect, and some of the results have been obtained.

 

Iron air battery’ and aluminum-air battery’s construction

Swine wastewater was treated by Zhao et al. by making an iron-air battery and aluminum-air battery. They studied swine wastewater’s electricity production performance and treatment effect by setting different metal anode, different pH values, and different conductivity (adding NaCl’s various concentrations can adjust this). According to the findings of the study, the electrical performance of the battery will be better if the conductivity is higher. Different values of pH influence the discharge of the device, but it’s a slow impact. They also used a bimetal electrode to create an air battery while exploring the conventional influencing factors. The best performance was made by the battery with a double metal anode configuration. In the experiment, there was a study on the bimetallic anode’s metal-air battery. According to the findings, the best performance was of the battery with aluminum-iron double anode. The experimental device subsequently treats the swine wastewater.

Utilization of two methods

They utilized two methods. In one method, wastewater was added as an electrolyte into the experimental device for treatment purposes. In the other method, the solution is added to the device into the wastewater for the treatment as a coagulant.

Conclusion

Metal air batteries are extremely beneficial for today’s world as they are serving various purposes in industries and human lives as well. However, the incorporation of graphene in these batteries has massively increased their production and applications, most of which are said to be found in the area of treatment of water. This is due to the combined excellent features of graphene and metal-air batteries.

How nanotechnology can benefit smart cities

Nanotechnology is the indulgence of nanomaterials that are extremely tiny and are unable to be seen with a naked eye and rather a microscope is needed to see them. They are measured in nanoscale owing to their tiny nature.

However, their size does not define their characteristics because they are rich in so many good features which not only make lives easier but also play a huge role in improving the economy. Cities are on their way to becoming smart cities and a lot of cities are already called smart cities and this has only happened due to the use of nanotechnology in cities which has massively brought positive changes and improved the lifestyle of people. There are several ways in which nanotechnology plays a role for smart cities, all of which are briefly explained in this article.

Introduction

“Nanoscience” aids us in understanding how nature works when it is seen on a tiny scale, the famous ‘nanoscale’, for instance when objects of the size of some nanometres are observed and their characteristics are studied. Moreover, a nanometre is a minuscule length’s unit: 1 nanometre is equal to 0.000000001 meters, 0.000001 mm, or 0.001 microns or micrometers. You can use scientific notation like: 1 nm = 10-3 microns = 10-6 mm = 10-9 m, for writing the same chain of equivalences. The prefix ‘nano’ (tiny) is used for referring to the things that are extremely, small.

 

Information about nanotechnology

Nanotechnology is more than nanoscience and its purpose is converting the basic knowledge that it gives us, regarding the goods and material’s new characteristics, to propose radically new ones or for the enhancement of the existing products. Essentially nanotechnology is concerned with how the knowledge that is coming from the nanoscience is being applied. Large investments are needed by the knowledge generation and they can have an advantageous return if such knowledge gets practiced. The fundamental application of knowledge generation occurs at research centers and universities, whereas the development of the knowledge application should occur in technological companies or centers.

Research about nanotechnology

It is usually felt that nanotechnology and nanoscience are almost futuristic and modern terms that one sees in Television series, novels, movies, and comics. Although, their innovations are not that much as its been nearly 50 years since the research in nanoscience has been brewing in the research laboratories. Richard Feynman, who won the Nobel Prize in Physics in 1959, anticipated various tools and concepts that are being utilized right now in this fascinating discipline. Although, it’s been 15-20 years since the last dramatic boost from companies, institutions, and governments has been seen by nanotechnology and nanoscience, because they now know its huge potential.

Nanotechnology’s influence

The media and society have been highly influenced by “nanotechnology”. In this article, it will be utilized for referring to both the basic and the applied aspects. The nanoscale is a country that many kinds of nanostructures and nanoobjects inhabit. It is also known as the “nanoworld”. Viruses, ribosomes, proteins, DNA strands, semiconductors and metal nanowires, graphene, carbon nanotubes, nanoparticles, molecules, atoms, etc. are included among those nanostructures and nanoobjects that inhabit it. Nanofauna displays various phenomena which would not exhibit themselves in their present as it has way great size, all of this makes nanofauna interesting. That’s why nano is said to be different as it adds a significant value to everything as compared to the macro or micro.

Characteristics

Although it’s not only the surface’s significance as the objects go smaller and smaller, they also display the other mechanisms that can only be explained by the intriguing quantum mechanics. Scientists wrote the “manual of laws and rules” for understanding the laws, rules, and nature, and that’s the way to understand quantum mechanics and explain the formation of complex molecules and various other more objects. It also explains the reaction of those complex objects towards light or magnetic fields, electric fields, and mechanical deformations. It’s not alarming as this exciting discipline’s basics won’t have to be studied by the participants of the I+D+I Research Program.

Quantum effects

Those nano-objects in a series of “quantum” effects should be known which result in the presence of exciting characteristics. For instance, the electrons that are moving in a nanoparticle have allowed energy levels. The allowed energy levels are the certain energies that the moving electrons possess because of the quantum effects. Moreover, the allowable values for these energies start to change as the nano objects start becoming smaller. That’s why when you change the object’s size, various optical, magnetic, or electrical characteristics that are determined by these energy levels are changed too.

Advancements thanks to nanotechnology

Nanotechnology has aided us in innovating at the super microscopic nanoscale for forming materials that were unavailable previously and are extremely durable, conductive, and flexible. We can obtain incredible improvements in industry, science, and every field of our life by using these tiny nano-particles or instruments.

How will the future of smart cities be affected by Nanotechnology?

Following the latest enhancements in science and society, it is assumed that in the future, smart cities are gonna expand for accommodating various processes and larger populations within the cities and various processes will turn increasingly automated. Currently, nanotechnology is already affecting various areas in city life and there are clear pieces of evidence that this usage and impact of nanotechnology will only rise in the coming years.

Enhancement of existing cities

It is certain that with the ongoing advancements happening in the entire world, almost all the cities as well as trying to incorporate new technology but most of these methods include correcting the already present models and infrastructure. The already built models are being worked upon to add up or increase their value of them. The smart cities of the future will be needing and having an entire change of technology besides enhancing the already present models. This includes the use of nanotechnology to a great extent as it is playing such a huge role in this matter.

Smart Cities

All the cities are now thriving to become smart cities however, if we start calling it smart living then it would be more appropriate. Most cities are already incorporating new technologies in their daily lives to enhance their quality of life. These include the internet of things, huge databases, and algorithm related to machine learning all of which play a major role in enhancing the present infrastructure and also move a step towards the technology upgrade.

Revolution of industrial processes

There has to be a proper system through which various variations can take place and that is where all the smart networks combine after which the data is integrated and moved into the 4th industrial revolution. The thing is that the systems on which the cities are depending are capable of revolutionizing a lot of industrial processes, this is why these are being run continuously for better commercialization and understanding of how and why certain technologies shall be given an upgrade. The areas of maintenance are being approved at a greater level too because they add up to the enhancement of infrastructure as well.

Advanced monitoring

There are certainly other factors and aspects as well which are a major part of smart cities and include rather much more advanced forms of monitoring that usually take place in terms of the health of buildings structurally and an effective network of traffic that goes around cities. These factors are used to promote the protection of cities in terms of economy and environment, however, the most important factor that affects smart cities is the use of sensors. Sensors are necessary in terms of localizing the data points and then the transmission occurs over long distances as well all through the help of the internet.

Millimeter-wave technology

For the effective transformation of data by using 5G, NASA engineers were the ones who opted for the development of nano-enabled millimeter wave technology. This enables the effective transmission of data via the radio airwaves and prevents our cities from any disturbance or disruption. Before this, even the thought of digging up to a new fiber cable every few years for the carrying out of the same process seemed to be an unsustainable idea. However, nanotechnology enables this entire process by making the use of millimeter-wave technology effective through the building of a virtual fiber network as it successfully transfers unlimited data without any disruption. This works as a successful step towards the development of smart cities as this is the faster and most effective way of data transmission.

Incorporation of engineering and software

It is clear that incorporation of engineering and software that enable all the ongoing processes of smart cities, ‘smart’ but it is important to have an accuracy of data. Sensors play a vital role in manufacturing smart cities and these are the main objects that possess nanomaterials. The software programs that are carried out in this regard require so many different parts which work together in cohesion and besides that nanotechnology is playing a role in making the cities smart without encompassing any major changes to the previously enabled infrastructures.

Graphene Nano-Enabled Highways and Skyways

Graphene is capable of enabling highways and skyways which are stretched to a one-kilometer range of roads possibly present in Rome, Italy. This has been possible due to Directa Plus and Ilterchimica. Graphene comprises of such properties and characteristics which enable it to work in different sectors and usage of it as an additive in the road is one of those sectors. The resistance to wear of roads is possibly improved through the introduction of a tiny amount of graphene into the asphalt. Ultimately, through this, the life of roads increases from 6 to 12 years and becomes able to fight any adverse climate changes. This is how important nanotechnology is in moving towards the establishment of smart cities and enhancing the quality of living for all the people around.

Flexible buildings

The nanomaterials are also being used for the formation of flexible buildings which play a resistive role against polluted and dangerous environments, this also includes the intake of CO2 in the atmosphere. Nanotechnology is working tirelessly to bring ease for the people living in cities and that is why the structural course of buildings is also being enabled. This will add up more flexibility to the buildings and they can be kept safe and protected from any environmental hazards including earthquakes etc. Due to a good life in cities, more people are moving towards cities so it is evident that in future nanomaterials will be used more excessively in creating rather a much better living in cities and ultimately transforming them into smart cities with smarter future.

 

Nano-Enabled Smart Healthcare

Healthcare is considered the backbone of any smart city so keeping it maintained is very much necessary. It is surely going through a phase of transformation as nanomedicine is paving its way towards a future that can be extremely beneficial for future generations as well. Nanomedicine is taking care of so many processes that are going on in the healthcare systems, including refrigeration processes and point of care treatments specifically to build up a larger infrastructure. Nanotechnology is highly beneficial in combating life-threatening diseases so that a better and healthier future for our upcoming generations can be promoted.

Common diseases

Nanomedicines are being used to fight a lot of hazardous diseases including MS, Alzheimer’s, and Parkinson’s. However, these can be protected via injecting twice a year as nanomedicine carries along with such kind of potential. Another major beneficial aspect is that such medical assistance can be provided to everyone without having to consider the affordability issue.

Applications of Graphene in Medicine

Nanomedicine is also rapidly bringing a change in healthcare with a lot of new uses in terms of drug delivery systems, therapies, vaccinations, diagnostics, etc. The introduction of telesurgery and telemedicine is also being brought to the front desk so that these advancements can bring a positive and healthier change in smart cities.

Pandemics and plagues

It is also very prestigious that the pandemics and plagues can be controlled and looked upon via the use of Nanosensors including nanomedicines and general care diagnostics. Advancements have been made to such an extent that there are certain tools and technologies which have been discovered to fight Ebola and the Zika viruses. Nonetheless, nanotechnology has helped in preventing the world from a pandemic by managing all the possible harms and mutations that these viruses can cause and spread.

Nano-Enabled Infrastructure

When an urban area expands, construction becomes an integral part of the entire growth process specifically in terms of infrastructure. The components that are used as building materials are extremely necessary and need to be vigilantly checked as they are the key role players of a competent building. Concrete and cement have already been used with the nanomaterials and further usage alongside nanomaterials is adding quality to the buildings which become functional for longer periods and not only strengthen the infrastructure but also provide it with the desired quality. Maintenance of heat and cold inside buildings can also be looked at which the nanosensors are capable of identifying and exhibiting.

Safety and security

Safety and security along with fancy and upgraded outputs are very much necessary. A city can become a smart city only if it is provided with high safety and security. The Chinese are working in using and developing nano latex inks for the signs present on roads to look after the traffic movements. Ultimately, all of this also affects the entire environment and works as regards a safer environment.

Nanotechnology in eco-paints

Adding up to all the uses of nanotechnology for smart cities, eco paints have also come forward as nanomaterials are now being used in eco paints as well. These paints are capable of performing two functions, one is as an anti-corrosive coating and the other one is the absorptive solution which is responsible for the catalysis of air pollutants to green gases. Eco paints are largely responsible for eradicating pollution from the cities and rather being called environment friendly.

Nano-Enabled Energy and Water resources

Energy and water resources are also being used with the help of nanomaterials and are bringing and upgrading the quality of smart cities. Batteries having the most potential are now gaining the attention that they deserve with the potential use of nanomaterials as a part of them. However, a lot of work in this regard is still being carried out to bring forth the safety and efficiency that is necessary for the smooth running of smart cities. Electric vehicles are competent enough to bring forth quality changes in smart cities that is why the production and usage of electric vehicles have massively increased as well. In this way, energy storage mediums have also gained a lot of attention and usage.

Nanotechnology in water purification

Energy storage mediums

Everyday electronics including stoves, washing machines, blenders, juicers, irons, etc are considered as the energy storage mediums and these have also started the use of nanomaterials in them. The major concern is safety when it comes to energy storage mediums so a trail test is run before launching them in the market where when these energy storage mediums containing nanomaterials are utilized for several years without causing any certain harm then they are a perfect fit for the smart cities. Their quality speaks for itself when no damage is caused to either the consumer or the product itself. Nanomaterials are, however, very famous for going through the testing trials as they are launched in the market only when they pass through that test.

 

Nano-Enabled Food

Food packaging is highly beneficial for the proper storage and protection of food that is why nanomaterials in food packaging had been introduced and they have not failed once. However, researches are being gone on to incorporate nanotechnology in foodstuffs as well. The conclusion is still being awaited though. Meeting the safety standards is a crucial process and can take longer periods but once the target is achieved, success seems fruitful. The flavor, texture, and color of foodstuffs are specifically being worked upon as these are the key things necessary for a food item to grow in the market.

Reduction of salt and sugar in food

Excessive use of salt and sugar cause so many diseases which can be highly dangerous to human life that is why nanotechnology has stepped in and is now being used to limit the amount of salt and sugar in the food industry specifically in Europe as it is mainly responsible for the growth of nano-enabled meat and fish. This impacts the food industry in a very positive manner and allows prioritizing health when it comes to consuming carbohydrates and calories. This is not only a healthier step towards the food industry but also towards a healthier and positive environment.

 

Nano-Enabled Smart Living

Digital media is one of the most common concepts in today’s era and is playing a key role for our future generations in terms of technology. However, nanotechnology is playing its role in this regard as well because it enables the storage of data that becomes helpful in providing education to people. The unique features and characteristics of nanomaterials are enabling them to be utilized in our homes and anything that we are certainly using for daily life achievements. This has brought a lot of stability to the daily lives of people and has moved another step towards the maintenance of smart cities.

Conclusion

Nanotechnology by far is being used in almost every other field owing to the excellent characteristics and features that it comprises. In today’s world probably all the cities are transitioning to smart cities as nanotechnology is helping speed up the process. Upgrading the entire technology is surely a hard process but when achieved it does bring so many positive changes because it enhances the quality and quantity of life.

Explained: Graphene, Graphene Oxide, and Reduced Graphene Oxide and Applications

Graphene is a very interesting material. It is a 2-dimensional sheet that is formed of carbon atoms. Graphene has certain characteristics as at 0.77 mg/square meter, it is very light and strong. Although graphene is a semi-metal substance, yet it possesses high electrical conductivity. It also absorbs white light up to 2.3%. Graphite oxide can be turned into reduce graphite oxide. The quality of reduced oxide is less than graphene. Artificial graphite oxide can be formed by treating graphite with a strong oxidizer.

Offerman and Hummers are the methods that are used to produce graphite oxide. The chemical properties of graphene oxide and graphite oxide are almost the same but their structures are very different. The two most used methods for the conversion of graphite into graphene are utilizing stirring and signification.

Introduction

In the past scientists have applied different methods for the creation of GO from rGOrGO has been used in composite materials, energy storage, and field-effect transistor. GO and rGO have been used in gas sensing applications. Because of the high conductivity, rGO has gained much attention and due to good sensing abilities GO has gained attention. Because of high electrical conductivity, cyclic stability and specific surface area rGO is a nice option for super capacitance. GO and rGO possess anti-bacterial characteristics. GO also has biomedical applications.

 

Graphene oxide

Graphene oxide is graphene’s form. Oxygen functional groups are included in it, and it has remarkable characteristics that can differ from the characteristics of graphene. These oxidized functional groups are eliminated by lessening graphene oxide for attaining a graphene material. Reduced graphene oxide is the name of this graphene material, it is usually referred to as rGO. Graphite oxide can also give rGO. It is a material that is made of a combination of many graphene oxide layers, after reduction’s series to graphene oxide and rGO.

Graphene’s Characteristics

Mechanical characteristics

The inherent strength of graphene is one of its other excellent properties. At 0.77 milligrams per square meter, graphene is extremely light and extraordinarily strong. Paper’s 1 square meter is 100 times higher, roughly. Usually, it is said that graphene’s single sheet of one atom thickness, is enough in size for covering a complete football field, while weighing under 1 single gram.

Electronic characteristics

One of graphene’s most beneficial characteristics is that it’s a semimetal with zero-overlap (with both electrons and holes as charge carriers) with extremely high electrical conductivity. 6 electrons in total are possessed by the carbon atoms, 4 are contained in the outer shell and the inner shell contains 2. Pi (π) electrons are the highly-mobile electrons. The location of the Pi electrons is below and above the graphene sheets, and they overlap. The overlapping of these pi orbitals aid in improving graphene’s carbon to carbon bonds. The anti-bonding (the conduction and valence bands) and the bonding of these pi-orbitals fundamentally dictate graphene’s electronic characteristics.

Optical properties

It is an interesting and rare property of graphene that it has the capability of absorbing a large 2.3% white light, particularly taking into consideration that its thickness is only 1 atom. This property of graphene is because of its already mentioned electronic characteristics; the electrons function like massless charge carriers with extremely high mobility. It was proved some years back that the Fine Structure Constant determines the amount of white light that’s absorbed, instead of being dictated by the material specifics.

How is rGO formed?

Graphene oxide’s (graphite oxide) reduction to rGO is attractive and famous as the cheap and effective ways of making graphene (rGO) are being intensively sought. There is an existence of various methods of reduction, and they are simple and cost-efficient.

Defects

rGo has the same characteristics as graphene and it is graphene’s form (good conductive characteristics etc.). Usually, more defects are contained by rGO and it is of lower quality as compared to graphene that is made from graphene directly. Residual oxygen and other heteroatoms along with structural defects are contained by the reduced graphene oxide (rGO). rGO is considered an interesting material that is enough for numerous applications in quality, but more attractive manufacturing processes and pricing. However, rGO is still considered to have a less than perfect resemblance with pristine graphene. One can use reduced graphene oxide for the same numerous applications that are appropriate for the usage of graphene, for instance, sensors, conductive inks, and composite materials. It all depends on the quality of the specific material.

Natural choice

It is them having ease in producing enough graphene’s quantities at a comparatively low cost that makes the reduced graphene oxide an understandable and natural choice for applications calling for the material’s large amounts. The process of making reduced graphene oxide is very significant as a large influence is made by it on the produced-rGO’s quality, and thus will determine the range of closeness rGO will come to pristine graphene, regarding characteristics and structure.

Number of processes

GO can be reduced and there are various processes to do that, based on electrochemical, thermal, or chemical approaches. High-quality rGO like high-quality graphene can be produced by using some of these methods but carrying them out can be time-consuming, expensive, or complex. There are various approaches to functionalizing the material in various applications for particular usages once the production of reduced graphene oxide is completed. We can improve the compound’s characteristics for suiting commercial applications by combining rGO with other 2-D materials to create new compounds or by treating rGO with numerous chemicals. GO’s a reduction to rGO is performed in some applications as a device manufacturing process’s part.

Example

For instance, GO can start a process, if it is mixed with material for creating a composite, and lessen GO as a part of the composite creation process or afterward into rGO.

Graphite Oxide

It is a compound that contains oxygen, hydrogen, and carbon molecules. Graphite is treated with strong oxidizers like sulphuric acid for the artificial creation of graphite oxide. These oxidizers react with the graphite and eliminate an electron in the chemical reaction. Such kind of reaction can also be called a redox reaction, as the reactant is oxidized and the oxidizing agent is reduced.

Hummers and Offerman method

In the past, the Hummers and Offerman methods have been the most usual method to create graphite oxide. In this method, a mixture of potassium permanganate (an extremely strong oxidizer), sodium nitrate, and sulphuric acid, for treating graphite. Although recently there has been a development of the other methods that are more efficient according to the reports, passing 70% of the oxidization levels, via utilization of increased amount of potassium permanganate, and instead of adding sodium nitrate, it involves the addition of the phosphoric acid combined with the sulphuric acid.

Oxidization

The oxidation has graphene oxide as its by-product as when graphite reacts with the oxidizing agent m, the interlayer spacing between graphite’s layers is increased. Then the oxidized compound can disperse in a base solution like water, and produce graphene oxide.

Difference between graphene oxide and graphite oxide

There are a lot of chemical similarities between graphene oxide and graphite oxide but they are extremely different when it comes to structuring. Water intercalation between the compound’s atomic layers due to water intercalation causes the interplanar spacing between the compound’s atomic layers and that is the major difference between the graphene oxide and graphite oxide. The oxidation process causes this increased spacing and it disrupts the sp2 bonding network too, which shows that both graphene oxide and graphite oxide are usually known as electrical insulators.

Graphite Oxide to Graphene Oxide

Individual graphene layers can be extremely damaged from the process in which graphite oxide is turned into graphene oxide, and when further lessening the compound, it has more consequences. More damages are undesirable as the Individual graphene platelets are already damaged by graphite’s oxidization process to graphite oxide, thereby lessening their mean size. Flakes of a few layers and monolayer graphene are contained by the Graphene oxide, interspersed with water (depending on the base media, surface functionality can weaken the platelet to platelet interactions, resulting in enhanced hydrophilicity).

Possible methods for the conversion

There are some possible methods for turning graphite oxide into graphene oxide. Utilizing stirring, sonication, or both’s combinations are the most usual methods. An extremely time-efficient way to exfoliate graphite oxide is sonication, and its success rate in exfoliating graphene is extremely high (almost too full exfoliation levels), but graphene flakes can also be heavily damaged by it, lessening them in surface to nanometres from microns, and also forms a broad range of graphene platelet sizes. Mechanical stirring can take a lot of time for accomplishing and it is a much less heavy-handed method.

From Graphene Oxide to Reduced Graphene Oxide

Producing reduced graphene oxide by reducing graphene oxide is a very major and critical process as it possesses a large influence on the produced-rGO’s quality, and this will determine the closeness that rGO will come to pristine graphene, regarding structure. rGO is the clearest solution in large-scale operations too because it has comparatively eased in forming graphene’s enough quantities.

Numerous reduction ways

The reduction can be attained in a different number of ways, although all of them are methods that are based on electrochemical, thermal, or chemical means. Extremely high-quality rGO like pristine graphene can be produced by using some of these techniques, but carrying them out can be time-consuming or complex

Scientists have made GO from rGO in the past by

  • Using hydrazine hydrate to treat GO and maintaining the solution for 24 hours at 100.
  • Exposure of GO for some seconds to the hydrogen plasma
  • Exposure of GO to strong pulse light’s another form, like those that the xenon flash tubes make.
  • Heating the GO at various degrees in distilled water for various lengths of time.
  • Linear sweep voltammetry
  • Combining GO with an expansion-reduction agent like urea and then a solution will be heated for the area for the release of reducing gases, after cooling.
  • Heating GO directly in the furnace to extremely high levels.

Structure

GO is also used by the rechargeable batteries in their structure. GO material’s high specific surface area is essential for these materials’ high capacity like rGO. In addition, active bonding areas are offered by the oxygen-containing compounds on the surface of GO for electrochemical materials. It is because of the production of solid electrolyte interphase (SEI) and Lithium ions reaction with the oxygen functional groups that give GO-based anodes its poor cycling capacity even though changing the concentrations of the oxygen-containing compounds can tune the GO’s electrical characteristics. GO has been successfully utilized in the cathode materials however it exhibited poor performance in Li-ion batteries anode materials. For instance, the GO/LiFeSO4F composite functions as a cathode material for enhanced rate capability and cycle stability for LiBs.

rGO Applications

It can be generally said that rGO can do what graphene does because the characteristics of both of these materials are very much alike, however at the rGO end, albeit is less impressive. Specific rGO’s chemistry and resulting morphology along with the preparation method determine the rGO’s characteristics. One can use the reduced rGO for various applications and among those applications are field-effect transistors, composite materials, energy storage, and more.

Energy Storage

rGO is used for energy storage applications in lithium-oxygen, lithium-sulfur, and lithium-ion batteries. This material’s high surface area is a significant benefit for attaining high-capacity energy storage devices. These rGO materials extremely conductive nature are especially used in the rechargeable batteries’ cathode and anode materials. The exchange of electrons and effective ion transfer is promoted by the conductive carbon network.

Rate capability

Moreover, the rate capability can be enhanced by the Li’s high diffusivity on the graphene planes. For instance, rGO platelets were decorated by Fe2O3 nanoparticles and were utilized for lithium-ion batteries as an anode material that displayed 1693 and 1227 mAh g-1 of discharge and charge capacities. rGO electrode was under various studies and they exhibited that when it comes to high capacity energy storage applications, rGO is a convenient material.

Cathode material

In lithium-ion batteries, free-standing rGO films are successfully utilized as the cathode material. High-capacity cathode electrodes require a high content of functional oxygen-containing compounds in the structure of rGO.

Lithium-sulfur batteries

In lithium-sulfur batteries, GO composites are used to develop high-energy density batteries. For instance, lithium and sulfur polysulfide’s can use reactive functional groups 9’ the GO materials to immobilize themselves on the GO materials. Lithium-sulfur cells are enabled by the strong interaction between sulfur and GO or polysaccharides. They displayed stable cycling for more than 50 deep cycles and 950–1400 mAh g-1 of high reversible capacity.

Solar Cells

rGO and GO’s large specific surface area is important and exciting characteristics for solar cells applications. GO is used in organic photovoltaics as an effective interfacial layer (IFL) and is also utilized as the hole transport and electron blocking layer because of its semiconducting characteristics. Under environmental and thermal stress, GO majorly improves the durability of the device by increasing the active layer-IFL interfacial stability.

Cathode materials

GO is additionally used in dye-sensitized solar cells’ cathode materials in combination with rGO composite’s counter electrodes like multiwall carbon nanotube-rGO nanoribbon and rGO–TaON composite.

Sensors

There has been the utilization of both rGO and GO in gas sensing applications. Due to their high electrical conductivity and surface area, rGO gains attention whereas due to its high and active surface area, GO displays good sensing capabilities. rGO/CuFe2O4 nanocomposite is used for a high–performance NH3 gas sensor which utilizes CuFe2O4 sensing ability and rGO’s conductivity. On the other hand, cuprous oxide and graphene oxide (GO/Cu2O) nanocomposite-based sensors are utilized for trimethylamine (TMA) gas sensing. Good stability, selectivity, reversibility, and sensitivity are shown by the system in 60 days. Both GO and rGO nanocomposites are good sensors for humidity, nitrogen dioxide, and hydrogen.

Supercapacitors

Supercapacitors function based on electrochemical double-layer capacitance (EDLC) and release energy -5 the electrochemical interface by nanoscopic charge separation between an electrolyte and an electrode. rGO is a good option for the Supercapacitors applications of a new generation because of rGO’s cyclic stability, specific surface area, and high electrical conductivity.

Super capacitor electrodes

Supercapacitors electrodes are developed by using several different rGO nanocomposites like rGO/ZnO, rGO-carbon black, and rGO/Zn/PCz. These Supercapacitors have enhanced the capacitance to up to 33.80 F/g, leading to high energy (E= 1.66 Wh/kg) and power- (P = 442.5 W/kg) storage capabilities. Additionally, reduced graphene oxide further increases the surface area and Supercapacitors capacitance consequently and it is utilized for Supercapacitors applications in the form of aerogel. Although, the studies on GO are less because of the GO material’s lower electrical conductivity as compared to rGO.

Membranes

Graphene oxide’s porous structure and chemically active nature can be used to enhance the characteristics of the membrane and the separation performance. People used GO-polymer composites for CO2/N2 and O2/N2 separation applications. Furthermore, the membrane’s mechanical characteristics can enhance by including GO into the structure of the membrane.

Biosensors

GO and rGO’s composites are utilized as field-effect transistors (FET), electrochemical, and optical biosensors. Usually, metal nanoparticles like silver or polymers and platinum are contained by these composites. Biocompatible rGO and GO have been exploited in a broad range to sense biomolecules like arbitrary DNA mutation, optical aptamer, multiplexed microRNA, DNA/RNA aptamer, microRNA, D-glucosamine, DNA, and glucose.

Optical biosensing

GO material’s fluorescent behavior is utilized for the applications of optical biosensing for detecting various biological molecules like metal ions, food toxins, NAs, dopamine, H2O2, and cancer biomarkers glucose.

Biomedical Applications

Remarkable biocompatibility and DNA adsorption characteristics are shown by GO. According to findings, the binding of DNA to GO is extremely reversible and stable. Characteristics like these make the preparation of DNA-based graphene materials easy and possible for numerous bio-applications. Drug delivery particularly, the huge amount of attention is gained by the GO-based materials. High cellular uptake and extremely low cytotoxicity are shown by GO Nano sheets, as they did some explorations on these suitable nanocarriers for intracellular fluorescent nanoprobe and drug delivery. Various graphene-based composites were used for efficient drug delivery by using polymer grafting, for instance, patterned substrates of Nano-GO, fluorescent GO, functionalized GO nanoparticles, hyaluronic acid-decorated GO nanohybrids, and GO/hydrogel-based angiogenic.

Diagnostic and photo-thermal therapy

Other than the applications in drug delivery, GO-based materials are utilized for photo thermal therapy and diagnostic applications too. Alzheimer’s disease is also diagnosed by using fluorogenic resveratrol-confined GO and hybrid GO-based plasmonic-magnetic multifunctional nanoplatforms. GO and gold nanostars were used in combination in therapeutic applications for ultra-efficient and effective photo thermal cancer therapy. Great potentials are possessed by rGO in photo thermal therapy against heat-induced controlled drug release and cancer due to their excellent photo thermal effect.

Antibacterial characteristics

Promising antibacterial characteristics with a wide antibacterial spectrum are shown by both GO and rGO finally because of their excellent antibacterial mechanism and remarkable physicochemical characteristics. These structures’ antibacterial activity is enhanced by using metals like gold and silver often as nanocomposites materials with rGO and GO. ZnO/GO composites of ZnO’s varying contents in high quality and excellent antibacterial characteristics are possessed by these composites against Escherichia Coli with low cytotoxicity. Dental pathogens are killed by using the GO-based material’s antibacterial characteristics.

Conclusion

Graphene is an enthralling substance with unique optical, electrical, and thermal properties, as well as mechanical strength and other properties. Graphene is a two-dimensional sheet of carbon atoms arranged in a chicken-wire pattern. Graphene is the center of intense R&D, but its relatively expensive price is a barrier for the time being

​Mesocarbon Microbeads (MCMB) Graphite Micron Powder for Lithium-Ion Battery

Lithium is a very important element of the periodic table and it has a very effective manner in the field of science and all the fields related to it. It is one of the most renowned and beneficial products of lithium and so is of the lithium-ion batteries. They are most certainly used for electronics of all sorts but most commonly for portable electronics. They come with great characteristics and properties and it is because of them that they are highly profitable in the market.

For the Li-ion batteryMesocarbon Microbeads (MCMB) Graphite Micron Powder is one of the most efficient ways to utilize the li-ion batteries as it brings authenticity to the batteries and their working and functioning.

Introduction

One of the rechargeable battery types is a Li-ion battery or lithium-ion battery. Mainly, the Li-ion batteries are utilized for electric vehicles and portable electronics, they are being developed for applications in aerospace and military. A Li-ion battery prototype was made in 1985 by Akira Yoshino. Earlier, during the 1970-80s, many researchers researched it, and then in 1991, a commercial Li-ion battery was made. The development of the Li-ion battery made Yoshino, Goodenough, and Whittingham get a Nobel Prize in Chemistry in 2019.

When the battery is charging, the lithium ions flow to the negative electrode from the positive electrode through an electrolyte and return when discharging.

 

Li-ion batteries usage

At the negative electrode, graphite is the typically used material, whereas, at the positive electrode, the material is an intercalated lithium compound. Low-self discharge, no memory effect, and a high density of energy are possessed by the batteries. However, due to containing the flammable electrolytes, they can be a danger and can result in fires and explosions if not charged correctly or damaged.

After the fires caused by Lithium-ion, Samsung had to recall the Galaxy Note 7 handsets. In addition, various incidents have taken place, involving batteries on the Boeing 787s.

Different Li-ion battery types have different chemical properties, different safety, cost, and performance. Lithium polymer batteries are mostly used in handheld electronics. As an electrolyte, the polymer gel is used. As the cathode material, lithium cobalt oxide (LiCoO2) is used, providing high energy density, but also displaying risks to safety, and more when they are damaged. Meanwhile, lithium nickel manganese cobalt oxide (NMC or LiNiMnCoO2), lithium manganese oxide (LMO, Li2MnO3, or LiMn2O4), and lithium iron phosphate (LiFePO4) provide lower energy density, although it offers less risk to safety and proved longer lives. These batteries are used broadly for medical equipment, electric tools, and other roles, whereas, the derivatives of NMC and NMC itself are used broadly in electric vehicles.

Some of the areas of research for Li-ion batteries are increased speed of charging, lessening cost, enhancing safety, increasing energy density, lengthening the lifetime, and some others. The electrolytes that are non-flammable are being researched as if they can be a lead factor in improving the safety based on the organic solvent’s volatility and flammability which are used in an electrolyte. Heavily fluoridated systems, ionic liquids, polymer electrolytes, ceramic solid electrolytes, and aqueous Li-ion batteries are included in the strategies.

Typically, Li-ion battery life is the number of complete cycles of discharging and charging in order to get a failure threshold in terms of impedance rise or capacity loss. The word ‘cycle life’ is used typically for specifying the lifespan as the number of cycles for reaching the battery’s 80% capacity. The capacity of the batteries is also lessened by their Inactive storage. For representing the complete battery life cycle, the Calendar life is used, involving both the inactive storage operations and the cycle.

Lithium-ion Battery Applications

Li-ion batteries usages

Different devices are provided with high energy density, lightweight power sources by Lithium-ion batteries. For powering devices as large as electric cars, instead of connecting with one large battery, the more efficient and effective way is connecting various small batteries in a parallel circuit.

Such devices include:

Power tools: in tools like saws, sanders, cordless drills, and different equipment of garden, for instance, hedge trimmers and whipper-snippers, the lithium-ion batteries are used.

Portable devices: Devices like flashlights (torches), game consoles that are handheld, electronic cigarettes, camcorders, digital cameras, tablets, laptops, smartphones, and mobile phones are included.

Electric vehicles: The batteries of electric vehicles are utilized in advanced electric wheelchairs, personal transporters, electric bicycles, scooters, cars, and motorcycles, and hybrid vehicles. The Li-ion batteries are utilized in applications of telecommunication. Reliable backup power is provided by the secondary non-aqueous lithium batteries for loading the equipment in a telecommunication service provider’s network environment.

At locations like huts, Electronic Equipment Enclosures (EEEs), and Controlled Environmental Vaults (CEVs), lithium-ion batteries are suggested for deployment. The users of Lithium-ion batteries need brief, dangerous material information specific to the battery, appropriate procedures of fire-fighting, for meeting the regulatory requirements, and for protecting the surrounding environment’s equipment and employees.

 

Properties

In the periodic table, the first of the alkali is Lithium. Li7 and Li6 are the mixtures of isotopes that are found in nature. Having a low and reactive melting point, it’s whitish-silver, soft, and the lightest solid metal possible. As compared to its own group ones, most of its chemical and physical characteristics are more same as the alkaline earth metal’s characteristics. Lithium’s remarkable properties are its extremely low density, low viscosity, high thermic conductivity, in state of liquid there’s a huge temperature interval, and its high specific heat (calorific capacity). The metallic lithium in hydrocarbons is insoluble meanwhile in the short-chain aliphatic amines, for instance, etilamine, it is insoluble.

Lithium reacts a-lot with both, the inorganic and organic reactants, on a huge scale. Peroxide and monoxide are formed on its reaction with oxygen. For the formation of black nitrure, it is the only alkaline metal that reacts at ambient temperature with nitrogen. Lithium hydride is formed on the reaction of lithium with hydrogen at 500ºC (930ºF). The reaction of the metallic lithium with water is very vigorous. Carbure is produced by the direct reaction of lithium with carbon. With very light emission, it produces halogenures on binding with the halogens easily. Even if it can’t react with the parafinic hydrocarbons, it reacts a lot with alquenes which the diene and ariele groups substitute. Significant for the synthesis of vitamin A, lithium acetylures, can be formed on lithium’s reaction with acetylenic compounds.

Mesocarbon Microbeads (MCMB) Graphite Micron Powder for the Li-Ion Battery

Heat and Residua of petroleum derive Mesocarbon microbeads (MCMB), it’s then treated under various conditions of the experiment, characterized by electron diffraction and X-ray, Fourier transformed infrared spectroscopy (FTIR), electron paramagnetic resonance (EPR), and proton magnetic resonance (PMR). Under vacuum, after heating to 750 C, the presence of the hydrogen’s two different forms is retained. Graphite ribbon-like particles are formed by graphitization to 3000 C, surrounding microbeads of a size of few microns.

The EPR observed that the crystalline graphite monodomains are either semi-metallic or having a small bandgap. Even at 3000 C temperature, the heat treatment doesn’t totally eliminate the microbeads’ localized paramagnetic defects. These characteristics condition these material’s aptitude towards their usage in sodium and lithium electrochemical cells. At 750 C, the samples that are made have a reversible intercalation behavior, whereas, the samples that are made at 3000 C, evidence solvent decomposition leading to a non-reversible lengthened discharge plateau when using the sodium perchlorate electrolyte which is completely dissolved in propylene carbonate.

For the Li-ion cell’s negative electrode, the usage of the intercalation compounds that are based on carbon, makes the concern of the present state expanded to various allotropes and different carbon’s artificial and natural forms. From the structural respective, the carbons that are related to graphite can be classified as unorganized carbon, graphitized solid, and turbostratic material. There are different capacities for intercalation of lithium into each one of these forms. Depending on the graphite’s transforming facility, the forms that are less organized can be classified into the hard and soft carbons, and above 2000 C into the graphitic carbon, meanwhile the latter doesn’t display graphitization’s characteristic signs, even heat-treated at 2800 C. Soft carbons are mostly cokes, and also mesocarbon microbeads (MCMB). Other than being the first commercial Li-ion cell’s part, the soft graphitizable carbon’s most broadly used form is the petroleum coke.

In comparison to the usage of other graphitizable fora to use as an active material, the usage of coke for the intercalation electrode’s performance is typically limited.

MCBC has specifically shown promising behavior. This material contains a low specific surface area, and structures that are roughly spherical (microbeads) and has a diameter of 1–40 mm. During Li-ion cells’ charge/discharge process, there are additional side reactions with the electrolyte which can be avoided by the high packing density.

Recently, a huge amount of attention has been gained by the Li-ion batteries because of their superior characteristics, for instance, the long life of cycle, high energy densities, and environment-friendly nature. For products of electricity, for instance, laptops and phones, Li-ion batteries are significant.

In lithium-ion batteries, carbon materials are generally used as anode materials because of their small surface change, structural stability during cycling, and high energy density.

One of the carbon materials that is used as a material for the anode in Li-ion batteries is mesocarbon microbeads. For Li-ion batteries, the mesocarbon microbeads (MCMB) Graphite Micron Powder are a special kind of carbonaceous materials. Mesocarbon microbeads generally have spherical shapes with a diameter of 1-50 µm and when mesocarbon microbeads are used as anode materials in lithium-ion batteries, they can provide a reversible capacity of 300-340mAh/g and excellent cyclability which is a big advantage for the applications where high capacity is needed.

Another advantage of mesocarbon microbeads is that they can be in combination with silicon to have higher capacities and rechargeability. It is a fact that mesocarbon microbeads anode materials have the best cyclability among all the types of carbon anode materials. When we combine mesocarbon microbeads with silicon to obtain an anode material, we can obtain Silicon – mesocarbon microbeads composite material with high capacity and satisfactory rechargeability. So it is possible to extend the number of charging cycles of lithium-ion batteries by using silicon – mesocarbon microbeads composite anode material.

Conclusion

Mesocarbon Microbeads (MCMB) Graphite Micron Powder for Lithium-Ion Battery is a very renewed way of making the lithium-ion batteries beneficial and useful in their respective field of science. They are excessively used in portable electronics and are paving a new way to success for the electronics and for the consumers of those very electronics. The working mechanisms to broaden their essentiality are in continuous progress.

​Lithium Carbonate in Lithium-Ion Battery Applications

Lithium-ion batteries are known as those rechargeable batteries where lithium ions work through transmitting from the negative to the positive electrode. These are one of the most used batteries in today’s world as they are being used for so many different purposes owing to the excellent features that they bring forth. Lithium carbonate is a white salt that works as an inorganic compound with a mixture of lithium, carbon, and oxygen.

Lithium-ion batteries become much more powerful and active with the incorporation of lithium carbonate in them as it enhances the production and applications of these batteries. 

Introduction

A Li-ion battery or lithium-ion battery is a rechargeable battery type in which the lithium ions move through an electrolyte during discharge and charge, from the negative electrode to the positive electrode. Graphite is typically used at the negative electrode by the Li-ion batteries and an intercalated lithium compound is used as the material at the positive electrode by the Lithium-ion batteries.

 

High energy density

Low self-discharge, no memory effect (except LFP cells), and high energy density are possessed by the Li-ion batteries. The manufacturing of cells is done for either prioritizing power density or energy. Although, they can be a hazard as flammable electrolytes are possessed by them and they can result in fires and explosions if charged incorrectly or damaged.

Development of Lithium-ion battery

In 1985, Akira Yoshino made aprototype Lithium-ion battery, based on the research that was done earlier during the 1970s-1980s by Koichi Mizushima, Rachid Yazami, M. Stanley Whittingham, and John Goodenough, and then in 1991, Yoshio Nishi led the team of Asahi Kasei and Sony and developed a commercial lithium-ion battery. Li-ion batteries are getting famous for aerospace and military applications. They are utilized commonly for electric vehicles and portable electronics.

Characteristics

Different types of Li-ion batteries have different safety characteristics, cost, performance, and chemistry. A graphite anode, a lithium cobalt oxide (LiCoO2) cathode material, and lithium polymer batteries (with polymer gel as electrolyte), are mostly used by handheld electronics, which combined provide a high energy density. Better rate capability and longer lives are offered by lithium nickel manganese cobalt oxide (NMC or LiNiMnCoO2), lithium manganese oxide (LMR-NMC, LiMn2O4 spinel, or Li2MnO3-based lithium-rich layered materials), and lithium iron phosphate (LiFePO4). Such batteries are utilized broadly for medical equipment, electric tools, and other roles. There is a wide usage of NMC and its derivatives in electric vehicles.

More areas of research for lithium-ion batteries

Increased speed of charging, lessening cost, enhancing safety, increasing energy density, and extended lifetime, among others, are the areas of research for lithium-ion batteries. There has been research in progress in the area of the non-flammable electrolyte as a method for increasing safety based on the organic solvent’s volatility and flammability that are utilized in a normal electrolyte. Methods include heavily fluorinated systems, ionic liquids, polymer electrolytes, ceramic solid electrolytes, and aqueous lithium-ion batteries.

 

Present Day Li-Ion Batteries

As compared to the real small electronic devices for the 3C market that is mentioned above, the current lithium-ion batteries market is way more complicated. Various markets have been started for small devices like medical devices, vaporizers, e-cigarettes, lighting (fluorescent lights and LCD), and toys. The discovery that the Li-ion battery packs utilizing 26650, 26700, and 18650 sizes can be made for functioning at way higher power as compared to what was originally suspected, has opened markets for e-bikes, garden tools, portable electric tools, and various other products.

High energy cells

Some capacity has already been sacrificed by some of the high power cells for achieving 20A or more continuous discharge capability in the cell size of 18650, whereas now 3.4 Ah or more is possessed by high energy 18650 cells. Sustaining a high capacity during cycling is difficult even though some cells have as high as the capacity of 2.5 Ah. Spotnitz, Reimers, and coworkers did modeling studies that clearly showed the significant effect of tab placement and multiple tabs. Carbon type that is utilized in the negative electrode, electrode’s porosities, positive electrode’s carbon content, and thickness of the electrode are other major design variables.

Development of ceramic coatings

Moreover, it is because of the metal particle’s adventitious presence on the electrode’s surface that the production of ceramic coatings to the positive electrode or the separator has had an advantageous effect on the prevention of internal short-circuiting while cycling. Generally, these particles are airborne and small and they usually result from the electrode’s mechanical slitting. The separator’s thickness is only 12-25 μm. This thickness proves that the concept of extremely small conductive particles penetrating the separator, causing a short, is a significant failure mechanism of the Li-ion batteries. Such separator coatings can be as thin as the thickness of 2 micrometers. They can be on one or both of the sides of the polyolefin separator.

Additional benefits

Separator’s coating has other additional benefits, which include enhanced electrolyte wetting due to the easily wet inorganic oxide ceramic phase, better cycling if, during cycling, a weak short circuit degrades capacity without making any safety incident, and separator’s much-lessened shrinkage at the shutdown temperatures (current’s shutdown because the melting of the separator may not succeed if the shrinking reaches to an extent that the direct contact between the cathode and anode is permitted). Now, more difficult coatings are turning common, for instance, Panasonic and Tesla motors used the Sumitomo separator which involves coating with aromatic polyamide (aramid polymer) and also ceramic particles for increasing the coating’s strength of penetration.

Present cathode materials

LiMn2O4 (LMO) and the original LiCoO2 (LCO) are included in the cathode materials that are in common usage currently. LiNixMnyCo1-x-yO2 is another excellent material that’s still under development. Generally, It is known as NMC. Usually, the subscripts are known by their atomic ratios like 811, 442, or 532 (other than the x = y = 1/3 which was investigated initially and known as 111 or 333). 532 and 111 are the most usually utilized materials.

Competitive materials

Moreover, LiNi0.80Co0.15Al0.05 (NCA) is an extremely competitive material, also a layered R3-m structure. Several groups competitively made a more recent material, known as LiFePO4 (LFP) with a 1-dimensional tunnel structure. Each material has some particular disadvantages and advantages and they have been implemented in various applications.

Lithium carbonate

With Li₂CO₃ formula, the lithium salt of carbonate, it is an inorganic compound. It is utilized in a broad range as a drug to treat numerous mood disorders and in processing metal oxides.

Reactions and Characteristics

The existence of lithium carbonate takes place only in the anhydrous form, unlike sodium carbonate, which produces 3 hydrates at least. As compared to the other lithium salts, it has low solubility in water. Lithium’s isolation from lithium ores’ aqueous extracts capitalizes on this poor solubility in water. Under carbon dioxide’s mild pressure, there comes a 10-fold increase in its apparent solubility. This effect is because the production of the metastable bicarbonate and metastable bicarbonate is more soluble.

Li2CO3 + CO2 + H2O ⇌ 2 LiHCO3

Extraction of lithium carbonate

Quebec process’s basis is lithium carbonate’s extraction at CO2’s high pressures and its precipitation on depressurizing. The exploitation of lithium carbonate’s diminished solubility in hot water can purify lithium carbonate. Therefore, Li2CO3’s crystallization can be caused by heating the saturated aqueous solution. Group 1’s lithium carbonate and other carbonates do not readily decarboxylate. The decomposition of Li2CO3 occurs at 1300 degrees Celsius of temperatures.

Lithium carbonate’s usages

Lithium carbonate is a significant industrial chemical. The main usage for lithium carbonate is as a precursor in the Li-ion batteries. There are plenty of usages of the glass produced from lithium carbonate in the ovenware. In both high-fire and low-fire ceramic glaze, the ingredient that’s commonly used is lithium carbonate. Lithium carbonate produces low-melting fluxes with other materials and silica. Its alkaline characteristics are conductive for altering the metal oxide colorants state in glaze, red iron oxide (Fe2O3) specifically. When they are made with lithium carbonate, cement is set more fastly, and cement is beneficial for the tile adhesives. It produces LiF when added to the aluminumtrifluoride, and it gave a superior electrolyte to process aluminum.

Rechargeable batteries

Lithium carbonate’s main usage is as a precursor to the lithium compounds that are utilized in the Li-ion batteries. Practically, lithium compounds are used to make two components of the battery; the electrolyte and the cathode. One of the various lithiated structures are used by the cathode, lithium iron phosphate and lithium cobalt oxide are among the most popular, whereas the electrolyte is lithium hexafluorophosphate’s solution. Before being converted into the compounds that are mentioned above, lithium carbonate may convert first into lithium hydroxide.

Lithium Carbonate in Li-Ion Battery Applications

Li2CO3 production from the concentrated lithium brine

They took concentrated lithium brine in trucks to 232 km for refinement and processing from Salar de Atacama to Antofagasta, Chile. A payload of 24.5 tonnes is carried by each truck. Boron is eliminated from brine at the Li2CO3 production plant and then goes through purification and carbonation according to Steinbild and Wietelmann.

Boron extraction facility

An organic solvent, sulfuric acid (H2SO4), alcohol, and hydrogen chloride (HCl) are consumed by the boron extraction facility. At the extraction phase, lime (CaO) and soda ash (Na2CO3) is added to the treated lithium brine for removing magnesium. Li2CO3 is yielded as a solid by a precipitation reaction for which soda ash is combined with purified brine. Before its compaction and packaging, the end product is dried after being washed and filtered.

Material’s total consumption

Total water, energy, and material used for producing Li2CO3 were determined by using the producer data. As there is no need for the process-level analysis and a single product —Li2CO3— is produced by this facility that’s why the whole process of production of Li2CO3 is treated at the facility level. Particulate matter emissions data were provided other than energy inputs, water, and material for the operation of the facility. Energy and material flow for the production of Li2CO3 from lithium brine. Water isn’t included in the LCL as despite being utilized in the process, it is not consumed and is a completely recycled stream.

Stages of lithium carbonate

LiOH•H2O is formed by the reaction of Li2CO3 in a series of stages with a mixture of water and CaO. There is still no need for process-level analysis as only LiOH•H2O is the product from the facility. At the facility level, data was analyzed and the material inputs and requisite energy were determined for the production of LiOH•H2O. There are 2 facilities for the production of LiOH•H2O and Li2CO3 at the same plant respectively but there is a separation of the facilities and there is unique data for the production of each.

Requirement of production

During the process of refining, auxiliary chemicals are required by the production of Li2CO3. CaO, organic solvent, alcohol, HCl, H2SO4, and soda ash are included in these, and they all are modeled in GREET. These resources’ default amounts of production and transportation are utilized in this analysis with an anticipated Chilean production basis. CaO is the exception, as its production is done in the US, and trucks and ships are used to transport it to Chile, with a distance of 200 and 5000 miles (322 and 8047 km). The utilization of this CaO proxy was for anonymization.

Various allocation approaches

In China, the stage of carbonate production is extremely energy expensive. As compared to the 4 Chilean allocation methods, it performs worse. Also, a meaningful influence is possessed by Na2CO3 input on energy usage. It should be noted that the transit stage is for the analyzed product’s transit only. Here, Li2CO3 is the analyzed product. As compared to the brine-based pathway, the ore-based pathway functions worse.

Lithium carbonate’s concentration

The primary driver of GHG emissions for the brine-based pathways is Na2CO3 followed by the energy for the production of concentrated brine (determined by brine allocation approach) and Li2CO3. After spodumene concentrate, the main driver for the ore-based lithium is Li2CO3 production. Production of Li2CO3’s production in China is modeled on a facility which is utilizing coal for heat, and then transitioning it to natural gas which would most probably lessen the GHG emissions.

GHG emissions

The findings for Li2CO3’s brine-based formation are in consistency with the literature, whereas there are different GHG emission findings for the Li2CO3 that’s produced from the ore. According to Dunn et al.’s old work that was turned into GREET model, GHG emissions of 3.8 tonnes of CO2e per tonne of Li2CO3 from brine. According to Kendall and Ambrose, Li2CO3 that’s produced from brine leads to Li2CO3 of 3.06 tonnes of CO2e per tonne.

Differentiation in production

The production of Li2CO3’s synthesis from brine is different from the synthesis of Li2CO3 from ore. According to the findings of Ambrose and Kendall, ore-synthesized Li2CO3 makes 2.28 tonnes of CO2e per Li2CO3 of a tonne. New information is reflected in this study, identifying increases in carbon dioxide per tonne of Li2CO3, in the usage of Na2CO3, and in energy inputs for the formation of Li2CO3 itself.

Effect on battery system

We can see lithium production’s impact on the whole battery system. NMC811 and NMC622 cathode materials were examined to be used in the automotive battery. 241 Wh/kg is the NMC622 battery’s specific energy based on Argonne’s BatPac Model, whereas it’s 248 Wh/kg for an NMC811 battery. The 300-mile range is achieved by both the batteries as they have an energy capacity of 84 kWh. 54 kg LiOH•H2O per battery kWh (0.09 kg Li per battery kWh) is contained by an NMC811 battery, whereas 0.57 kg Li2CO3 per battery kWh (0.11 kg Li per battery kWh) is contained by an NMC622 battery.

Inputs of battery materials

Argonne BatPac Model v4.0 was used to model the battery material inputs for both NMC811 AND NMC622 (Argonne National Laboratory 2020). In 2020, these batteries’ life cycle inventory details are described by Winjobi et al. for GREET integration. Here, those material’s battery bills and details of energy usage are used along with the brief lithium production processes that were mentioned earlier for evaluating the impact that the various lithium sources have on the batteries’ life cycle (and allocation approaches). Again, GREET’s baseline settings are used for gathering the background data.

Connections in terms of lithium’s production

LCA was overall utilized for connecting lithium’s formation from ore or brine via formation of NMC811 and NMC622 cathode powder, formation of lithium compounds (LiOH•H2O and Li2CO3), and resource concentration, all the way through the utilization of lithium in NMC811 or NMC622 battery’s form, in an electric vehicle. According to the analysis, the reported environmental effect is impacted by the resource allocation approach that’s used and the lithium source matters (ore or brine) with respect to environmental effects. Those process-level LCA results are recommended by us as this analysis was capable of leveraging the process-level data for production based on the brine. They are recommended as they are most representative of water utilization, materials, and actual process energy in the formation of concentrated lithium brine.

Lithium Carbonate’s recovery

Sieving can easily separate the Al foil in the residue after the leaching of the formic acid. ICP-OES can be used to analyze each element’s mass fraction in the Al foil where 99.98% is Al’s mass fraction. The above-mentioned procedures were done to process the leach solution for carrying out the leftover Mn, Co, and Ni. Excessive (110%) saturated Na2CO3 is added to subsequently obtain lithium carbonate for achieving lithium carbonate. In water, Lithium carbonate is slightly soluble, and as the temperature increases, the solubility decreases.

XRD pattern

The achieved lithium carbonate’s XRD pattern agrees with the standard pattern peaks. Aqua regia further dissolved the precipitated Li2CO3 for calculating lithium carbonate’s purity accurately, and ICP-OES was used to measure its mass fraction of metals.

Lithium carbonate’s SEM images

The precipitated Li2CO3’s SEM images show that the precipitated Li2CO3 was displayed as severe agglomerates of various primary sheets. According to findings, 10.64 ± 1.47 μm is the particle size distribution. After precipitation, 98.20% was Na+ mass fraction in the solution among the metallic ions, where HCOO— is the anion through the complete process of leaching. Then the solution can be processed further for the preparation of NaCOOH or utilized directly after the adjustment of pH for processing of leather, and the Ni-Co-Mn precipitates are ready for cathode materials’ precursor formation.

Developing New Lithium-Ion Battery Production Process

There was schematic plotting of a new Li-ion battery formation process under formic acid’s leaching on previous experimental and theoretical result’s basis. All the metals have global recovery rates of over 90 percent. Mainly, the cathode scrap’s Mn, Co, and Ni were recovered in the residue solution with little loss as hydroxide precipitates (Ni−Co−Mn precipitates I and II). Around 0.005 wt percent of Ni-Co-Mn was lost as Al foil’s impurity in the process of separating Ni-Co-Mn precipitate Al and I foil.

Global recovery rates

99.96% were the Mn, Co, and Ni’s global recovery rates in this process. In the complete recovery process, Al’s product form is in its form of fool with 4.54 wt percent dissolved in the leaching process only. One can also identify Mn, Co, and Ni hydroxide precipitate’s XRD result in the precipitate. There is no identification of the Al(OH)3 phase. Also, according to findings, LiNi1/3Co1/3Mn1/3O2 cycle stability and rate performance can be increased with an enhanced lamellar structure with the help of even some AI quantity left in the precipitates, which may be present in the cathode materials.

Conclusion

With the incorporation of lithium carbonate in lithium-ion batteries, these batteries have massively increased in terms of production and applications due to the excellent features and characteristics that it brings along. However, ongoing and further research is needed to proclaim all the advantages that are provided by lithium carbonate to lithium-ion batteries in terms of enhancing their applications and products.

How ​can Graphene be used in polymeric applications

Graphene is known to be an allotrope of carbon and is always arranged and put together in the form of a lattice. These are the most used and most stable form of carbon and that is why are known throughout the world. The work mechanics that they perform are known throughout the world and make it more usable. The properties and characteristics that are exhibited by graphene polymers are highly remarkable which increases their production demand and as a result, more and more applications are applicable for this product.

Most of these applications can be seen in the field of medicine, engineering, and chemicals. A wide range of such applications is explained in this article and enlist all the ways in which graphene polymers are being used and promoted.

Introduction

Carbon has many allotropes, for instance, carbon nanotubes, fullerene, graphite, and diamond. They are all a part of the carbon family. One of the carbon family’s allotropes is known as graphene, which is a planar monolayer of sp2 hybridized carbon atoms organized in a 2-D (two-dimensional) lattice. Graphene has been observed to be the building block for all other dimensional graphic materials. For instance, just by wrapping a graphene sheet’s section, fullerenes (0-dimensional carbon allotrope, buckyballs) can be made.

Graphene nanoribbon should be rolled in order to make the carbon nanotubes (1-dimensional carbon allotropes, CNTs). Stack the graphene sheets on top of one another to make the graphite (3-dimensional carbon allotrope) and each of the sheets is separated by 3.37 A ̊.

 

Academic material

Despite being called a 3-dimensional material’s integral part, strictly 2-dimensional graphene crystals are an academic material. In 2004, Novoselov used micromechanical cleavage to isolate the free-standing single-layer graphene when graphene was separated from graphite; and then in 2005, Novoselov and Zhang used ermions for the same purpose. In 2010, graphene’s revolutionary discovery has awarded Andre Geim and Konstantin Novoselov the Nobel Prize in Physics for groundbreaking experiments.

Graphene sheet and derivatives

Graphene sheet and their derivatives have attracted a huge amount of interest during the past decade in most of the engineering and scientific areas because of their remarkable structure and extraordinary chemical and physical characteristics. In graphene, there are many qualities like high specific surface area (2600 m2g-1), good optical transparency (97.7%), remarkable thermal conductivity (3000-3000 W m-1K-1), high carrier mobility under optimum condition (2,50,000 cm2V-1s-1), and quantum hall effect.

Graphene possesses superlative electronic, thermal, and mechanical characteristics and a combination of them. Numerous synthetic routes are made for making graphene and its derivatives for exploiting these remarkable characteristics in practical applications, varying from the bottom-up epitaxial growth to graphite’s top-down exfoliation through liquid exfoliation, intercalation, and/or oxidation.

 

Use of organic and inorganic materials

Numerous inorganic and organic materials have been used to make graphene-based composites successfully, and they, therefore, are extensively utilized in applications like batteries because usually, the polymer materials possess remarkable strength, specific modulus, and broad applications in defense, automobile, and aerospace industries, etc.

Silicate fillers

In 1950, Carter developed polymer nanocomposites with exfoliated layered silicate fillers, and a report came after approximately forty years displaying major mechanical characteristic improvement utilizing clay in nylon-6 matric as a filler, therefore attracting significant industrial and academic interest in the nanocomposites. As there have been developments in nanotechnology and nano-science, many nanofillers like carbon nanotubes, nano-silica, and carbon black have been broadly utilized and studied for enhancing polymer’s electrical, thermal, mechanical, and gas barrier characteristics.

Surface to volume ratio

Due to the inner nanotube surface’s inaccessibility to the polymer molecules, graphene has a higher surface-to-volume ratio as compared to carbon nanotubes. Graphene is more favorable in enhancing the characteristics of the polymer matrices. Over some last years, there has been the incorporation of graphene and graphene’s derivatives into a broad variety of polymers, including polymethylmethacrylate (PMMA), nylon, polyaniline (PANI), polyethylene terephthalate, polypropylene (PP), polystyrene (PS), and epoxy for numerous functional applications.

Although there are some challenges and major issues in the fabrication of the advanced graphene/polymer nanocomposites. There are many factors that can affect the applications, functions, and characteristics of graphene/polymer composites. Those factors include graphene’s network structures in the matrix, interfacial interaction between the matrix and the graphene, graphene’s exfoliation and dispersion in the polymer, intrinsic characteristics of graphene and its derivatives, graphene’s type, and its derivatives type.

Properties

130 GPa and 1.0 TPa is defect-free graphene’s fracture strength and in-plane elastic modulus. RGO sheers’ measure elastic modulus is still more than or equal to 0.25 TPa despite some structural distortion through tip-induced deformation experiments. Young modulus’s chart is shown as density’s function to compare the characteristics of graphene with other traditional materials, demonstrating that the strongest and stiffest material to be ever known in nature is the defect-free graphene.

Graphene is the primary load-bearing component of polymer composites because of graphene’s remarkable intrinsic characteristics or RGO sheets (in comparison with most of the polymeric materials), coupled with their large surface areas. Thus, a huge amount of interest has been gained by graphene-filled-polymer composites, making it an extremely researched direction in composite materials now. Graphene will be incorporated into the polymers to considerably improving the mechanical characteristics. There are many benefits of graphene’s presence in the mechanical reinforcement as compared to the presence of the existing carbon fillers like SWNT (single-walled carbon nanotubes), expanded graphite (EG), and carbon black (CB).

Aqueous solution mixing method

The aqueous solution mixing method was used by Zhao et al. for developing a completely exfoliated RGO/PVA composite. The Young’s modulus is increased by almost 10 times at RGO’s 1.8 vol% and there is an increase of 150% in the tensile strength as compared to the pure PVA polymer.

The mechanical and thermal characteristics of PMMA-based composite containing EG fillers, single-walled nanotubes, and functionalized graphene sheets (FGS) were investigated and compared by Ramanathan et al. According to the results provided by Ramanathan et al., wrinkles being present can result in the roughness of the surface of nanoscale which likely forms an improved mechanical interlocking and adhesion with the polymer chains. There were investigations on the PS composite’s creep and recovery with carbon nano additives various geometrical morphologies for instance CRGO sheets, MWCNT (multi-wall carbon nanotubes), and CB.

The CRGO sheets displayed better efficiencies at a fixed loading of fillers in lessening the creep and unrecovered response as compared to the multi-walled carbon nanotube and CB fillers.

Electrical conductivity

There have been general employments of the conductive fillers for insulating polymer matrices for realizing the electrical conductivity. Percolation theory can explain this, for instance, conductive pathways are formed by conductive fillers, i.e. percolation thresholds. This simple power-law expression σc=σf[(Ф-Фc)/(1-Фc))]t, can model the increase in conductivity as a filler loading function once you have achieved the electrical percolation. In this equation, the universal critical exponent is denoted by t, the percolation threshold (onset of the transition) is denoted by Фc, the filler volume fraction is denoted by Ф, and the filler’s conductivity is presented by σf.

Conductive fillers

Graphene is a promising conductive filler for enhancing the electrical characteristics of numerous polymers because of graphene’s high electrical conductivity and large aspect ratio. RGP/PS composites’ electrical conductivity was investigated by Stankovich et al. as a function of filler volume fraction. According to the attained results, a typical percolation behavior was displayed by the RGO/PS composites, and introducing RGO to PS can enhance the conductivity to the magnitude of more than 10 orders. Folding, wrinkling, and crumpling morphologies were shown by the composites having only 1.0 vol% RGO loading and they have 0.1 S/m electrical conductivity value, which refers to the fact that one can use low-loading of graphene to construct highly conductive graphene/polymer composites.

Thermal conductivity

Graphene is not famous for its exceptional electrical and mechanical characteristics only. Its thermal conductivity makes it famous too. High intrinsic thermal conductivity of more than 3000 W/mK was exhibited by graphene and its derivatives when suspended. In 2-dimensional crystals like graphene, phonons’ physics is significantly different from 3-dimensional graphite. Lower interfacial thermal resistance is provided by the 2-dimensional geometry of graphene sheets, therefore forming highly-enhanced conductivity for the polymer composites, and imparting considerable anisotropy to polymer composite’s thermal conductivity because of the measured in-plane thermal conductivity which is 10 times more from the cross-plane conductivity.

Increase in electrical conductivity

There is nothing dramatic about the improvements in the thermal conductivity that are made by the graphene fillers unlike the exponential increase in the electrical conductivity, however, in comparison with 1-dimensional carbon nanotube, thermal conductivity can be more effectively improved by 2-dimensional graphene. The extremely small contrast in the polymer and graphene’s thermal conductivities as compared to not such a small contrast in the polymer and graphene’s electrical conductivities can explain this.

 

Applications

Graphene is a promising filler for enhancing the thermal, electrical, mechanical, and other significant characteristics of polymers according to the properties and features of graphene/polymer composites that are shared above. Despite many challenges in the development of graphene and its derivative’s fundamental understanding, there have already been much researches on their potential of having broad applications in various fields including functional materials and structural reinforcement. There have been so many studies on the usage of electronic memory devices, reinforcement, energy storage, photoelectric conversion, biomedicine, and photoelectric applications.

Structural reinforcement materials

At low graphene loading, one can obtain a considerable enhancement on polymer matrices’ mechanical performance, suggesting usage of such materials in the applications of transport that demands the combination of lightweight and high strength. Particularly, the utilization of graphene and graphene’s derivatives gave the possibility of improving the mechanical characteristics of the traditional fiber-reinforced polymer composite systems further. Only 0.2% RGO additives were seen to improve the glass fiber/epoxy composite’s fatigue life in flexural bending according to Yavari et al. The fatigue life improves, and spray-coating the RGO directly at the fiber-matrix interface produced considerable benefit over RGO’s uniform dispersion in the bulk epoxy resin.

Situ ultrasound analysis

During the cycling fatigue test, composite’s in situ ultrasound analysis suggested that the fiberglass/epoxy-matrix interface is toughened by the RGO network, preventing glass microfibers from buckling/delamination under compressive stress. Moreover, carbon fibers surface were modified by using graphene oxide and that provided enhanced interfacial characteristics in the carbon fiber/polymer composites.

When GO in low loading is introduced on the surface of the fiber, then there comes a considerate improvement in the tensile characteristics, interlaminar shear strength (ILSS), and interfacial shear strength (IFSS) of the composites. Also, combined usage of graphene nanoplatelet and carbon fiber formed dramatic thermal and mechanical increments of thermoplastic composites. There is a potential seen from these high-performance hierarchical materials in enhancing the cost-effectiveness, reliability, and safety of the fiber-reinforced polymer composites that are turning out to be the material of choice in wind energy, biomedicine, sports, marine, automotive, and aerospace industries.

Sensors

Damage and strain sensing are two main facets of the sensing responses of graphene/polymer composite materials. Graphene/polymer composites’ overall conductivity is strongly determined by the tunneling between the local conductive networks, therefore a major change will be formed in the conductivity by a change in the local tunneling distance. Thus, a major change in the conductivity can be a result of the outer-stimuli-induced changes in the tunneling distance, and that can be then monitored and further utilized for the purposes of sensing. Strain sensors can be fabricated by incorporating graphene and graphene’s derivatives including RGO, GO, and GNP sheets into an insulating polymer matrix.

Resistance variation

Electrically conductive composite’s conducting network changes when there is an application of external pressure, leading to resistance variation. This effect is known as the piezoresistive effect. Applications have been proposed in a broad range for piezoresistive materials, including movement sensors, wearable electronics, health monitoring, and smart textiles. Composites with 0.0136 vol% GNP loading and piezoresistive GNP/silicone rubber composites were made by Chen and co-workers, which is near the percolation threshold and under extremely low pressure, displays a sharp positive-pressure coefficient effect of the resistivity in the finger-pressure range.

Flexible conductor

When highly bent or stretched, high electrical conductivity can be maintained by the flexible conductor, therefore creating huge opportunities and has been interacting huge amount of interest recently. Just like the name, flexible conductors need a combination of high electrical conductivity and good mechanical flexibility which is a potential for having applications in field emission devices, Li-ion batteries, supercapacitors, stretchable solar cells, dielectric elastomer actuators, flexible electronics, wearable displays, and robot arm joints. They are being utilized for the preparation of flexible conductors because of their remarkable electrical and mechanical characteristics. Two major strategies are used generally; (i) usage of the novel formation methods. (ii) Conductive graphene filler’s compounding into a polymer matrix.

 

Rubbery polymer matrix

Compounding conducting graphene into a rubbery polymer matrix is the first method to attain a flexible conductor (PDMS) for producing elastic composites. Highly elastic conductors with 100% higher strain can be produced by the graphene/polymer composites with a low filler loading, still, its conductivity is very little to be utilized as a flexible electronic device. Devices of a high level of conductivity can be produced by the composites with a high filler loading but those devices will have poor flexibility because of the agglomeration or segregation of the fillers. One can backfill a preformed graphene/MWCNT aerogel with PDMS to obtain an effective method to produce a stretchable and highly conductive composite. With the loading of only 1.3 wt% graphene/MWCNT, the electrical conductivity reached 2.8 S/cm, and the electrical conductivity stayed constant after repeatedly stretching 100 times by 20 % and bending 5000 times.

In the 2nd strategy, conductive graphene-based fillers are integrated onto a flexible substrate utilizing numerous technologies like room temperature rubbing, etching, and transfer processes, and rod coating to develop a flexible conductor.

Graphene films

For example, a simple way was developed by Kim et al. in 2009 for the growth and transportation of stretchable graphene films of high quality on a large scale on nickel scales through the usage of CVD which can then be easily moved by simple contact methods to stretchable substrates (PDMS). Flexible RGO-based film was successfully fabricated by the usage of the rod-coating technique but they were fabricated with good transparency and low resistance made directly on the PET substrates.

RGO/PET film is used to produce a fully functional 4.5-inch four-wire resistance touch screen and it displayed linearity which can be compared with that of the ITO-based touch screens but it also displayed high mechanical flexibility which is more than the mechanical flexibility of the ITO-based touch screens, which refers to an approach that is potentially appropriate for usable RGO film’s roll-to-roll production for numerous flexible electronic devices.

Flexible lithium-ion batteries

Since flexible electronics have been invented, a huge amount of attention is gained by the flexible lithium-ion batteries as a power source as right now is the time of emergence for many wearables and flexible electronic devices like implantable medical devices, wearable sensors, conformable active radio-frequency identification tags, touch screens, and roll-up displays. There have been investigations on the graphene/polymer composite materials for Li-ion batteries for the improvement of cyclic stability and discharge/charge rate capability because of graphene’s porous networks, high electrical conductivities, and electroactive characteristics of both conductive polymers and graphene.

Electronic conductivity is significantly enhanced by the highly-dispersed graphene in the polymer composite and it also enables the efficient utilization of polymer cathode’s electrochemical activity, allowing the delivery of ultrafast discharging and charging (in few seconds, 100 mAh/g delivered). Electromagnetic interference shielding materials and electrostatic discharge shielding materials are the other applications of conductive graphene/polymer composites, and they provide potential usages from frequency shielding coatings for electronics and aircraft, telecommunication antenna, electronics packaging to the parts of mobile phone, and carpeting floor mats.

Biomedical applications

Biomedical applications have a focus on another application for graphene-based composites recently because of their biocompatibility, their remarkable characteristics, and their easy functioning. Functionalized graphene sheet’s range of potential applications starts from delivering the drug and multimodal imaging for exploiting graphene’s electrical characteristics towards the production of biosensing devices.

For example, RGO-filled glucose oxidase (GOx) biocomposite film was made by Chen and co-workers and they showed extremely high selectivity, reproducibility, and extremely good stability. Remarkable catalytic activity was especially displayed by the developed biosensor towards glucose, therefore opening up new options in the formation of biofuel cells and cheap (cost-effective) biosensors. There also have been investigations on other biodegradable and biocompatible polymer composites and RGO sheets and graphene oxide’s incorporation into polylactide, polyethylene glycol, and chitosan.

Composite chitosan films

Solution mixing is used to prepare graphene and chitosan’s composite films. According to the results of cell adhesion, L929 cells adhered to the composite films and developed on the pure chitosan films, demonstrating that good biocompatibility is possessed by the graphene/chitosan composites. The facile solution casting method was used to make RGO/PVA composite films with a nacre-like bricks-and-mortar microstructure and prepare a hybrid building block of PVA-coated graphene oxide sheets and post-reduction treatment followed it. HUVECs (human umbilical vein endothelial cells) were used to study composite film’s biocompatibility.

Cell growth

The growth of the cell can be supported by the PVA/RGO films as they are appropriate for it. On RGO/PVA films, the number of HUVECs’ cells was nearly similar to the number of cells on the TCPS (tissue culture polystyrene) plates when this attempt was made. There was no cytotoxicity and as compared to the HUVECs seeding efficiency on common TCPS plates, it was higher on the PVA/RGO films. When the excellent electrical conductivity combines with the excellent mechanical characteristics, their biocompatible characteristic turns these films into candidates for applications in biotechnology, for instance, electroactive substrates/scaffolds for biosensors, cell culture, drug delivery, and tissue engineering.

Conclusion

Graphene being the allotrope of carbon is used in various forms and one of those is in the form of polymer. The properties that graphene polymers exhibit are highly authentic and make them reliable for the applications that they then perform. All the researches that have been carried out in this regard prove the authenticity of these polymers which moves them a step ahead towards better working outcomes and benefits.

Characteristics and Applications of Dry Film Lubricants

Dry film lubricants are also known as solid film lubricants, which are responsible for minimizing the friction present in between those surfaces which are thriving in extreme environments like temperature alterations, pressure alterations, and limitations of using liquid and oil. These lubricants are prepared through a series of steps that need constant attention as these delicate steps cannot go unnoticed. After the preparation phase, when dry film lubricants are formed, they possess excellent properties and characteristics, which are the key motive of their great performance in the industries.

Depending upon these properties, the applications that are performed by dry film lubricants are considered outstanding in their nature as they are providing the industries with outclass results.

Introduction

In many extreme environments like environments with low and high pressure, low and high temperature, and where one can’t use the oils and the liquids, solid film lubricants and dry film lubricants reduces friction between the surfaces. Another interesting alternative to fluid lubricants is this coating, as it can lessen friction and prevent galling and seizing, particularly in environments of low or high temperatures where the fluids may vaporize or freeze.

A broad range of options of lubricant coatings is provided by Metal Coatings Corp. that protects the items like the smallest fasteners and huge industrial components that need a coating for the reduction in friction.

 

What are the names of the most usually utilized dry film lubricants?

Even though they can be dipped, anoplate sprays them on like paint. Perhaps, Polytetrafluoroethylene (polymer material PTFE), MoS2 (molybdenum disulfide), and inorganic compounds graphite are the most usually utilized dry film lubricants. High lubricant characteristics are possessed by them, which allows them to have applications in which friction needs to be reduced, and oils or greases need to be removed. Dry lubricants are utilized as a replacement for oils and greases. Sometimes, the dry lubricants are utilized as the “back-up” lubricant under the grease. It is done so that less addition of grease won’t be able to lead to failure.

What is grease and oil’s function?

Grease and oil perform best when shaft speeds and surface areas allow an oil film for efficient formation. However, this can be the result as long as the functioning temperatures are within a specific range of between 212 F and -4 F typically). If the machines are functioning in extreme conditions, then the lubricant’s state can change, and it can stop the formation of the fluid film. When talking about extreme conditions, we are talking extreme from the perspective of a lubricant.

Your gears would be grinding if a protective film won’t be able to be formed. However, if you don’t get a protective film, then there will be no need for a protective lubricant as it is rendered useless.

Reasons

This is the reason that why once the fluid film goes away, the particular materials are utilized for aiding in the protection of the surfaces. Those particular materials are known as dry film or solid film lubricants. These particular materials can be utilized as an additive in greases and oils and can be utilized in pure form, too (free-flowing powder). During manufacturing, they can be alloyed or added to the surface of the component, too (for instance, a non-stick cooking pan).

Protective conditions

As compared to most of the oil-based lubricating fluids, the protection that is offered by them is far superior. Upper-temperature ranges are possessed by them, and they are way more than the surface-protecting ability of most synthetic and mineral base stocks. These agents are generally utilized in conditions like extreme environmental and chemical contamination and extreme pressure and temperature.

They are utilized as an additive or in their pure form that is a free-flowing powder. Solid lubricants form boundary films that are capable of working under extreme speed, temperatures, or loads and maintain steady viscosity (thickness). However, grease and oil fluid’s viscosity that is utilized for hydrodynamic lubrication can be affected by these functioning conditions.

What are the uses of these agents?

These agents are generally utilized in conditions like extreme environmental and chemical contamination and extreme pressures and temperatures. They can be used generally as an additive or in their pure form. When solid lubricants make the boundary films, they are capable of maintaining steady viscosity (thickness) even under heavy speed, temperatures, or loads. The viscosity of grease and oil fluid films that are utilized for hydrodynamic lubrication can be affected by these conditions of operation.

What is hydrodynamic lubrication?

When the lubricant is not enough for reaching hydrodynamic lubrication, then you use these, and they are as the micro ball bearings that can aid in the separation of the two mating surfaces. This is a common occurrence with sliding, slow-moving, and heavily loaded surfaces. Molybdenum disulfide (as an additive) stays in one place till the time of the next lubrication interval. The most typical dry lubricant is molybdenum disulfide, which is usually added to the heavy-duty greases that are utilized in the equipment of construction, they are also called moly-fortified greases, but they are not the only ones.

Diverse characteristics are possessed by each material. Following are the most usual materials

  • Tungsten disulfide
  • Cerium Fluoride
  • Calcium Fluoride
  • Talc
  • Boron Nitride
  • Graphite
  • Teflon (Polytetrafluoroethylene) PTFE
  • Molybdenum disulfide (MoS2), also known as moly

Other than graphene, Teflon and graphite are the most recognized and usually utilized dry lubricants in the industry.

What are the general characteristics of Dry Film Lubricants?

Different characteristics are possessed by each solid film coating substance.

  • WS2 and MoS2 function well in a vacuum and can bear high loads.
  • High oxidation and environmental temperatures are possessed by graphite.
  • WS2 and MoS2 can’t bear detergents, and they are oilioscopic.

What are the conditions for the application of dry film coatings?

As compared to other conventional lubricants, solid-film lubricants are the perfect additives or alternatives. Following conditions are usually needed for the application of the dry film coatings:

Typical Surfaces

One can utilize solid film lubricants on all kinds of surfaces. If one wants extended service life and long-term lubrication, the perfect choice will be the dry film lubricants as they have long-term lubrication and extended service life.

Extreme Environments

Most dry coatings can function in extreme environments and high speeds, pressures, and temperatures. Liquid lubricants can also fail in some cases when the conditions are these. For instance, typical organic greases and oils can be evaporated because of the high altitude/space applications or manufacturing of the semiconductor. Dust and dirt won’t be attracted by the dry film lubricants even in the dirty and dry applications, and that characteristic will form an abrasive and gummy mixture with grease and oil.

Reciprocating Motion

A reliable lubricant determines a typical application with the reciprocating motion for minimizing wear and tear. The capability of maintaining a proper lubricating film can be lost by the liquid lubricants in extreme conditions like high temperature or pressure. Although solid or dry lubricants aid in avoiding corrosion, fretting, seizing, and galling and they do not migrate too.

What is Polytetrafluoroethylene?

If one needs the sliding action of parts, then PTFE can be utilized; for instance, it is already utilized in slide plates, gears, and plain bearings. Colorless film capacity is offered by PTFE. It has good sliding friction reduction. It also possesses good chemical resistance, and at low loads, it provides a low coefficient of friction. PTFE possesses a low load-carrying capacity.

Dry film and solid lubricants can perform a significant role in the smooth running of the world, particularly in extreme conditions. One can find solid lubricant additives in high-performance greases.

What is molybdenum disulfide?

MoS2 can lubricate even in a vacuum, and it is also utilized in space vehicles and CV joints. Molybdenum disulfide prevents stick-slip, and with increasing loads, it provides decreased friction. MoS2 protects against fretting corrosion. Molybdenum disulfide also provides remarkable adhesion, a broad service range of temperature, and a high load carrying capacity.

 

What is graphite?

Various applications use graphene, for instance, applications like ball bearings, brass instrument valves, railway track joints, and air compressors, among various others. Particles can be stuck by the liquid lubricants, and graphite is used frequently in the lubrication of the locks. Sticking particles can worsen the problem. Under high loads, graphite offers a low coefficient of friction. Even in high humidity, graphite provides good lubrication. Graphite protects against fretting corrosion and also benefits from high-temperature stability.

What is proper lubrication’s role?

If you want to maintain equipment or machinery, one of the most significant aspects isproper lubrication. Always make sure to get a lubricant (either a solid or fluid) that your original equipment manufacturer specifies when you have to choose a lubricant.

Why and How to select a dry film lubricant with a pigment?

Forming dry film lubricants with the resin binders is the same as forming corrosion prevention coatings and paints. When needed, lubricant functions as a pigment and determines the color aesthetics in this case. Formation of the film is helped by the lubricant pigments as the lubricant pigments separate the mating surfaces that are in relative motion, therefore guaranteeing corrosion and wear resistance, a lower coefficient of friction, and wear and corrosion resistance.

Basis of selection

The basis of selection for the dry film (solid) lubricants is the required performance and the environment that is needed to be endured by them. Some of the typical dry film lubricants include boron nitride (BN), indium (In), antimony oxide (Sb2O3), tungsten disulfide (WS2), fluorinated ethylene propylene (FEP), graphite, MoS2, and PTFE.

Atmospheric moisture

Graphite doesn’t need atmospheric moisture for performing as a lubricant. However, MoS2’s desirable characteristics are significantly affected by the moisture’s presence. PTFE’s wear or corrosion resistance is not impacted at all by the moisture.

MoS2

If one needs material with the capability of carrying a load as high as up to 250,000 pounds per square inch, then the perfect material for the job is MoS2. Fifty thousand pounds per square inch of load-carrying capability is possessed by graphite, and 6,000 pounds per square inch of load-carrying capability is possessed by the PTFE.

Graphite

MoS2 and PTFE can function even in temperatures of 750 F and 500 F, respectively, whereas graphite excels in thermal capacity. Solid lubricants decompose and oxidize at higher temperatures. Graphite is currently being utilized in the firearms, railway track joints, bearings, and open-gear fasteners functioning at extremely high temperatures. But, graphite is electrically conductive, which is a disadvantage as it can be the reason for corrosion too.

Fluoropolymers, for instance, PTFE, has limited thermal capacity and load-carrying capability along with a low coefficient of friction.

Boron nitride (hexagonal) is used in space vehicles’ internal parts.

Tungsten disulfide is usually utilized in space vehicles for ball bearings, but it is costly. In comparison with MoS2, tungsten disulfide possesses better frictional characteristics at higher loads and higher temperatures.

What are the resin binders?

A bond is created between the dry film lubricant and the surface that needs protection by using various types of resins as bonding agents. Corrosion resistance isn’t provided by inorganic binders like silicates, and they are not much resistant against moisture too. Although, in 538°C (1000°F ), corrosion and wear protection is ensured by a Boric Oxide (B2O3) binder along with lead sulfide (PbS) as a lubricating pigment. Although at less than 1000 F (538 C) temperatures, it does not perform as a lubricant.

What are the common types of resin binders?

Generally, the classification of the common types of resin binders that are used with solid film lubricants is as either:

 

  • Thermoplastic binders, or
  • Thermosetting binders

A solvent evaporation process, for instance, ambient air curing, is used to cure the thermoplastic binders, whereas heat energy is needed by thermosetting binders for curing. Sometimes, the thermosetting resins are not suitable for military applications because of their demands of curing temperature.

 

What are thermosetting resin binders?

Silicone resins, epoxy resins, urethanes, and phenolic resins are the famous thermosetting resin binders that are usually considered for solid film lubricants. We can also consider a mixture of resins. Although, each of the resins has its particular advantages and drawbacks. One should keep the particular end-use in mind if choosing a mixture of resins. Epoxies generate wear debris that lessens the performance of the lubrication over the long term, making the service life short. Although, good adhesion to the metallic substrates is formed by epoxies. There should not be any kind of utilization of phenolic resins in alkaline environments.

What are phenolic resins?

Phenolic resins are appropriate for high vacuum applications, and they don’t produce dangerous wear debris. Although as compared to epoxy resins, the adhesion of phenolic resins to the metals is not as good. Even though the bonding strength of silicones with metals is good, it still produces harmful debris. The reasonable bonding strength is produced by a combination of phenolics with epoxy resins with metals for general applications. High-temperature curing is needed by the ceramic resins, and that can interfere with the substrate’s metallurgical characteristics. When a resin is being selected, the main things to consider are the baking duration and the curing temperature.

What are thermoplastic resin binders with solvents?

A solvent component will be needed by the air-drying type of thermoplastic resin binders, like acrylic resins. One can achieve curing by allowing the evaporation of the solvent so that a hard coating will be formed on the intended surface by the dry film lubricant that is dispersed in the resin.

How to Apply a Formulated Resin-based Product?

What is surface pretreatment?

If there is no systematic conduction of the application process and surface preparation, then even the best formulations can fail in service. If the pretreatment includes a phosphate treatment, grit blasting with aluminum oxide (Al2O3) of 220 mesh, and vapor degreasing, then the best results are obtained for the steel surfaces.

What is the application of a Formulated Resin-based Product?

Corrosion-resistant coating application methods are the same as resin-bonded dry film lubricant application methods. In many cases, the thickness of the film should be specifically controlled for good corrosion prevention as it should be in the range of .0002 to .0005 inches. Coating application methods like brush and roll coating, electrostatic spray, dipping, and conventional spray are all applicable for resin-bonded solid lubricants too. Dimension and complexity of the parts, number of parts to be coated, and total surface area determine the final selection of the method.

Graphite/Molybdenum disulfide (MoS2) in Silicone Resin, Polytetrafluoroethylene in Phenolic Resin, and Molybdenum disulfide (MoS2) dispersed in Phenolic Resin are the typical Final Products Results. Lubricating materials of three types are the main focus of our solid dry film lubricant coating operation:

What is molybdenum disulfide?

In high load-bearing applications, protection against friction is provided by moly dry film lubricant, which is commonly known as Molybdenum Disulfide. 250,000 psi or more of Lubricant quality can be maintained by the moly coated item’s surface. Additional high-performance resins are included in most of the MoS2 coatings for enhancing their bonding with the coated part’s base metal.

What is xylan?

In a matrix of stable and strong organic polymers, the mixture of the fluoropolymer compounds with low-friction is known as Xylan®. Resistance to chemicals, corrosion, cold, heat, and friction is provided by this fluoropolymer coating along with remarkable surface wear characteristics.

What are fluoropolymer coatings?

They form a slick, hard, and smooth finish and are the best solid/dry film lubricants. One coat system is used to apply these coatings as it can cause these coatings to fuse to the substrate for excellent adhesion.

What is air-assisted spray application and preparation of aqueous-based dry film lubricant formulations containing sucrose?

Sucrose was included in starch-oil composites aqueous dispersions for determining if the starch–oil composite dry film lubricant’s thin films lessened COF as efficiently as the previous coatings did that were previously applied with doctor blades. The starch–oil composite dry film lubricants thin films were air-sprayed onto the metal surfaces. In the earlier formulations, sucrose was needed for promoting flexibility and adhesion to the thicker composite coatings as these coatings peeled off and cracked the metal surfaces and were made without sucrose. The current study shows that in the formulation of aqueous dry film lubricant, the concentration of sucrose was within the ranges and maintained between 8.4 and 5.7 wt%.

Siphon feed spray gun

Starch-oil composite’s aqueous dispersions were applied by using a siphon feed spray gun. It was a high-pressure area’s low volume flow that applied the aqueous dispersion and shaped its pattern after it was discharged from the nozzle assembly.

What are the methods of application of the dry film coatings?

Following are the ways to apply dry film coatings.

  • Composites: Solid film lubricants can be generally alloyed into sintered materials and polymers to enhance particular characteristics.
  • Impingement Coatings: Impingement coatings are anti-friction coatings. They are tungsten disulfide (WS2) and molybdenum disulfide (MoS2) that don’t need a curing process and are capable of being applied at room temperature. These coatings are of less than 0.0001″, making them extremely thin, and they do not affect the tolerances of normal machinery. They are capable of functioning as the sole lubricant. They also perform well with hydrocarbon-based greases and oils.
  • Dipping/Spraying/ and Brushing: One can add solid film lubricants to specified binders and resins. The application of lubricants is made on the specified components that, after the assembly, are usually not accessible for lubrication. The component’s base material determines the availability of numerous thermal cure and air cure products.

Conclusion

Dry film lubricants have three main types in which they perform and excel marvelously. This is due to the excellent properties that these lubricants possess and ultimately are the cause of enhancing their productivity. However, the applications of dry film lubricants are quite interesting and effective for the massive growth of our industries in a lot of ways because they play a pivotal role in daily lives as well.

​Solid-state Silicon batteries Properties and Applications

Solid-state silicon batteries are one of the subclasses of lithium-ion batteries which are one of the best-known batteries in the market. In these batteries, a silicon-based anode is present at one electrode which is responsible for the carrying of charge. Silicon is an excellent material and has a very high specific capacity because of which markets have started incorporating them in lithium-ion batteries.

Their characteristics and properties are highly efficient owing to the environment in which they are used. This has massively increased their applications and usage in daily life as well mainly the portable electronic devices and technology.

Introduction

Silicon batteries are a subclass of lithium-ion batteries and this happens when silicon is used as an anode and lithium ions work as the charge carriers. It is observed that the silicon materials are capable of having a much larger specific capacity which is equal to 3600 mAh/g in the case of pristine silicon whereas comparatively graphite has occupies a specific capacity range as 372 mAh/g.

Volume change

Silicon has a large volume change which is equivalent to almost 400% relying upon the crystallographic densities. This happens when lithium is used to tackle the obstacles having a highly reactive state so that the anode of a silicon battery can be commercialized.

 

Battery anodes

All the commercial battery anodes possess little range of silicon to affect their performance positively. These ranges are not known or told as they are kept secretive but it is assumed to be 10% of the entire anode. These silicon batteries contain the cell configurations in which Si is present in those compounds which have low voltage and then become capable of storing lithium via a displacement reaction which includes silicon oxycarbide, silicon monoxide, or silicon nitride.

Anode material

Silicon has been proved as an excellent material to be studied and used as an anode material for lithium-ion batteries as it has a high specific capacity which is excellent for these batteries. During this entire process, the anode materials based upon silicon suffer in terms of huge volume changes which go on in the process of charging and discharging. This leads to certain side reactions, electric contact is lost and pulverization of silicon occurs too. These changes may hinder the commercialization process of silicon as they promote poor cycle life.

Lithiation and delithiation

Lithiation and delithiation behaviors and processes are also studied in this regard as these include interphase reaction mechanisms. There are a lot of nanostructured silicon anodes which portray high specific capacity and cycle life, both in comparison to the commercially based carbon anodes. Nonetheless, a few issues do exist in this nanostructured silicon which can never be ignored and for that, a lot of researches have been carried out to come to a conclusion and eradicate all the hurdles which hinder the working processes of commercial lithium-ion batteries.

Performance of silicon anodes

It is evident from all the studies, researches, and experiments that silicon anodes work far better than all the other materials used as anodes due to the compatibility and efficacy that they bring forth and enhance the life and health of batteries. Developments have been made over the past years to maintain the credibility of silicon anodes as it is necessary to have a keen observation for their defaults and maintenance. There are some important factors for the successful commercialization of silicon anodes that need to be followed strictly including the development of silicon electrodes with high potency materials and silicon-based lithium-ion batteries.

Dependence on non-renewable energy

In recent times, it has been highly observed that mankind has become dependent on non-renewable energy which has sparked major concerns regarding the environment, human beings and their health, and the climate which surrounds them. All of this has led to highlighting the prominence of developing and emphasizing clean energy uses. The same efforts are being made in the technological world too so that a better world can be created for everyone to feel safe and healthy. Clean energy uses are being mandatory and their use is being emphasized for all the batteries that are now being worked on or are in the process of recreation. It is a very important step in building up a safe world for upcoming generations while keeping technological safety in mind too.

Energy storage technology

In the technological market, energy storage mechanisms are being adopted for the better working of portable electronic devices and bringing a change in the different technological markets which mainly includes grid-scale energy storage. Lithium-ion batteries have also been on the same ground and have adopted this energy storage technology practice. Due to this, lithium-ion batteries have made their mark in the technological market owing to the specifications that these bring forth. Solid-state silicon batteries come under the same category and are the key ones to bring a change in the market. The applications have massively increased due to the usage of silicon in forming the anodes.

Characteristics of silicon anodes

Silicon anodes are the building blocks of solid-state silicon batteries due to the characteristics that these possess. These include high specific capacity ranges, good battery sizes with efficient life and health, and less costly. All these characteristics add up to the efficient working of solid-state silicon batteries. When all these characteristics are combined for the proper functioning and processing of the battery, they initiate a series of reactions that are highly beneficial for the battery itself and the products that these become a part of, mainly the portable devices.

Energy density

There is a long-term goal set for the better functioning of silicon batteries by USABC. This states that the pack system for lithium-ion battery must have to reach 235 Wh kg-1 or 500 Wh L -1 while having a discharge rate that is equivalent to 1/3 C. This is equivalent to 1000 cycles which possess the requirement of 15 years calendar life.

The potential of silicon

Silicon when used as an anode for rechargeable li-ion batteries, works the best to enhance the energy density of Li-ion batteries as it is a material that contains high theoretical capacity and very low potential of the electrodes in the case of solid-state. However, researches and experiments are an ongoing process to add up to the quality of solid-state silicon batteries which not only enhance the working of batteries but also pave a way for the invention of various other updated things. This is not an easy-going process and requires constant hard work and keen observations, all of which are continued.

Decrepitation

In electron conductions and Li-ion pathways, breaks are made because of the decrepitation or fracture, thus causing capacity fading and increasing the electrode resistance during cycling. Relevant differential capacity curves were used to identify rapid and gradual increases during cycling in the electrode resistance for the 3- and 1- µm-thick non-porous films. The positions of the discharging and charging peaks continue towards more positive and negative potentials as the cycling continues. As the cycling continues, the peak currents correspondingly decrease. Remarkable cycling stabilities were displayed by the porous films as compared to the non-porous films. 3000 mAh g-1 of high capacities were delivered by both of the films and after 100 cycles, they exhibited more than 93 percent of their 10th cycle’s capacities and high Coulombic efficiencies going more than 99.8%.

Peaks Position

There was no virtual change in the positions of all peaks in the differential capacity plots for the porous films, which proves that during cycling there is structural stability. For the thick and non-porous film, the Increase in the electrode impedance was excellent according to the electrochemical impedance spectra that were measured after the cycling performance tests, showing the fast capacity fading. When 0.6 mAh cm-2 was the areal capacity, there were not many distinguishing differences shown by the porous and nonporous films after the cycling between their impedance spectra.

Differences in impedance spectra

There were proper differences in the impedance spectra between the porous and non-porous films with 2 mAh cm−2 of areal capacity. As compared to the porous film, they are more in the non-porous film, suggesting that both increasing the film’s interfacial charge transfer resistance and lowering the Li-ion diffusivity causes the capacity to fade in the thicker non-porous film.

Cycled films

An electron microscope was used to observe the cycled films that were taken out from the cells for identifying the morphological changes in the cycled anodes which are the reasons for the major differences in the cycling stability in between the thicker films. After 100 cycles, the pores stayed in the porous film with a little expansion in their diameters and the width and density of the cycled non-porous film’s through-thickness cracks were broader and higher as compared to that of the cycled porous film. It is suggested by the narrower cracks with lower density for the porous film that the changes in the outer shape are suppressed by the pores via accommodation of volume expansion for lessening the increase in the resistance and maintaining the contact to the solid electrolyte.

High-rate characteristics

At last, there should be a discussion on the impact of the pore on the rate capability. In porous materials, the rate capability is normally improved when mixed with the liquid electrolytes due to the pores being filled with the liquid electrolyte as it shortens the Li diffusion length and enlarges the surface of the electrode. Solid electrolytes don’t enter the pores and the solid system’s rate capability could be worsened by the porous structure as for the electrode reactions, Li diffuses through extremely thin pore walls which in the delithiated state are of 10nm in thickness.

Repetitive large volume

Upon delithiation/lithiation, repetitive large volume change acts to pulverize or decrepitate Si particles. Recently, it was revealed by an in situ TEM (transmission electron microscopy) study that the 870 nm of the diameter of amorphous Si nanospheres, which is more than 150 nm of critical diameter, do not fracture. Thus, in solid electrolytes, anode film’s remarkable cycling performance is because of its amorphous nature with submicrometre dimensions, and morphology confinement, and suppression of production of SEI via the solid electrolyte. The thickness of the films should be more than 3 micrometers for attaining 2 mAh cm-2 of practical areal capacity.

Critical fracture diameter

There has been a recent increase in the liquid electrolytes critical fracture diameter for porous Si particles to 1.5 micrometers. There have been extensive studies on the usage of porous materials in Li-ion batteries as electrodes with liquid electrolytes. The electrode surface area is increased by the pore walls in such systems by functioning as the reaction surfaces when the pores are infiltrated by the electrolyte. The length of the Li diffusion is lessened to the thickness of the pore wall. But due to the solid-electrolyte particles not being capable of entering the pores, these benefits are not present in those solid-state batteries. Also, the anode’s structural integrity is strengthened by the porous structure and it also improves Si films cycling stability in the solid electrolytes with enough thickness for practical applications.

Cycling characteristics

There are notes and observations of the capacities of porous and non-porous film anodes. Porous Si films profiles are approximately the same as the profiles of the non-porous films and it’s also the same as the profiles of the 0.3-µm-thick amorphous Si films that were reported previously in a thiophosphate-based solid electrolyte. It is indicated by these results that the amorphous Si phase, making the pore walls is the reason for the electrode reaction. There were major differences in the porous and non-porous films’ cycling performance, the performance was dramatically enhanced by the porous structure.

According to situ

The amorphous spheres of 870 nm of diameter do not fracture according to the in situ TEM observation of lithiation of amorphous Si nanospheres. The critical value of film thickness was exceeded by the films whose thickness was examined in this study (3 and 1 micrometer for non-porous films), and therefore capacity fading was shown by the non-porous films, which the increasing thickness accelerated. Only 47% of capacity was showed by the 3-µmthick film at the 10th cycle after 100 cycles, whereas for the 1-micrometer thick film, 82% was the capacity retained. According to these results, it can be seen that while the fading capacity in the thin films with thickness a little above the limit is moderate when the thickness is increased, it also increases significantly together.

Amorphous Si films

The extremely high-rate capability was displayed by the amorphous Si films, for instance, extremely small activation and diffusion overvoltages, and therefore for solid-state electrochemical cells in this study, the dominant factor that’s observed in the polarization is the resistance overvoltage in the electrolyte layer. Thus polarization arising from the electrolyte layer resistance was excluded to obtain the discharge curves for comparing the rate capabilities inherent in the films. According to the results, the non-porous and porous films have almost identical discharge curves which show that rate capability is not detrimentally affected by the introduction of the pores.

Maintenance

At 2 mA cm-2 of current density, >2 mAh cm-2 of a remarkable high areal capacity was delivered by the thicker films, and even at 10 mA cm−2 (17 C), greater than 3000 mAh g−1 of discharge capacities were maintained by the thinner films. Discharge capacities of more than 1.2 mAh cm-2 and 1700 mAh g-1 were shown by the films even at 10 mA cm-2 of higher current density (3C discharge rate). According to these results, in the porous form, the amorphous Si’s high rate capability in the solid electrolytes is retained.

Lithium-ion Battery

Characterization and Synthesis of amorphous Si films

Radio-frequency magnetron sputtering (Advanced Optics Vacuum Co., Ltd, SPAD-2240UM) was used to deposit amorphous Si films at glancing angle geometry from a 5N-pure Si target (Kojundo Chemical Laboratory Co., Ltd) with a 30° angle between the substrate normal and the target, maintaining the temperature of the substrate at 100 °C and the substrate bias at 5 V. 15 cm was the distance between the target and the substrate.

Substrates

4000-grit sandpaper was used to polish the substrates of 10-mm-diameter stainless-steel disks. Ultrasonic treatment in acetone was used to clean them (99.5% purity, Wako Pure Chemical Industries, Ltd), and they were annealed before deposition at 800 °C in a vacuum. Si films were deposited through a mask with 8.5 mm of opening diameter for eliminating the loss of the active material that’s deposited on the substrate disks’ side.

Thickness

A surface profiler was used for measuring the thickness of the attained films whereas an electric microbalance was used for measuring the weight of the films. A scanning transmission electron microscope and a field-emission scanning electron microscope were used for observing the obtained film’s cross-sectional and surface morphologies. After the deposition of a protective carbon layer, a multi-beam processing system (JIB-4501, JEOL Ltd) was used to prepare the specimens and that system incorporated a focused ion beam (FIB) milling and a thermionic scanning electron microscope.

Characterization of obtained film’s crystallinity

The GIXRD measurements were done on a diffractometer by SmartLab, Rigaku Corp. for characterizing the obtained film’s crystallinity, and in it, Cu Kα was utilized at 45 kV of operating voltage as the radiation source in parallel beam mode. The incident X-rays’ grazing angle was 0.25 as compared to the sample surface’s grazing angle, There was the collection of the diffraction data in the two thetas (2θ) range from 90° to 3°.

Laser beam

A cylindrical lens was used to shape the laser beam into a line. Then an objective lens with 0.70 of numerical aperture and 50× magnification 8: used to focus that line onto the surface of the sample. At the sample, 100 µW was the power of the laser. The same objective lens was also used to collect the backward Raman scattering signals from the illuminated line and send it through a 70-µm-wide entrance slit into a high-resolution spectrometer. With 15 seconds of integration time, all Raman scattering spectra were attained as eight spectra’s averages. There was the calibration of wave numbers by reference to Ne’s emission lines.

Electrochemical measurements and Cell fabrication

They utilized a thiophosphate-based solid electrolyte, 80Li2S20P2S5 glass for the electrochemical measurements. According to the reports in the literature, mechanical milling was done to synthesize it with some little modifications. A pestle and an agate mortar were used to manually mix the P2S5 crystalline powders (99% purity, Sigma-Aldrich Co. LLC) and Li2S crystalline powders (99% purity, Furukawa Co., Ltd) in a 4:1 molar ratio. At 1:16 of powder-to-ball ratio, they placed the mixture (2g) with 45 ml inner volume into a zirconium oxide pot along with zirconium oxide balls that are 5 mm in diameter. They sealed the pot under an Ar atmosphere and a planetary micro mill was used to perform high-energy ball-milling at 25 °C (Pulverisette 7 classic line, Fritsch GmbH).

Attachment of amorphous Si film

To make the working of solid-state silicon batteries better, the use of amorphous Si film has been introduced in the market. In this case, the amorphous Si film is attached to the electrolyte so a working electrode can come into existence. This initiates the counter electrode at the opposite side which is done by attaching a 10mm diameter disk of Li metal foil which is formed after a hole is punched through a Li metal foil. These disks are pressed together at the rate of ~120 MPa which is done through a battery cell that gets prepared in the lab as its bolts are tightened so it can act as a two-electrode cell. It is important to keep a check on the porous structures that are formed that can either tolerate the pressure which is applied while assembling the cell.

Conclusion

Solid-state silicon batteries are considered as one of the best categories of lithium-ion batteries as their working has massively impacted the technology market and still going strong. Silicon is an excellent material and therefore has made its mark in this regard owing to the excellent characteristics that these batteries possess.

​Strategies for improving rechargeable lithium-ion batteries

Lithium-ion batteries are the kind of batteries in which lithium ions are present which are responsible for the carrying of charge from the negative electrode to the positive electrode and vice versa. There are certain types and ways in which these Li-ion batteries process and one of the most worked and authenticated ways is the utilization of rechargeable lithium-ion batteries.

They are being used at a great level owing to the potential that they have and the characteristics that these bring forth. In recent times their use in the market has been accelerated and for that certain strategies have been made to improve the working of these rechargeable lithium-ion batteries. All these strategies when either used separately or together make a huge difference and add up to the credibility of these batteries.

Introduction

Typically a lithium-ion battery is also known as a Li battery which is one of the types of rechargeable batteries found in the market. In rechargeable Li batteries, the Li-ions carry the charge from the negative end towards the positive end. This process is carried out with the help of an electrolyte and is done during the discharge process. Two different materials are used at both ends of the battery. Intercalated lithium is used at the positive electrode end whereas graphite is used at the negative electrode end. These batteries are most certainly used for electric vehicles and electronics that are portable. They have a great reach in military and aerospace areas as well.

 

Characteristics of li-ion batteries

The three basic characteristics that are interpreted by the Li-ion batteries are as follows:

  • High energy density.
  • No memory effect at all except for the LFP cells.
  • Low self-discharge.

There are different purposes for the manufacture of cells which can be either done to give prioritization to energy or power up the density. Like everything comes in the market with a lot of perks, there can be a few safety hazards as well in regards to these as they consist of electrolytes which are highly flammable and once they are left untreated in terms of charging can cause serious damages and harms.

Prototype Li-ion battery

In 1985, Akira Yoshino first came up with the idea of a prototype Li-ion battery and developed it by keeping in view the research that was previously carried out by John Goodenough and his fellows in the early 1970s and 1980s. Later in 1991, another type of Li-ion battery was developed by Yoshino.

Li-ion battery

Lithium polymer batteries

Lithium polymer batteries are the ones that comprise a polymer gel as an electrolyte, a cobalt oxide comprising of lithium as a cathode material, and graphite as an anode. All of these when combined bring forth a high energy density battery. These offer longer lives and their rate capability is much better than the rest. Their use is evident in mostly medical supplies and electric tools.

Research

According to research, lithium-ion batteries have a wide range of characteristics that add up to the goodwill of these batteries which include long-lasting life, high energy density, and enhanced safety measurements, less cost, and increased charge speed. It highly supports the idea of rechargeable batteries as these are considered one of the best-known batteries for the characteristics that these bring forth.

Electrochemistry

It is known well that certain electrochemical reactions are going on in any cell. Likewise in a lithium-ion cell, the reactants which are present and responsible for carrying out the reaction are anode and cathode materials which are compounds comprising of lithium atoms.

Oxidation

In lithium-ion cells, an oxidation half-reaction is carried out at an anode which is responsible for producing lithium ions as the positive charge and electrons as the negatively charged. This reaction may as well be responsible for the production of an uncharged material that stays at the anode. The li-ions which work as the positive charge move via an electrolyte whereas the electrons which work as a negative charge move via an external circuit and eventually they combine at the cathode in addition to the cathode materials which then becomes a reduction half-reaction.

Reduction

In this reaction, the electrolyte and external circuit are responsible for providing the charge to both, lithium ions and electrons. However, these are not involved in any electrochemical reaction. In the process of discharge, the electrons present at the anode move towards the cathode via an external circuit. In the process of discharge, reactions are capable of lowering the chemical potential of the cell and the energy in return is shifted from the cell to wherever the electric current is being transferred which is mostly in the external circuit.

The direction of movement

In the case of charging reaction and transports both moves in opposite directions. Electrons travel from the positive electrode following to the negative electrode via an external circuit. This way the external circuit is also responsible for providing the electric energy to charge the cell. The energy which is produced is now stored and named as chemical energy in the cell.

Liquid electrolytes

Lithium-ion batteries also consist of liquid electrolytes which comprise lithium salts such as LiPF6, LiBF4, or LiClO4.

Liquid electrolyte serves as a pathway of conduction for the process of discharge while cations move from the negative electrodes towards the positive electrodes. There is a combination that goes around consisting of linear and cyclic carbonates. These consist of ethylene carbonate formally known as EC and dimethyl carbonate formally known as DMC. High conductivity and SEI which is known as solid electrolyte interphase, forming ability is offered via this combination.

Organic solvents

During charge, organic solvents are capable of decomposing on negative electrodes. Usage of appropriate organic solvents is very important and when it is carried out then the solvent becomes capable of decomposing on initial charge as a result of which a solid layer is formed known as the solid electrolyte interphase. Solid electrolyte interphase is usually electrically insulating yet is capable of providing iconic conductivity. However, the best thing about interphase is that it stops any additional decomposition of the electrolyte after the second charge.

Composite electrolytes

Composite electrolytes are usually based on polyoxyethylene also known as POE and are responsible for providing a stable interface. It is present in two forms, liquid and solid. When present in solid form it comprises of higher molecular weight and is suitable for use in dry Li-polymer cells. While when present in liquid form it comprises of lower molecular weight and is suitable for use in regular lithium-ion cells. One of the approaches to decreasing the flammability and volatility of organic solvents is the RTIL approach known as room temperature ionic liquids.

Charging and discharging

There are two types of processes which are carried out, one is charging and the other one is discharging.

Discharge

In the process of discharge, lithium ions are responsible for carrying out the current within the battery from negative towards positive and no external force or circuit is used. However, it is done via a non-aqueous electrolyte and a separate diaphragm.

Charging

In the process of charging, the opposite of discharging is done for which an external power source is required for the application of overvoltage to make it possible for the current to follow within the battery from positive towards the negative electrode. In this way, the lithium ions become capable of moving from the positive to the negative electrode, and this process is then known as intercalation as the ions embedded in the electrode material in this process.

Energy loss

A certain amount of energy loss arises due to the electrical contact resistance at the interfaces which is calculated to be about 20 percent of the entire energy present in the batteries.

Charging procedures

There is a complete set of charging procedures for a li-ion cell and a complete li-ion battery separately and both of these slightly vary from each other.

A single Li-ion cell is categorized in two stages following which it can charge:

  • Constant current (CC).
  • Constant voltage (CV).

A Li-ion battery (the one which comprises a series of Li-ion cells) is categorized in three stages following which it can be charged:

  • Constant current.
  • Balance (not required once a battery is balanced).
  • Constant voltage.

There is a phase known as the constant current phase in which constant current to the battery is applied by the charger while increasing the voltage gradually till the time when the voltage reaches the limit of the cell.

Charging temperature limits

There are certain charging temperature limits for lithium-ion batteries but because these batteries are rechargeable so their charging limits are stricter as compared to the operating limits. It is observed that the chemistry of lithium ions performs better when the temperatures are increased but it is important to keep in mind that excessive exposure to heat is destructive for the battery health and life. They perform excellently when charged at lower temperatures and also activate the ‘fast charging’ system of the battery. The temperature range for this should be 5 to 45°C as it is considered the best temperature range for charging.

Low temperature

When the temperature is dropped down and is brought in the range of 0 to 5 °C then the current of charge should be massively reduced yet charging is possible. When the low-temperature charge is going on then a slight increase in temperature is proved advantageous as it happens because of the internal resistance of a cell.

However, keeping the required temperature limits is very much important for the proper charging of lithium-ion batteries because it will directly affect the working mechanics of the battery and will add up to the battery’s life and health.

Strategies for improving rechargeable lithium-ion batteries

Intercalation cathodes

The use of intercalation cathodes has been introduced as one of the greatest strategies to improve the working mechanics of rechargeable lithium-ion batteries. These intercalation cathodes have four different crystalline structures named layered, spinel, olivine, and tavorite. It has been proven that a lot of different materials can work up as intercalation cathodes but the transition materials and polyanion have been emerged as the best choice owing to their excellent operating voltages. The maximum specific capacity range for these oxide cathodes is said to be ∼150–200 mA h/g at the cathode level. However, researches are being carried out in this regard to achieve a high specific capacity range for these intercalation cathodes because it will be regarded as another strategy to improve the working of rechargeable lithium-ion batteries.

Layered intercalation cathodes

The first type of intercalation cathodes is the layered intercalation cathodes but Whittingham and Gamble were the first ones to develop these intercalation cathodes in 1975. Although, it was due to the low voltage value that the first-ever intercalation cathodes were changed with the layered ones, the formula for which is LiMO2. The reason behind shifting to these cathodes was that they possess high values of operating voltages and despite that high theoretical specific capacity as well.

LCO

Then came Goodenough who introduced LCO as a cathode that can be alternatively used which was later on commercially launched by SONY too. This material comparatively possessed more capacity but its cost was a little too high. Other than that it has some weird structural defects as well which enable it to suffer from fast capacity fade.

Other oxides

Additionally, a lot of other isostructural oxides have also been considered for use as a cathode for lithium-ion batteries keeping in mind the budget and statistics. The alternative options included LNO and LiMnO2, both of which are cheaper but thermally unstable too which excludes them from the working categories.

Spinel intercalation cathodes

It was proposed by Thackeray et al., in 1983 that the product LiMn2O4 is one of the best products to be used as an intercalating cathode as its specific capacity range is ∼150 mA h/g. This product is also known as LMO. The structure of LMO is spinel and in its structure, Li is located at the tetrahedral sites whereas Mn is located at the octahedral sites. The reason for using LMO as an intercalating cathode is that comparatively, it is cheap and environment friendly though it does have a little drawback which is the cycling stability. It is poor in the case of Mn as it has the property of dissolving in two electrolytes known to be LiPF6 and LiAsF6.

Result

As a result, it has been reported that the spinel intercalation cathodes are effective when used appropriately to serve the purpose of improving rechargeable lithium-ion batteries. It is important to know the characteristics of materials being used and then incorporate them in the industrial uses to be sure of what they can bring to the table. The researches and experiments have proved that ever since the spinel intercalation cathodes have been introduced in the market, the efficacy and working of rechargeable lithium-ion batteries has increased which makes them sustainable and an important material as they add up to the value of products that they become a part of.

Olivine intercalation cathodes

Olivine phosphates known as LiMPO4 as well as olivine silicates known as Li2MSiO4 are the materials in which M = Fe, Mn, Mg, and Co are considered as the cathode materials. There are some layered cathode categories as well which comparatively possess more stability and power capability. These are known as the LCO and LNO cathodes. LFP has been previously used as a conversion type cathode in lithium-ion batteries but it has been observed that the circuit potential and electrical conductivity are relatively less portrayed and to increase that several dopants have been brought to use too which aid in increasing the conductivity for LFP.

New approach

However, a new approach has been introduced which is extremely beneficial when it comes to incorporating the materials that can work great as conversion type cathodes in lithium-ion batteries. All of these techniques are responsible for taking care of the charging current and the rate at which it flows and for that the use of vertically aligned carbon nanotubes also known as VACNTs has been introduced in this market.

Result

As a result, the technique of using olivine intercalation cathodes for the improvement of lithium-ion batteries is considered very beneficial as they notably add up to the betterment and bring forth better opportunities for these batteries.

Conversion-type cathodes

The first commercial launch of lithium-ion batteries was conducted by SONY in 1991 and from that time, constant improvement strategies have been emerging for the better working of these batteries. In recent times the alternate materials that are used as a conversion type cathode have been the mode of attraction due to the practicality that they bring forth. There are a lot of conversion type AMs but out of all those, sulfur is considered as the best one for all the portable devices that are next generation as it possesses 1,675 mA h/g as its high theoretical gravimetric capacity and 2,500 W h/kg as its gravimetric energy density yet its best feature is the low cost.

Efficacy of sulfur

Though it does bring along certain challenges too which can be overcome through proper strategy making and following that strategic planning. This will not only increase the battery life but will also add up to the better working of the entire battery as well as the product that this battery will be a part of. Sulfur is an excellent product and when it is used as a conversion type cathode it promotes better battery health which is the factor for the proper functioning of the battery. However, it is important to stay updated with researches and continue to add and subtract from the advancements as per the researches.

Intercalating anodes

The graphite anodes are the ones that contain ∼372 mA h/g as their theoretical capacity. Their initial purpose is to allow the li-ion batteries to have a commercially viable approach maintaining their low cost yet great stability as this is the key factor due to which these batteries are widely being used. The principle on which these graphitic anodes work is that the Li-ions start intercalating in between the graphene planes as it is capable of giving out great 2D stability mechanically, excellent electric conductivity, and overall ionic transport. Carbon has various forms which can be used as anode graphite being the greatest of all and the rest include carbon fibers, rGO, CNTS, and exfoliated graphene. Recently, due to the wide use of rechargeable lithium-ion batteries, the demand for new and updated anode materials has excessively increased as to promote commercially good and stable anodes to maintain the excellent working of these batteries.

Efficacy of rechargeable lithium-ion batteries:

Rechargeable lithium-ion batteries are extremely beneficial and hold great importance in the market as these bring along a lot of ease and mastery to the products and processes that they are a part of. A lot of strategies have been mentioned in the article which can help improve the working of rechargeable lithium-ion batteries but it is important to follow them step by step and avoid all those which can drastically harm the battery or the product that they become a part of. In this way, industries can ensure that these batteries will be up to the mark because initially as well the characteristics and the properties that these batteries are built on are great and ensure the smooth running of the products.

Conclusion

A huge number of strategies are introduced now and then to improve the efficacy of ongoing materials or products. The same is the case with lithium-ion batteries. All these strategies have been formulated under strict observance and after all the experimental works, they have been chosen to put forward for the industries to start introducing these strategies. In this way, the efficacy of rechargeable lithium-ion batteries can be improved and enhanced massively. It is very important to stay updated with all the new strategies and advancements in the previous ones to incorporate those changes in the products and industries.

Effects and differences of MoS2 and PTFE coatings

Molybdenum disulfide is basically an inorganic compound that comprises sulfur and molybdenum, and it is also known as MoS2 as this is its chemical formula. Polytetrafluoroethylene is basically a fluoropolymer comprised of tetrafluoroethylene and is also commonly known as PTFE. Both MoS2 and PTFE compounds are highly authenticated as their characteristics and properties are unique and favourable to our industries. They have a lot of applications in different industries which openly present the effects of both these products.

They are extremely effective in their nature, and that is why their productivity has massively increased over the past years. However, the two products can be equally effective but being different; they do possess some differences too, and the same is the case with MoS2 and PTFE coated materials. These differences are not too huge, but they cannot be ignored as well. All the certain effects and differences are explained briefly in this article.

Introduction

An inorganic compound made up of sulfur and molybdenum is known as molybdenum disulfide (or moly). MoS2 is the chemical formula of molybdenum disulfide. Molybdenum disulfide is classified as a transition metal dichalcogenide. Molybdenum disulfide is a silvery black solid. Molybdenum’s principal ore is MoS2, and it takes place as the molybdenite mineral. In comparison, MoS2 is not reactive. Oxygen and dilute acids don’t affect it.

Molybdenum disulfide’s feel and appearance are the same as that of graphite. Due to its robustness and low friction, MoS2 is broadly utilized as a dry lubricant. Like silicon, bulk molybdenum disulfide is an indirect bandgap, diamagnetic semiconductor, and has 1.23 eV of the bandgap.

Synthesis

Naturally, MoS2 is found as either jordisite or molybdenite. Jordisite is molybdenite’s rare low-temperature form, whereas molybdenite is a crystalline mineral. Flotation processes molybdenite ore for giving comparatively pure MoS2. Carbon is the major contaminant. When molybdenum compounds are virtually going through thermal treatment with elemental sulfur or hydrogen sulfide, then MoS2 is formed, and it can also be formed by the metathesis reactions from the molybdenum pentachloride.

Mechanical properties

It is because of its low coefficient of friction and layered structure that molybdenum disulfide is an excellent lubricating material. When a material is applied with shear stress, energy is dissipated by interlayer sliding. A huge amount of researches has been done for characterizing MoS2’s shear strength and coefficient of friction in numerous atmospheres. As the coefficient of friction increases, molybdenum disulfide’s shear strength also increases, and such characteristic is known as superlubricity. 0.150 was MoS2’s coefficient of friction at ambient conditions, with 56.0 MPa of estimated shear strength. According to the direct methods of shear strength’s measurement, the value is near 25.3 MPa.

Wear resistance

Doping molybdenum disulfide with chromium can increase MoS2’s wear resistance in lubricating applications. According to the micro indentation experiments on Cr-doped molybdenum disulfide’s nanopillars, the yield strength for pure molybdenum disulfide increased by 50 at. % Cr from an average of 821 MPa (0 at. % Cr) to 1017 MPa. The change in the material’s failure mode accompanies the increase in the yield strength. As the increasing quantity of dopant loads the material, brittle fracture mode turns apparent, whereas the pure molybdenum disulfide nanopillar fails through a plastic bending mechanism.

Micromechanical exfoliation

It is a broadly utilized method, and it is studied in detail in molybdenum disulfide for understanding delamination’s mechanism in flakes of some-layers to multi-layer flakes. Cleavage’s exact mechanism was layer dependent. The flakes that are thin than 5 layers go through rippling and homogenous bending, whereas interlayer sliding is used to delaminate the flakes with a thickness of almost 10 layers. During micromechanical cleavage, a kinking mechanism is displayed by the flakes of more than 20 layers. The nature of Van der Waals bonding is the reason why the cleavage of these flakes is reversible.

Crystalline phases

A layered structure is possessed by all molybdenum disulfide’s forms, in which planes of sulfide ions sandwiches a plane of molybdenum atoms. MoS2’s monolayer is formed by these three strata. Stacked monolayers make up bulk MoS2, and weak Van der Waals interactions are used to hold those stacked monolayers closely together. Crystalline molybdenum disulfide occurs in nature in two phases that are, 3R-MoS2 and 2H-MoS2. In these phases, “R” indicates rhombohedral symmetry, whereas “H” indicates hexagonal symmetry.

Each molybdenum atom in both of these structures is covalently bonded to 6 sulfide ions and exists at the trigonal prismatic coordination sphere’s centre. Pyramidal coordination is possessed by each sulfur atom, and each sulfur atom is also bonded to three molybdenum atoms. Both 3R- and 2H- phases are semiconducting.

Metastable crystalline phase

Intercalation of 2H-MoS2 with the alkali metals discovered a third metastable crystalline phase which is also called 1T-MoS2. This phase is metallic and possesses a tetragonal symmetry. Doping with rhenium or other electron donors can stabilize the 1T-phase, or microwave radiation is done to convert it back to the 2H-phase.

 

Effect of MoS2

Electronic applications

MoS2 has many good qualities, but its bandgap of zero value is one of its main promising peculiarities. MoS2 is efficient for electronic devices and logic due to its conductivity that can be altered. MoS2 also acts as a semiconductor.

Moreover, MoS2’s bulk form possesses an indirect bandgap which gets transformed at the nanoscale into a direct bandgap. MoS2 single layer found applications in optoelectronic devices. The 2-dimensional structure of MoS2 provides control over the material’s electrostatic nature, which is why low power electronic devices and short channel FETs are possible by MoS2.

Field Effect Transistors

The latest electronic devices have field-effect transistors as their most significant part. Semiconductor technology is evolving with time. The sizes of the transistor can be reduced to a range of a few nanometres by lithography. They have many advantages, for instance, cheap, low consumption of power, and fast switching, but with a channel size of below 14 nm. Due to the Joule heating effect, a quantum mechanical tunnelling took place between the source electrodes and drain.

Exploring the thinner gate oxides materials and thinner channels materials is important for avoiding short channel effects and fabricating nano-sized devices. 1.8 eV of the appreciable direct bandgap is exhibited by MoS2’s monolayer, making MoS2’s monolayer a suitable material to switch nanodevices.

Output and transfer characteristics

According to findings, TFT exhibits pinch-off regions and clear current saturation and works in N-channel enhancement mode. At 10V drain to source voltage (VDS), the gate voltage (VGS) was varied from -20 to 60 V to measure the transfer characteristics. TFT’s result told an efficient way of fabricating TFTs in a stable and cost-effective way.

Junyeon Kwon et al. explored conducting oxide electrodes like IZO (Indium Zinc Oxide) and ITO (Indium Tin Oxide) for showing the production of transparent multilayered MoS2. MoS2’s inherent defects led to the moderate electrical performance by TFT based on IZO and MoS2. They used the picosecond laser annealing treatment on MoS2/IZO’s contact region to enhance samples’ electrical performance.

Solid lubricants

When the requirements of the desired applications like oils and greases are not fulfilled by the liquid lubricants as some are not capable of being used in various applications because of weight, sealing problems, and environmental conditions, then solid lubricants are used. Moreover, in comparison with systems that are less weight and are based on grease lubrication, solid lubricants are cheap.

In high vacuum conditions, liquid lubricants get evaporated. When they are used in the presence of such conditions, they don’t function, rendering the device unfit too. Liquid lubricants can even decompose or oxidize at high-temperature conditions. At cryogenic temperatures, liquid lubricants either get viscous or solidify.

Liquid lubricants

Under radiation environment conditions and corrosive gas’s influence, the liquid lubricants decay. Dust or other contaminants are easily taken by the liquid lubricants, and contamination is the major problem here. Handling the components that are associated with the liquid lubricants is too difficult in applications with the requirements of long time storage because the components are just very heavy. Thus, solid lubricants efficiently deal with such problems.

Liquid lubricants fail in all aspects of space mechanisms. Antennas, rovers, telescopes, vehicles, and satellites, etc., are involved in moving systems in space. In severe environmental conditions, these systems function with little service for a long period of time. In these environmental conditions and particularly MoS2, the promising choice is solid lubricants.

In graphite contrast

Water’s vapour pressure is not needed by MoS2 for exhibiting lubrication. Slip rings, gears, ball bearings, and pointing and release mechanisms, etc., are the components in space applications that depend on MoS2 lubrications. Under humid environment’s influence, MoS2’s lubricity declines and exhibits a major challenge to its applicability in various terrestrial applications. MoS2’s sputtering with Ti includes the improvement of MoS2’s mechanical characteristics and prevents MoS2 from the humidity. This improvement in MoS2’s mechanical characteristics is significant for the operations of dry machining.

Polytetrafluoroethylene

Polytetrafluoroethylene (PTFE) is tetrafluoroethylene’s synthetic fluoropolymer possessing various applications. Teflon is the known name of the brand of the PTFE-based compositions, given by Chemours, who discovered the compound originally in 1938. It is a high-molecular-weight polymer that is made up of fluorine and carbon.

At room temperature, PTFE is a fluorocarbon solid. Polytetrafluoroethylene is hydrophobic as neither water nor the substances that contain water can wet PTFE, as the mitigated London dispersion forces are demonstrated by fluorocarbons because of fluorine’s high electronegativity. One of the lowest coefficients of friction of any solid is possessed by PTFE.

Non-stick coating

For other cookware and pans, PTFE is utilized as a non-stick coating. It is partly due to the strength of the carbon-fluorine bond that it is non-reactive. It is usually utilized in pipework and containers for corrosive and reactive chemicals. Polytetrafluoroethylene lessens the machinery’s energy consumption, wear, and friction when it is utilized as a lubricant. It is utilized commonly in surgical interventions as a graft material. It is also used commonly on the catheters as a coating as it prevents bacteria and other infectious agents from adhering themselves to the catheters and causing hospital-acquired infections.

Production

Tetrafluoroethylene’s free radical polymerization produces PTFE. n F2C=CF2 → −(F2C−CF2)n− is the net equation. Special apparatus is needed for polymerization for preventing the hot spots that may start this dangerous side reaction as tetrafluoroethylene can decompose to carbon and tetrafluoromethane explosively. Persulfate typically initiates the process that homolyzes for the generation of sulfate radicals: 2 SO4•− ⇌ [O3SO−OSO3]2−

Results

Sulfate ester groups terminate the resulting polymer, and it can be hydrolyzed for giving OH end-groups. The conduction of polymerization takes place as an emulsion in water due to PTFE being poorly soluble in all of the solvents almost. The suspensions of polymer particles are provided by this process. Surfactant like perfluorooctanesulfonic acid (PFOS) is used to alternatively conduct polymerization.

Properties

With 600 K (327 °C; 620 °F) of melting point and almost 2200 kg/m3 of density, polytetrafluoroethylene is a white solid at room temperature, and it is a thermoplastic polymer. At temperatures above 194 K (-110 F, -79C), good flexibility is maintained by it, and at temperatures lesser than or equal to 5K (-450.67 F, -268.15 C), it maintains self-lubrication, toughness, and high strength.

Like all fluorocarbons, the properties of PTFE are gained from the carbon-fluorine bond’s aggregate effect. Alkali metals and other extremely reactive metals are the only chemicals that can have an influence on these carbon-fluorine bonds. At higher temperatures, even fluorinating agents like cobalt (III) fluoride and xenon and metals like magnesium and aluminium can affect these bonds. PTFE goes through depolymerization at temperatures more than 1200-1290 F (650-700 C).

Friction coefficients

Usually, plastic’s coefficient of friction is measured against the polished steel. The coefficient of friction of PTFE is the third-lowest of any solid material that is known. Its value is 0.05 to 0.10. PTFE is the only surface that is known to which a gecko can’t stick, and that’s because of the resistance of PTFE to the Van der Waals forces. Polytetrafluoroethylene can, in fact, be utilized for preventing insects from climbing up the surfaces that are painted with that material. Insects don’t have a grip and fall off because of polytetrafluoroethylene being so slippery. For instance, polytetrafluoroethylene is used for preventing ants from climbing out of formicaria.

Superior characteristics

PTFE has remarkable thermal and chemical characteristics and is usually utilized within industries as a gasket material that needs resistance against aggressive chemicals like chemical processing or pharmaceuticals. Although it is because of its chemical inertness that no one knew PTFE to crosslink like an elastomer until the 1990s.

Thus, leading to no memory and subjection to creep. As compared to elastomers that display near-zero or zero levels of creep, the long-term performance of these seals is worse due to the propensity to creep. Belleville washers are usually utilized in critical applications for applying continuous force to PTFE gaskets, thus guaranteeing very little loss of performance over the gasket’s lifetime.

Effect of PTFE coatings

It is certain that the ingestion of PTFE doesn’t cause developmental toxicity due to its regular usage in the in vitro fertilization techniques of humans and its extreme inertness. For instance, there was a study in which various Teflon catheters were used to transfer and implant 194 human embryos inside the uterus. That study was also done by using nylon catheters for transferring and implanting human embryos inside the uterus. So, these experiments showed that when the nylon catheters were used, the mouse embryos were not able of surviving incubation within those catheters for 1 hour, but when Teflon catheters were used, no embryo was affected by the same incubation.

Dermal exposure

Exposure of dermis to polytetrafluoroethylene is safe. Usage of the polytetrafluoroethylene needles in the intravenous access is evidence of that safety. According to an international standard for medical devices’ biological evaluation, polytetrafluoroethylene is utilized as a negative control material for them too. One can find PTFE strips in razors. Due to its smoothness and softness, polytetrafluoroethylene is utilized in dermal cosmetic creams too. PTFE is broadly utilized in dental floss. PTFE is not a sensitizer or a skin irritant in humans.

Non-antigenic properties

PTFE is non-antigenic and is immune to toxicity which is proved by the evidence that PTFE is well tolerated in a broad range of surgical applications, generally including ophthalmology. Substance’s carcinogenicity should be distinguished from an inflammatory response as an inflammatory response is produced by any of the implanted foreign-body; in the surgical field, this principle is general, and it is also implemented to the most inert compounds that are PTFE. Various studies have been performed regarding the existence of some kind of immune response to PTFE surgical implants. Although there is no information of use on PTFE’s carcinogenicity provided in these studies.

Classification of PTFE

The World Health Organization International Agency classified PTFE as Group 3 for Research on Cancer (the agent is not classifiable because of its carcinogenicity to humans). It is reasonable to say that PTFE is not carcinogenic due to its extensive usage and chemical characteristics. PTFE is referred to as noncarcinogenic. It should be noted that PTFE’s monomer, tetrafluoroethylene (TFE), is for sure a human carcinogen because, as compared to PTFE, TFE is an extremely different material. At room temperature, TFE is an unstable explosive gas. No TFE residues are contained by the PTFE samples; if they were, then the stability of the PTFE won’t be as perfect as it is.

Risks of ingestion

One should address the bioaccumulation along with the material’s toxicology for analyzing the PTFE ingestion’s risk thoroughly. Other mechanisms like persorption, or paracellular transport and transcellular, can cause the uptake of the particles from the gastrointestinal tract, making the size of the particle another major parameter that needs to be considered.

Differences of MoS2 and PTFE coatings

It is because of their excellent lubricity under vacuum conditions that scientists have made molybdenum disulfide (MoS2) films for vacuum and space applications. Although, much poorer lubricating performance is displayed by pure molybdenum disulfide films under normal ambient conditions because of the film’s interaction with the ambient atmosphere’s moisture. There has been a recent increase in the interest in the utilization of the MoS2 films in the field of precision engineering, for instance, in manufacturing operations and in bearing components.

There have been efforts for enhancing the MoS2 film’ moisture resistance (mainly by surface), film-substrate system’s bulk modification and interface, including the doping of MoS2 films with numerous types of metals.

Advantages of applications

Properties of polytetrafluoroethylene (Teflon or PTFE) are beneficial for various applications. Those properties include remarkable tribological performance, low surface tension, chemical inertness, and high thermal stability. Polytetrafluoroethylene is sputtered by Liu et al. for enhancing the substrate’s tribological performance and providing the surface with hydrophobicity.

Attempts are shown in this paper for using the co-sputtering technique for doping MoS2 films with moisture-repellent polytetrafluoroethylene (PTFE), with the aim of enhancing the film’s tribological performance and lessening the sensitivity of the moisture. Various analytical and experimental approaches can be used to characterize the resultant films. For film wear-life and friction coefficient measurements, ball-on-disc sliding tests are done. For evaluation of elastic modulus and hardness, nanoindentation is done, whereas scanning electron microscopy is used for the examination of the morphology of the film.

Conclusion

An inorganic compound made up of sulfur and molybdenum is known as molybdenum disulfide (or moly). Polytetrafluoroethylene (PTFE) is tetrafluoroethylene’s synthetic fluoropolymer possessing various applications. MoS2 and PTFE are both extremely efficient and authenticated products which are highly essential for our industries as they play a pivotal role in enhancing the growth and productivity of the industries and products themselves. This is why they have a wide range of applications, and their uses are constantly increasing in the market. Nonetheless, they have their own effects and differences as they both are individual products

4 Best applications of fullerenes in the biomedical industry

Fullerene is a very common compound known as an allotrope of carbon that consists of carbon atoms that are attached through either single or double bonds. These molecules are rich in their characteristics and have potentially strong properties which enable them to work effectively. 4 best applications of fullerenes in the biomedical industry are explained in this article.

There are so many reasons which enhance the production and credibility of fullerenes. A maximum number of applications are said to be discovered in the field of medicine and are proving as an outclass representation of this molecule.

Introduction

Fullerene is a carbon allotrope consisting of carbon atoms that are either joined together by single or double bonds. This enables the formation of a partially closed or closed mesh in which five to seven atoms are fused. This molecule can be presented in various shapes and sizes namely a hollow sphere, an ellipsoid, or a tube shape. Graphene is the greatest example of this and can be found as a member of this family as it is a flat mesh that consists of regular hexagonal rings.

Closed mesh topology

Fullerenes are capable of exhibiting a closed mesh topology and are depicted by an empirical formula which is Cn in which n is known to be the number of carbon atoms that are present. Although, it is possible to have more than one isomers as the values can vary in different ways.

 

Naming

The naming system for each compound and its family is different and so is the case with fullerene as well. The family of fullerene is named after a compound known as buckminsterfullerene (C60) which is the most popular member of this family. This one is named after Buckminster Fuller. These are the closed fullerenes and can also be called buckyballs as they have a lot of similarities with the game of soccer. Likewise, the nested closed fullerenes are known as bucky onions whereas the cylindrical fullerenes are known as nanotubes or buckytubes. There is a term called fullerite which is the solid mixture of either pure or mixed fullerenes.

Polyhydroxylated fullerene (Fullerenols)/ C60

Prediction

Fullerenes were initially just predicted and no discovery of them was yet made until 1985 when they were found out in nature as well as outer space. This discovery led to the identification of an allotrope of carbon and in return added up to the already discovered allotropes of carbon. Some of the previously identified allotropes of carbon include graphite, diamond, and amorphous carbon in the form of soot and charcoal. A lot of researches have been carried out related to them to read their chemistry and have a grip on their technological applications mainly in the fields of electronics and nanotechnology.

Source of attraction

Ever since the fullerenes have been discovered in 1985, they have gained a lot of attention and attraction in various fields and specifically in the science field. Various properties of fullerenes in physical, chemical, and biological aspects have also been identified. Specifically, in the medical field, they are known to have a definite size, hydrophobic properties, and possible electronic configurations. They consist of mainly a carbon cage structure and due to the potentially strong properties, it enables them to be a therapeutic agent. Various studies have been led in the biological applications, all of which have made it evident that fullerenes are an excellent compound being utilized in the field of medicine.

Characteristics of fullerenes

There are various characteristics of fullerene which are the basis of this compound and are the key functionalizing aspect that enhances the growth and production of fullerenes. The entire family of fullerene and most specifically C60 has a very appealing nature and is thus referred to as the best compounds to exhibit their physical and electrochemical properties. As discussed earlier, fullerene has a hydrophobic nature and this enables it to fit itself in HIV protease to stop the movement of substrates towards the site of the enzyme. There are several ways in which fullerene can be characterized mainly in the form of exposure to light and it also works as a carrier for the entire drug delivery systems and gene.

Properties

Fullerene has a lot of properties all of which when combined can form a compound that is highly effective in maintaining the quality of it and then add up to its market value as well. A few of the most important properties of fullerene are known to be the building blocks of this product.

Topology

Topology is a mathematical study of certain products whose properties are dependent upon the structural variations that come along within a product. The prominent term is Schlegel diagrams which help in the identification of 3D structures of fullerenes having closed shells because the 2D technology is not much applicable to it. This diagram helps in the identification of convex polyhedrons. This is a basic approach of fullerene to study the properties and characteristics so that a better approach can be adopted for the proper working and functioning of fullerenes.

Closed fullerene

The most common type of fullerene is a closed fullerene which consists of a sphere-like shell having cycles of both, either pentagons or heptagons. When the shell’s faces have 5 to 6 sides then a formula is followed by them which is known as Euler’s polyhedron formula. The formula is stated as V-E+F=2. Here V represents vertices, E represents edges and F represents faces. Everything is followed in the same pattern even when a fullerene exists with a heptagonal shape. Different types of fullerenes can have different kinds of shapes, depending upon the boding that they possess. Similarly, their functionalization varies from one another as each product contains its specifications and then works accordingly.

Bonding

Every carbon atom consists of either a single or a double covalent bond due to the connectivity level that it shares with the neighboring atoms. There is always a mixture of these bonds present. However, a technique known as Raman spectroscopy is the most common one through which the bonding state can be identified and then worked upon. Others include IR spectroscopy and X-ray spectroscopy.

Aromaticity

Buckminsterfullerene is not capable of possessing the feature of super-aromaticity which means the localization of hexagonal rings over the molecules does not take place. Several types of research have also been conducted in this regard to enhance the reactivity of fullerenes.

Spherical fullerene

Spherical fullerene is another different shaped type of fullerene in which n acts as the number of carbon atoms that are free to perform any delocalization. They are allowed to try delocalizing over the entire molecule. A certain series of the number of carbon atoms is provided for this arrangement where the stable shell must be equivalent to n = 2, 8, 18, 32, 50, 72, 98, 128, etc. The formula of 2(N + 1)2 is applied to this rule which is known as Huckel’s rule. Quantum chemical modeling is the case that is used here for showing the types of spherical currents being found in the cations. These are rather very strong and diamagnetic.

Result

C60 becomes able to attract two electrons and then becomes an anion. This maybe be caused while a loose metallic bond is being formed either partially or completely.

Functionalized fullerenes as drug-delivery nanoparticles

PEBs which are known as paclitaxel embedded buckysomes are a type of amphiphilic fullerene while consisting of nanostructures that are approximately 100 to 200 nm. They have hydrophobic pockets inside them which contain the anti-cancer drug paclitaxel. The US FDA has also approved of them as these are the drugs that protect a human body from some life-threatening conditions, for example, breast cancer. This water-soluble fullerene and its derivatives protect the person from any side effects and discomforts that come along.

Advantageous approach

This is a thoroughly advantageous approach because it helps a person in fighting the disease and certainly improves the circulation of blood, as well as the anti-cancer drugs, cause various kinds of side effects one of which is poor blood circulation. However, the size of these PEBs is very small equivalent to 200 nm so that RES uptake can be avoided at all costs.

Production of the lipophilic slow-release system

As discussed earlier that fullerene is capable of producing an ideal lipophilic system so it helps in creating several drugs which can be used as a single dose naming them as the drug cocktails. This was discovered by Zakharian and colleagues. This is the most common practice for the therapy of lung cancer. The conjugates that are discovered shall have a size range of 120 to 145 nm and it should be considered important that the size is not varying with concentration. However, this conjugate comes with a half-life of release of 80 minutes in the case of bovine plasma.

Transfection vectors

Other than giving out drug molecules, fullerenes also work as the transfection vectors for the deliverance of exogenous DNA so that they can be worked up to check for mediate gene transfer. This is a highly beneficial technique in the process of gene therapy. Though the cytotoxicity levels are high in the first generation fullerene transfection their promising nature in the case of transfection subsides it. However, Sitharaman and colleagues were able to discover a new class of fullerene and its derivatives which are helpful in the transportation of DNA across the cell and gene expression as well.

Transfection efficiency

However, transfection efficiency is brought along only with the help of fullerene and its derivatives. It is capable of possessing the properties and characteristics which are essential in carrying out this process. A lot of other researches as well were carried out in this regard all proved that gadofullerne has an approach in the field of diagnosis and therapy.

Reactive oxygen species (ROS) quenching by functionalized fullerenes

Krusic and colleagues are known to figure out all the potentials of fullerene for scavenging reactive oxygen species. This has initiated and increased the interest of marketers to start using fullerene as an antioxidant. It is important to watch out for all the important steps that are necessary for carrying out this process. Other than that carboxy fullerenes are also used as neuroprotective agents.

Antioxidant compounds

It was suggested in early phases that C60 and its derivatives are capable of having antioxidant compounds which are highly beneficial in the biological systems. Carboxyfullerne is the most important one among all as it occupies excellent antioxidant compounds. The most prominent function of this is that it protects from neuronal apoptosis which consists of two types as well. It works as a mediator which inhibits the necrotic and apoptotic neuronal deaths as a result of which protection to the human body can be provided at a larger level. Their use in drugs is also proving to be highly beneficial as neuroprotective drugs are based on this mechanism.

Influence of size

Along with that, the size of fullerene is also very important as it influences the processes that are going on. An experiment was led out which depicted that fullerenes are capable of reducing cytotoxicity, damage to the mitochondria, and formation of free radicals as human lung carcinoma cell line and capillary endothelial cell line of a rat’s brain was used in this experiment. As a result, it was predicted that in comparison to the other two derivatives of fullerene, the gadofullerene and its derivatives help protect from any injury to the mitochondria. It was then concluded that fullerene and its derivatives are capable of scavenging all the related ROS.

Iron-induced lipid peroxidation

Another study was presented by Lin and colleagues that carboxy fullerenes consist of anti-oxidative properties so these are also capable of repressing iron-induced lipid peroxidation. As discussed earlier that carboxy fullerenes provide neuroprotection so in this case as well they help in the degeneration of the nigrostriatal dopaminergic system. A lot of other researches were also carried out which confirmed the antioxidative properties of fullerene and the potential that I hold as a free radical scavenger.

Process of apoptosis

Fullerenes are highly beneficial for the inhibition of apoptosis which was discovered by Monti and colleagues as carboxy fullerenes is a type of fullerene which helps protect blood cells from going through apoptosis along with the involvement of mitochondrial membrane. This is known to be carried at the earliest stage of apoptosis. This entire activity is performed by buckminsterfullerenes for the protection of the immune system and the mitochondria involved.

Fullerenes as photosensitizers

Fullerene has excellent biomedical applications in the case of photosensitizers as it brings out the photoexcitation state of fullerenes. Fullerene tends to transform into a photoexcitation state even from the ground state through the process of photo-irradiation. This process enables the life expectancy of C60 as a result of which it can be incorporated in photosensitizers for better functionalization. In this process, O2 is converted into singlet oxygen which is considered a highly cytotoxic species. As a result, fullerene in its excited state can work best as it becomes reduced due to the presence of biological reducing agents example of which is guanosin. Fullerenes play a vital role in the conversion reactions, enabling the transfer of electrons to go correctly and effectively as a result of which fullerenes’ potency increases.

Use of polyethylene glycol

PEG known as polyethylene glycol is a conjugated type of fullerene which was initially procured by Gd+3 ions for a process called photodynamic therapy while combining with the magnetic resonance imaging commonly known as MRI. Researchers have collected a lot of data in the same regard because this type of fullerene is capable of making these processes a smooth task and provides a great deal of help. An experiment on mice regarding the same was conducted as well which concluded that indeed C60-PEG plays as a derivative that possesses diagnostic and therapeutic, functions.

Fullerenes for Medical Therapeutics and Diagnostics

Being the best compound to be used in the medical field, it sure brings a lot of benefits to medical therapeutics and diagnostics. Fullerenes have been found out to be great antioxidants along with being radical scavengers. They possess extremely good anti-inflammatory properties which enables them to protect the body from any toxins from various diseases. A few of these diseases include:

1) Fullerenes for Allergies

Mast cells are the ones that can be identified in body tissues of a human body and these are the ones that initiate allergic responses in a human body. The allergies are triggered when one comes in contact with any sort of allergens and in that case the cells reveal mediators which are responsible for these triggers. Fullerenes and their derivatives then come around to have control over these allergens to protect the human body from allergic reactions. They are capable of protecting the human body before, during, and after any allergy gets triggered. These help the ongoing reactions to stop before their devastating outspread.

2) Fullerenes for Asthma

Asthma is one of the most common diseases nowadays and the greatest percentage of it lies on mast cells. The main trigger of asthma is different types of allergens and allergy-causing organisms. Fullerenes are being used and studied to identify ways in which they can be found helpful to protect from allergic reactions being generated in the human lungs.

3) Fullerenes for Arthritis

The building blocks of arthritis are mast cells and in that case, fullerenes are being discovered and utilized to present how the growth of mast cells can be inhibited for the prevention of arthritis.

4) Medical Diagnostics

Another one of the major applications of fullerene is the field of medical diagnostics. A lot of procedures go by every day to diagnose diseases that are either known to man or not known. To keep this method free from any toxicity, advancements and adaptations are being applied at every level. For example, in the case of treating kidney diseases, steps are taken in which Gd is to be transformed into chelate so that it can stay in the body for a small period, and then it can eliminate from the body via renal elimination. This can end up releasing toxicity in the body in the form of toxic substances because Gd and chelate start separating at one point. All of this can be prevented by an agent-based upon Trimetashere which prevents the toxic substances from separating no matter for how long they are in the solution.

MRI

MRIs are physiological tests performed on people who are suspected of any disease or are supposed to go through some procedure. Though there is still a need to bring improvement in the performance of MRI. This can be done through making an increase in the relaxivity by the use of Trimetaspheres as this enhances the performance ability of MRI. This is indeed a very effective way to bring change and advancement in this said field.

Coronary Artery Disease

Coronary artery disease is one such disease that has been thoroughly studied due to Trimetasphere derivatives. This compound has a high potential to be dealt with potentially strong and stable components which are capable of dealing with the plaque that builds up in the blood vessels of humans due to this disease. This entire process helps eradicate the risk and severity of heart attack as it provides awareness and information regarding the disease itself and the precautionary measures that can be dealt with through knowledge. The involvement of fullerene enables all these processes to go by smoothly and swiftly.

Conclusion

Fullerene is an allotrope of carbon is known as one of the best compounds that are being used in various industries but specifically in the biomedical industry. There are several industries in which the applications of fullerenes can be expressed but the main and most important ones can be found in the biomedical industry. Fullerene is working as an excellent compound for enhancing the credibility of the biomedical industry.

​Uses of Graphene Sheet Films

Graphene is a hexagonal lattice of carbon-containing single layers. It is an excellent and one of the most exceptional forms of carbon. There are several forms of graphene and graphene sheet films are one of those excellent forms as they contribute a lot in building up the industries and economy. They have excellent chemical and physical properties which are essential in carrying out all their uses.

All the applications of graphene sheet films are highly authentic in their nature and are considered as an excellent source of building up the industries and the economy of the states. Nonetheless, graphene is an excellent product and all the forms of graphene are excellent in their nature too due to the commendable properties that graphene as an individual holds.

Introduction

Carbon atoms single layer that are bonded in a hexagonal honeycomb lattice leads to a structure possessing numerous required characteristics that seek the attention of various applications is known as graphene. High thermal conductivity and high charge carrier mobility are among the unique characteristics of graphene, and its large surface area makes graphene suitable for catalysis or sensing applications.

Although, effective usage of graphene in various technological applications is dependent on the production of the suitable type of graphene-based material varying from few-layer graphene sheets and large area single sheets to laminate films sintered from various micro- or nano-meter-sized graphene platelets.

Quality

Vacuum-based deposition technologies like CVD (chemical vapor deposition) can be used to successfully produce high-quality few- and single-layer graphene of -10 layers thickness. A carrier gas made up of CH4 that under high temperatures, forms a reaction with the surface for promoting graphene growth are capable of being used to grow CVD graphene on the metal substrates that are lattice-matched to the graphene lattice-like Cu and Ni.

CVD is used by both substrate types for fabricating few- and single-layer graphene of high quality, however, the substrate material determines the growth method as it varies. Remarkable electrical characteristics are seen by the graphene that’s grown by the CVD methods and they can nearly almost the graphene sheet’s estimated theoretical performance.

Graphene Sheet

Outcomes

Although, graphene of high quality that’s produced by CVD is expensive to produce, and it shows sensitivity towards defects and contamination, resulting in it being difficult for being utilized efficiently in various device applications. Graphene should be transferred to other substrates like Si/SiO2 as the substrates that are utilized in the growth of graphene are not suitable for the architectures of all devices. A solution-based method using a sacrificial polymer like a cross-linked polymer or poly-methyl-methacrylate (PMMA) is commonly used to accomplish it but it can introduce contamination and defects.

GO/rGO’s PREPARATION/SYNTHESIS

Graphite oxide is different as graphite is a 3-D carbon-based material that is made up of millions of layers of graphene. The oxygenated functionalities are introduced into the structure of graphite when strong oxidizing agents oxidize graphite, which didn’t only expand the separation of the layers but made the material hydrophilic too which means that they are dispersible in water. This characteristic allows graphite oxide’s exfoliation into the water by utilizing sonication, and finally forming few-layers graphene or single-layer graphene.

Hummers first reported a method on which many of the modern procedures for GO’s synthesis are based. In that method, potassium permanganate’s solution oxidizes graphite in sulfuric acid. General usage of hydrazine is for GO’s reduction.

Graphene oxide’s Functionalization

Although it’s due to these problems that hydrazine is extremely toxic and is capable of potentially functionalizing graphite oxide with the nitrogen heteroatoms, alternatives to hydrazine like HI, ascorbic acid, and NaBH4, among others, have been utilized for GO’s reduction. Reduction of GO is possible in an aqueous solution or a thin film. This oxidation has GO as its effective by-product as when graphite forms a reaction with the oxidizing agents, the interplanar spacing between graphite’s layers is increased. Then, the totally oxidized compound can be dispersed in water and other base solutions, thus producing GO. Chemically, GO and graphite oxide are the same but they are very different when it comes to the structure.

The interplanar spacing between the compound’s individual atomic layers is the major difference between GO and graphite oxide, and its reason is water intercalation. The sp2 bonding network also disrupts because of this increased spacing that’s caused by the process of oxidation, meaning that both the GO and graphite oxide are usually known as electrical insulators. Despite being a poor conductor, GO’s treatment with chemical reduction, heat, or light can restore most of the characteristics of the famed pristine Graphene. Few methods are possible for turning graphite oxide into GO.

Most common approaches

Some of the most usual approaches are utilizing stirring, sonication, or both in combination. Sonication forms a broad range of sizes of graphene platelets. It can damage the Graphene flakes thus lessening them in the size of the surface from microns to nanometers. Sonication has been very successful in the exfoliation of graphene and it can be an extremely time-efficient method to exfoliate graphite oxide.

The number of layers is the major difference between GO and graphite oxide. However in GO dispersion, graphite oxide is a multilayer system, one can find a monolayer of flakes and some layers of flakes. Producing rGO by reducing GO is a very vital process as it makes a large influence on the produced-rGO’s quality. Thus, determining how close rGO will be the same in structure to the pristine graphene.

Large scale operations

It is due to comparative ease in the production of enough qualities of graphene with the required quality levels that rGO is the most obvious solution in large-scale solutions where scientific engineers want to use graphene in large quantities for industrial applications like energy storage. The reduction can be attained in various ways, however, all of those ways are based on electrochemical, thermal, or chemical means. Some methods can form extremely high-quality rGO, same as pristine graphene, but their performance can be time-consuming or complex.

Thermally reducing GO

At 1000 or more temperatures, thermally reducing GO forms rGO that possesses an extremely high surface area, similar to the surface area of pristine graphene according to findings. The graphene platelet’s structure gets damaged by the heating process as the carbon dioxide is released and the pressure builds.

Characteristics of rGO and GO

GO has many benefits and one of them is its easy dispersion in the organic solvents and water, along with various matrixes due to the oxygen functionalities’ presence. When trying to enhance the mechanical and electrical characteristics of theirs, or when mixing the material with polymer matrixes or ceramic, this stays an extremely major characteristic. Although, when it comes to electrical conductivity, due to disruption of its sp2 bonding networks, GO Is usually known as an electrical insulator.

Electrical conductivity

GO’s reduction should be achieved for recovering the electrical conductivity and the honeycomb hexagonal lattice. It should be known that the attained rGO would be more difficult to disperse once most oxygen groups are removed, and that’s due to its tendency of creating aggregates. GO’s characteristics can be fundamentally changed by GO’s functionalization. The chemically modified graphene that is produced then has the potential to be adaptable for various applications. GO can be functionalized in various ways, it is the desired application that determines its way of functionalization.

Optoelectronics

It is possible for biodevices, optoelectronics, or as a drug-delivery material to substitute amines for graphene’s organic covalent functionalization for increasing chemically modified graphene’s dispersibility in the organic solvents. According to findings, fullerene-functionalized secondary amines and porphyrin-functionalized primary amines can attach themselves to GO platelets, thus increasing nonlinear optical performance.

Significantly, we develop a process of oxidation and reduction that can separate the individual layers of carbon and isolate them then while causing no modification in their structure to make GO usable as an intermediary in the production of a few layers or monolayer graphene sheets. Completing the production of graphene sheets of similar quality like mechanical exfoliation but on a bigger scale has been very difficult for scientists. Until now, GO’s chemical reduction is the most appropriate way to mass-produce graphene but still, its production is a difficult task. Graphene is expected to become more broadly utilized in industrial and commercial applications once they overcome this issue.

Graphene thin film fabrication

Device applications have a great interest in studying Graphene’s fundamental physics and the usage of vacuum techniques for the fabrication of high-quality single-layer graphene’s large area sheets. Cu and Ni are the most usually utilized metal substrates as they have a crystal structure with similarly matching lattice spacing to graphene. Ni has a lattice structure reminiscent of graphene’s hexagonal lattice with similar lattice constants, making Ni extremely ideal for graphene growth. First, graphene is fabricated on a polycrystalline Ni substrate that is annealed at 800-1000 C of high temperature in an Ar/H2 atmosphere for increasing the size of the grains.

Polycrystalline substrate

As compared to a single crystal, the cost of a polycrystalline substrate is lower, but it possesses grain boundaries and they restrict graphene grain’s maximum size. Then, the heated Ni substrate is made to contact with an H2/CH4 gas mixture and on contact, carbon atoms dissolve into the Ni film as the hydrocarbons decompose, thus producing a solid solution. Using argon gas to cool the sample causes the atoms of carbon to diffuse out from the Ni-C solid solution and precipitate on the surface of Ni in graphene films’ form.

Same carrier gases are involved in the process in which Cu is used as a substrate. Although, at increased temperature, the solubility of carbon is much lower in Cu whereas the solubility of Ni is more. Instead of dissolving, hydrocarbons decompose on Cu’s surface into a layer of Graphene as Cu is well lattice-matched to graphene too. Multilayer graphene can be easily produced by this technique by simply enabling the proceeding of the reaction for a longer time so that a Graphene multilayer can be built. CVD Graphene on Ni or Cu can be transferred to other substrates for becoming a device architecture’s part or being used to process further with chemical functionalization or metal nanoparticles.

Advantageous for applications

Applications needing a few- or single-layer Graphene can get various advantages from this procedure. CVD graphene is ideally suitable for being utilized as a potential alternative to more expensive transparent conducting applications like ITO (indium tin oxide) in solar cell devices as they are extremely conductive (100–1000 Ω/square) and transparent (98% transparency to visible light) which makes them a perfect material. Although, the requirement of a single-crystal, large substrate restricts the single-grain graphene sheet’s ultimate size.

CVD Graphene is integrated into devices by using the solution transfer process and it limits CVD graphene’s usage by introducing a PMMA residue and defects that are difficult enough to remove. Such factors restrict the defect-free graphene grain’s ultimate size that is attained by utilizing a process of fabrication of CVD graphene.

Graphene Sheet Films

Graphene and graphene sheet films are the 2-D exfoliated graphite with remarkable and excellent chemical and physical characteristics. Graphene sheets are technically and specifically made up of carbon atoms single layer with carbon rings arranged into a hexagonal configuration that’s the same as the honeycomb lattice. Graphite and graphene sheet films possess a similar atomic structure as graphite’s thousand of these single layers stacked and bound to one another by utilizing Van Der Waals forces. Graphene possesses 2 or more layers with incommensurate adjacent Graphene sheets.

Monolayer graphene films

Free monolayer graphene films retain Graphene’s ultra-high thermal conductivity characteristic with the thermal conductivity value as much as 3000 W/m.K. Lower density and remarkable flexibility are maintained by them whereas the most usually utilized metals for the dissipation of heat can’t maintain as such. Different macro-scale morphology yet same micro-scale morphology were seen to be possessed by the graphene sheet films that were made by various advised methods because of the annealing at higher temperatures. Shiny metallic color with 7.5 micrometers of thickness is possessed by graphene sheet films. Their color is shiny metallic.

Graphene Sheet Films Characteristics

Graphene is the center of attention of many scientists because of its excellent structure and remarkable characteristics, especially keeping in mind the one-atom-thick planar sheet with carbon-carbon binding’s sp2 hybridization. Single-layer graphene sheets with a single-layer nature have remarkable electronic characteristics because of the 2-D structure of the graphene sheets. Graphene sheet films’ electronic characteristics are because of their features like specific and ballistic electron transport, the half-integer quantum Hall effect, and bandgap width.

Factors like the number of carbon rings along graphene sheets length or its minimum length, and the size of the graphene sheets determine the characteristics of graphene for instance its electrical conductivity and Young’s Modulus. In order to fit into criteria 1 of nanoscale homogenization, the length of the graphene sheets should be very long so it could be favorable enough. The major electric and electronic characteristics among fullerenes and carbon nanotubes are originated from graphene sheets.

Preparation and Synthesis of Graphene Sheet Films

Various kinds of methods are being utilized right now for graphene sheet film’s preparation and synthesis namely micromechanical cleavage, graphene oxide reduction, chemical vapor deposition (CVD), direct ultrasound sonication, scotch tape, vacuum thermal annealing, chemical, and thermal exfoliation, with each of the method possessing its benefits and losses along with their applicability-based compatibilities. Although, applying these methods to mass-produce industrial scales and purposes is kind of not so common. Graphite is oxidized to attain graphene oxide and it is utilized for achieving exfoliated 2-dimensional graphene sheet films.

Expandable graphite’s Exfoliation

In another method, expandable graphene is exfoliated at more than 1000 °C for 60 seconds to prepare single-layer graphene sheet films. NaCl is applied in the next step for grinding graphite for three minutes or some for exfoliating it and it leads to a homogenous grayish mixture. Then, NaCl’s aqueous dissolution collects the exfoliated graphite and treats it for 24 hours at room temperature with oleum. The end sample is ultra-sonicated for five minutes in N, N’-dimethylformamide. Graphene sheet films are Generally made through carbon evaporation on an organic precursor for instance the controlled deposition and Polymethyl methacrylate (PMMA) on a substrate. Direct evaporation method, vacuum filtration method, and other assembling methods are the other methods that should be mentioned too.

Graphene Sheet Films application

There has been a massive increase in the interest in graphene sheet films for their application in a broad range and practically because of graphene sheet films’ huge contribution to numerous studies and thermal management areas, namely thermal interface materials and heat dissipation materials with really promising results. For example, there has been a demonstration of the graphene sheet film’s thermal management capabilities by using them in 7w high-bright LEDs with the recorded lower temperatures as hot spots, whereas in the graphene sheet’s absence, an increase in the temperature was seen.

Due to the lightweight, stretchable, and ultra-flexible graphene sheet films application cloth, there is a fast increase in the temperature and then a consequently fast temperature decrease in 5 minutes to the room temperature. Various applications like antibody-functionalized graphene sheets for diagnostic devices and mammalian and microbial detection as potential agents have been found by the graphene sheet films because of graphene sheet films’ remarkable structural, mechanical, and electrical features, large surface area per unit volume, and thermal characteristics.

Unique transparency

In the development of biosensors, graphene sheet films’ excellent transparency makes graphene sheet films the perfect candidates. In doing so, sensor-coated graphene can function as an uncoated sensor while they are mechanically and chemically protected and they can make as much contact in aqueous solutions.

We can solve the bottleneck’s problem for nanopore-based DNA sequences with a single molecule by integrating 0.4 nm or less of graphene sheets into a nanopore. Their application is in the fabrication of condoms and elastic composite materials too. Brain tissue is viewed in a recent application by using implantable sensors based on transparent and flexible graphene with 90% of optical transparency.

Transformation into a liquid crystal

One can transform graphene sheet films into liquid crystal droplets by the placement of droplets in a changing pH solution. In this way, the structure of the graphene droplets changes while the application of a magnetic field, making it a drug carrier. Detection of disease is graphene sheet films’ another application as there are demonstrations of it that when graphene is exposed to some of the specific disease markers, graphene changes shape.

Graphene sheets are also known as flying carpets in medical applications for functioning as a drug delivery platform for delivering two anticancer drugs to the lung tumor cells. Here, doxorubicin drug is encapsulated in the graphene sheets and when it is reached to tumor cells, it is released

Waterproof transistor designing

Graphene sheets are used in different applications in designing and fabrication of the waterproof transistor with graphene sheets being grown on metal. A digital switch can be made with a 105 ratio at 0.5 V of turn-on voltage by using boron nitride nanotubes for the perforation of a graphene sheet. In short, one can use graphene sheet films as conductive ink, spintronics, organic electronics, graphene quantum dots, Hall Effect sensors, optoelectronics, frequency multiplier, and transparent conducting electrodes.

Inheritances

Due to mother graphite, graphene sheet films possess remarkable electronic and thermal characteristics, remarkable conductivity, and they have found applications because of their such intensified characteristics as biosensing platforms, semiconductors, and transistors, and in cancer therapy and drug delivery. Graphene is at the center of attention of numerous applications and research due to various preparation and synthesis method along with graphite’s huge source as the raw material.

Conclusion

Graphene sheet films are being used at a great scale nowadays as they possess properties that are authentic in their nature and promote the credibility of the product. Their production as well has increased massively over the past years which has eventually increased their applications as well. However, graphene sheet films are excellent products that are proving their originality by contributing a lot in the form of various applications and uses.

​Explained: Silicon batteries and Applications

Lithium-silicon battery use lithium ions and silicon-based anode as the charge carriers. A huge specific capacity is generally possessed by silicon-based materials. Silicon is possessed in small quantities by the commercial battery anodes, and it slightly boosts their performance. Due to its remarkably high specific capacity, there have been extensive studies on silicon as a material of anode for lithium-ion batteries (LIB).

LIBs have different applications among various industries because of their stable performance, comparatively high energy density, and environmental benignity. LiBs market size can also surpass the market size of the portable electronics in electric vehicles case. There has been a great demand for batteries with enhanced safety, lower cost, higher power, and energy density in this regard. There has been the adoption of lithium-ion batteries (LIBs) for portable electronic devices as the major energy storage technology and they are also being taken into consideration for various markets like grid-scale energy storage.

 

Introduction

A substrate of lithium-ion battery technology is known by the name lithium-silicon battery and they use lithium ions and silicon-based anode as the charge carriers. A huge specific capacity is generally possessed by silicon-based materials, for instance for pristine silicon, it’s 3600 mAh/g, as compared to graphite that has 372 mAh/g as its maximum theoretical capacity for LiC6 the fully lithiated state. When lithium is inserted, the large volume change of silicon (almost 400 percent based on crystallographic densities) is one of the major complications and the high reactivity in the charged state to this type of anode’s commercialization is another major complication.

Silicon is possessed in small quantities by the commercial battery anodes, and it slightly boosts their performance. The nearly held trade secret is the amount, as in 2018 it was limited to 10% of the anode. Cell configurations are also included in the lithium-silicon batteries where Si at low voltage may store lithium through a displacement reaction as Si is in compounds, including silicon nitride, silicon monoxide, or silicon oxy carbide.

Due to its remarkably high specific capacity, there have been extensive studies on silicon as a material of anode for lithium-ion batteries (LIB). Although, during the discharge and charge process, usually the silicon-based anode materials go through a large volume change resulting in continuous side reactions, loss of electric contact, and silicon’s subsequent pulverization. The poor life cycle is caused by these transformations and they cause a hindrance in silicon’s broad commercialization for LiBs. There have been progressive studies and understanding of the interphase reaction mechanisms, and the lithiation and de-lithiation behaviors.

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How to use mesocarbon microbeads graphite micron powders in the battery industry, its properties, and potential use

In comparison to commercial carbon-based anodes

As compared to commercial carbon-based anodes, there have been reports of numerous nanostructured silicon anodes that possess both excellent cycle life and specific capacity. Although, there are some practical issues regarding nanostructured silicon that can’t be ignored and if it is going to be utilized broadly in commercial LIBs then it should be addressed. Major affective work on the silicon-based anodes is outlined in this review along with the latest research directions in this field, particularly, silicon architecture’s engineering, silicon-based composite’s construction, and other performance-improvement studies for instance binders and electrolytes.

There is special stress on the burgeoning research efforts in developing fuel-cell silicon-based LIBs and practical silicon electrodes, which are key to silicon anode’s successful commercialization, and next-generation high energy density LIB’s large-scale deployment. Recently, there has been high dependence of mankind on non-renewable energy that has resulted in an increase in the number of concerns on human health, climate, and environment.

Significance

Right now, one of the major and interesting topics around the globe is the research and development of clean energy and it is seeking more and more attention still. Over the world, there has been an increase in the market size of clean energy from wind and solar, resulting in an extremely strong requirement for extremely efficient energy conversion and storage devices for clean energies’ broad utilization. Huge efforts on the other hand have also been devoted to vehicle electrification for lessening petroleum’s reliance on us, while there are the correspondingly appropriate energy storages devices still under probe. There has been the adoption of lithium-ion batteries (LIBs) for portable electronic devices as the major energy storage technology and they are also being taken into consideration for various markets like grid-scale energy storage.

Applications

Welcome to the Era of Supercharged Lithium-Silicon Batteries | WIRED

LIBs have different applications among various industries because of their stable performance, comparatively high energy density, and environmental benignity. LiBs market size can also surpass the market size of the portable electronics in electric vehicles case. Although due to impractical driving ranges, most of the EVs are not still competent enough by now for replacing traditional vehicle due to impractical driving ranges. The battery’s energy density/size determines the range from a single charge. When the integrated battery’s size increases, it also increases the whole electric vehicle’s mass and EV’s cost, lessening the range. An optimization problem is introduced because of this dependence loop between the total vehicle mass, battery size, driving range, and cost, and the EV’s system design completely determines it as it strongly depends on it. The presence of EVs with near practical ranges can be seen in the market but the large battery pack’s high cost typically makes them too expensive.

There has been a great demand for batteries with enhanced safety, lower cost, higher power, and energy density in this regard. USABC set a long-term goal for addressing this issue. According to that goal, the LiB pack system’s energy density should reach 500 Wh L -1 or 235 Wh kg-1 at a discharge rate of 1/3 C (1/3 C discharge rate refers to a battery that one can completely discharge in 3 hours), along with the need of calendar life of 15 years and up to 1000 cycles.

Silicon-graphite composite electrodes

Yoshio first reported the silicon-carbon composite anodes in 2002. According to the studies of these composite materials, the capacities are the two end member’s weighted average (silicon and graphite). On cycling, Silicon particle’s electronic isolation takes place with the capacity falling off to the graphite component’s capacity. Alternative synthetic morphologies or methodologies are used for tempering this effect and they can be made for helping in maintaining contact with the current collector and there have been identifications of it in studies and they involve grown silicon nanowires and alloy formation is used to chemically bind them to the metal current collector.

In 2014, Amprius used a silicon nanowire-graphite composite electrode to produce the sample production of batteries. In 2014, many hundred thousands of these batteries were claimed to be sold by the same company. A method of the encapsulation of silicon microparticles in a graphene sheet was presented by Stanford University researchers in 2016. The fractured particles are confined by that method and that also functions as a stable solid electrolyte interphase layer. 3,300 mAh/g of energy density was reached by these microparticles. Elon Musk, the founder of Tesla, claimed in 2015 that the range of the car can be increased by 6% by using silicon in Model S batteries.

In 2018, consumer-electronics companies, car companies, and battery manufacturers took products by startups Sila Nanotechnologies, Group14 Technologies, Enevate, Enovix, Global Graphene Group, and others under tests. Battery suppliers, Amperez Technology, and BMW are included in Sila clients for companies including Samsung and Apple. It is planned by BMW to incorporate Sila technology in 2023 to enhance the battery-pack capacity by ten to fifteen percent. Enovix was the first company until now to transport finished silicon anode batteries to the end customers. SCC55™, a silicon-carbon composite is patented by Group 14 technologies that allow 50% more in completely lithiated volumetric energy density as compared to the graphite that’s been utilized in the conventional lithium-ion battery anodes.

SK materials, Showa Denko, and Amperex Technology Limited have backed Group 14. Tesla showed on September 22, 2020, about its plans to increase the amounts of silicon gradually in its future batteries, specifically focusing on the anodes. Tesla plans to use an ion-permeable elastic coating for encapsulating silicon particles. The silicon-swelling concern is accommodated in this way, thus enabling the required increase in the battery capacity to be attained. This charge doesn’t cause an impact on the overall battery life expectancy. Confirming stepwise changes and Enabling testing were the reasons for the gradual and not sudden increases in the usage of silicon.

Specific capacity

3600 mAh/g of theoretical specific capacity is possessed by a crystalline silicon anode, which is almost 10 times more than that of the usually utilized graphite anodes (restricted to 372 mAh/g). In its fully lithiated state (Li3.75Si), each atom of silicon can bind up to 3.75 lithium atoms (Li3.75Si), whereas for the fully lithiated graphite (LiC6), it’s one lithium atom per 6 carbon atoms.

Silicon swelling

As the silicon atoms go through lithiation (accommodates lithium ions), the lattice distance between the silicon atoms multiplies, reaching 320 percent of the original volume. Large anisotropic stress takes place due to the expansion within the electrode materials, therefore causing a fracture and crumbling in the material of the electrode, and detaching from the current collector.

In less than 10 discharge-charge cycles, most of the capacity is lost by the prototypical lithium-silicon batteries. On lithiation, major volume expansion is important for the success of the silicon anodes as it also gives a solution for the stability and capacity issues that are posed. There have been a huge number of investigations on silicon nanostructures as a potential solution because the contraction characteristics and volume expansion of nanoparticles are extremely different from that of the bulk. As compared to the bulk silicon particles, they possess a higher percentage of the surface atoms.

Coatings, encasement, or other methods, are used to control the increased reactivity and limit surface—electrolyte contact. Researchers have identified one method in which they suggested utilizing silicon nanowires on a conductive substrate for an anode and found that direct current pathways are created by the nanowire morphology for helping an increase in the power density and the change in the volume decreases disruption. Although still a fading problem can be posed by nanowires large volume change. The potential of silicon nanoparticles was examined in the other studies. As compared to the other silicon electrodes, anodes utilizing silicon nanoparticles offer much more mechanical stability over cycling and they may overcome the scale and price barriers of the nanowire batteries. These anodes typically add a binder for improved mechanical stability and carbon as a conductive additive. Although even upon lithiation, the issue of large volume expansion is not fully solved by this geometry, therefore exposing the battery to improved risk of capacity loss from the inaccessible nanoparticles after cycle-induced stress and cracking.

Approach of nanoparticles

Utilizing a conducting polymers matrix as both the polymer electrolyte and the binder for the nanoparticle batteries is another nanoparticle approach. A hydrogel network and a 3-dimensional conducting polymer were examined in one study for encasing and allowing for ionic transport for the electrochemically active silicon nanoparticles. After 5,000 cycles, with over 90 percent of capacity retention, the framework led to a marked enhancement in the stability of the electrode. Slurry coating techniques are utilized and are some of the other methods for accomplishing similar outcomes, which are in line with currently utilized electrode creation methodologies. Zhang et al. used 2-dimensional, covalently bound silicon-carbon hybrids in a recent study for reducing stabilize capacity and volume change.

Charged Silicon Reactivity

Other than the well-recognized problems associated with the large volume expansion, for instance, cracking the SEI layer, there is another issue that involves the charged material’s reactivity. Lithium silicide is charged silicon. The salt-like structure of lithium silicide is made from a combination of lithium cations and silicon (-4) Zintl anions. There is a high reduction of these silicide anions and they exhibit high reactivity with the electrolyte components, solvent’s reduction locally compensated the charge.

An in-situ coating synthesis method has been identified by Han et al. in his recent work and that method eliminates the surface’s redox activity and restricts the reactions that can occur with the solvents. However there is no influence of it on the issues that are associated with the volume expansion, Mg cation based coating are shown to improve the capacity and cycle life considerably in a manner same as the film producing additive fluoroethylene carbonate (FEC).

Solid electrolyte interphase layer

Lithium compounds are formed on the surface of the anode by the decomposition of the electrolyte starting from the lithium-ion battery operation’s first cycle, therefore forming a layer that is known as the solid-electrolyte interphase (SEI). The SEI layer is due to the anode’s reduction potential for both silicon and graphite anodes. During cycling, the current collector is used for the in and out-flow of the electrons from an anode. The electrolyte molecules will be decomposed by these electrons at the anode surface because of the presence of strong voltages during anode operation.

Multiple various mechanisms are used by the evolution and characteristics of the SEI to influence the total battery performance fundamentally. The battery’s total charge capacity is reduced by SEI’s production through the consumption of some lithium that would be utilized for storing the charge, as various lithium compounds are contained by the SEI layer. This mechanism is a degradation mechanism which is called Loss of Lithium Inventory (LLI). In addition, lithium’s amount stored by the anode can be affected by the lithium permeability of the SEI’s, whereas the electron resistivity of the SEI can determine the growth rate of the SEI. SEI formation is one of the most usually utilized electrolyte compositions when lithium hexafluorophosphate (LiPF6) salts dissolved in carbonate solvent is being used.

Chemical reactions between the trace amounts of water and electrolytes can cause the formation of SEI, forming hydrofluoric acid (HF), which then decreases the performance. A very major part is played by the SEI in capacity degradation in a lithium-silicon battery because of the large volumetric changes during the cycling. The SEI layer on top of it is cracked by the anode material’s expansion and contraction, exposing direct contact of more of the anode material with the electrolyte, and that leads to further LLl-based degradation and SEI production. It is important to understand the SEI layer’s composition and structure throughout cycling if we want to enhance the stability of SEI and thus enhance the battery performance. Although, the composition of the SEI for both silicon-based and graphitic anodes is not completely understood.

Phases of SEI’s formation

Three different phases of the formation of SEI were identified by Heiskanen et al. for graphitic anodes in ethylene carbonate (EC) electrolyte and LiPF6. EC and LiPF6 reduction first leads to an SEI that is usually lithium ethylene dicarbonate (LEDC) and lithium fluoride (LiF). LEDC then subsequently decomposes into a broad number of components, which can be insoluble, gaseous, solid, or soluble in the electrolyte. The SEI layer becomes more porous because of the production of electrolytically-soluble molecules and gases, as these species will diffuse away from the surface of the anode. Electrolytes are exposed to the surface of the anode by this SEI porosity, which leads to the production of more LiF and LEDC on the SEI layer’s exterior. These mechanisms overall lead to the production of an inner SEI layer, which usually possesses an exterior SEI made up of the LiF and LEDC, and the electrolytically insoluble compounds.

Electrolyte reduction forms LiF and LEDC. The same 2-layer SEI structure appears as a result of a silicon-anode battery, in which organic compounds form an outer layer whereas inorganic compounds produce an inner layer. As the electrolyte makes up the SEI, the electrolyte composition can be adjusted and can have huge effects on lithium-silicon batteries’ capacity retention. In conclusion, there have been tests of a broad number of electrolyte additives and they provided capacity enhancements, like additional carbonates (like vinylene carbonate and fluoroethylene carbonate), ethers, citric acid, succinic anhydride, and silane molecules. These additives have the potential to use various mechanisms for making performance improvements. Silane highlighted another potential mechanism and it can produce Si-O networks on the anode’s surface which stabilizes the deposited organic SEI layer on its top.

Silicon full-cell designs

Silicon anodes were usually tested in a Si-half-cell or as a cathode versus Li metal for early-stage research purposes. Fuel cell performance was evaluated by pairing the as-formed Si anodes with the commercial cathodes due to the constant advancement in Si anode research. The replacement for graphite anodes is Si. Li-rich cathodes, LiMn2O4, LiFePO4, LiCoO2, etc are the corresponding cathode of choice.

A more practical evaluation of the cells is displayed by the production of a fuel-cell Si battery and it brought the research and its application in practical life one step closer. Now total energy densities can be more specifically evaluated with a full cell. In 2009, Cui et al. in their early work displayed a 1 mg cm-2 loading of Si NW anode paired with LiCoO2 of 10 mg cm-2 for delivering capacity retention of 80%, same as the cell with Li metal as anode. Moreover, when Si NW anode was used, 4 mAh cm-2 of commercially comparable areal capacity was obtained with the full cell.

Fabrication of fuel-cell

A fuel cell was fabricated by Son et al. in a 18650 type battery with 3.8 mAh cm-2 of a little low specific areal capacity but considered 972 Wh L-1 of volumetric energy density even after accounting for the thickness of the current collector, electrodes, and separator to be approximately 105 micrometers. An increase of 80% in volumetric energy density is possessed by this Si LIB as compared to the commercial batteries, and after 200 cycles, it has 72% cycle retention too. Typically, the electrode that is utilized for a Si-anode half-cell is also utilized in Li metal oxide fuel cells and Si anode. Pope et al. recently gave an interesting analysis on the volumetric and gravimetric energy density of the lithium-sulfur battery for sulfur’s given areal loading.

Conclusion

Due to silicon’s remarkably high specific capacity, there have been extensive studies on silicon as a material of anode for lithium-ion batteries (LIB). LIBs have different applications among various industries because of their stable performance, comparatively high energy density, and environmental benignity. There is a great demand for batteries with enhanced safety, lower cost, higher power, and energy density in this regard. There

​How to use mesocarbon microbeads graphite micron powders in the battery industry, its properties, and potential use

Mesocarbon microbeads are the particles of graphite that are either present or instilled in the lithium-ion batteries so that the anodes of these batteries can be made functional. Their specific surface area is approximately equal to 2022 m2/g whereas their bulk density is almost equal to 1.324 g/cm3. They are excessively being used in the lithium-ion batteries and the battery industry as a whole.

Their properties are quite vast too that is why the usage of these MCMBs is exceeding for quite some time now. A brief explanation of how these mesocarbon microbeads are being used is given in this article as it undoubtedly holds a great deal of importance in the battery industry.

 

Introduction

Mesocarbon microbeads (MCMBs) are the remarkable precursor of the lithium-ion battery anode materials because of their unique microstructure, homogeneous shrinkage, excellent sphericity, and uniform size. Typically, mesocarbon microbeads are made from coal tar pitch (CTP) with few additives. There is a variation in the MCMBs microstructure of different additives. The electrochemical performance of MCMB is greatly influenced by the MCMBs’ microstructure.

The MCMBs microstructure is measured to be the global type or Brooks-Taylor type with the poly-aromatic molecules almost parallel to each other and perpendicular to the sphere’s surface, which is appropriate for the desertion and insertion of lithium-ion. There are many studies on the influence of various additives, for instance, boron, carbon nanotubes, flake graphite, ferrocene, and carbon black.

Effects on the preparation

Different additives have different effects on the synthesis of MCMBs. The effects can be chemical or they can be physical too. Based on the physical effects, MCMBs formation, like its size and shape was physically affected as the additives didn’t react with polyaromatic hydrocarbons. Based on chemical effects, it was seen that the production of MCMBs is accelerated when the additives catalytically react with polyaromatic hydrocarbons. Although, because of chemical additive’s different characteristics, the chemical additives have different effect mechanisms on MCMBs formation. Indirect coal liquefaction process, one of the products is Direct coal liquefaction residue (DCLR), with characteristics of high aromatics, high sulfur, and high ash. A method should be necessarily provided for DCLR’s high-value application if we want to enhance the economic advantages of direct coal liquefaction. Alike CTP, DCLR is also converted from coal. Thus, DCLR can be utilized for making high value-added carbon materials for instance MCMBs, carbon fibers, and carbon foam. Although, it was found by Chang in 2017 that making a large amount of MCMBs with uniform size by only DCR is difficult as the mesophase spheres can easily melt during the synthesis. Here, there are discussions on the preparation of MCMBs in DCLR’s presence by CTP, and the DCLR’s effects on MCMBs’ characteristics and formation are also discussed.

Characterization

Sample analysis was done which is an elemental analysis and it was done by using the cube elemental analyzer known as the Vario Micro one. All the hydrogen-related spectra of nuclear magnetic resonance were being recorded on the Avance-300 NMR spectrometer by the usage of CDCl3 as a solvent. Another spectrum was saved on a spectrometry device known as the Nicolet Nexus 470 FTIR spectrometer. The full form of FTIR is Fourier transform infrared spectroscope. Other than that, the frequency is also recorded for every spectrum which is seen scattering and it was estimated to be 15 times. To carry out the same characteristics, KBr discs were built in the same way as they always are with all the dry mixtures which were having 1 mg of the sample and 100 mg of the KBr.

Morphologies of MCMBs and graphitized MCMBs

It has been reported by various researchers that the sizes are not always uniform but upon the addition of DCLR-P, the MCMBs are enabled enough to have uniformity in their sizes. Due to the addition of DCLR-P at first, the size of MCMBs increases, and later on it decreases and becomes consistent with what the actual need is. This process is usually carried out to provide consistency to the particles and to create uniformity in their nature so that they can carry out their tasks as per the requirements without any hindrances or so. DCLR-P is a product that is used in the form of a nucleating agent to provide promotion for the assembling of MCMBs. While on the other hand it also plays a role in reducing the viscosity of the entire system as it possesses an aliphatic structure. Both these factors play a huge role in developing the MCMBs.

 

Properties of Mesocarbon Microbeads

There are certain properties of mesocarbon microbeads which make them unique in their functions that they perform. It includes homogenous size and that remarkable sphericity. Anyhow the product which is known as MCMBs10 was a rough product having a few tiny particles which usually play a role in making the units of MCMBs. Other than that they exhibit remarkable electrical performances which are possible because of the microtextural layers of carbon that are present in the graphitized MVMBs as they are parallel so it becomes easy for them to go along with each other. MCMBs are also rich in the characteristics of aromatic condensation which are helpful for various purposes too.

The performance of graphitized MCMBs10 as a negative electrode material for Li-ion batteries

Certain standards are gone through so that a better and proper analysis and report can be drawn out of it to conclude the efficacy of any product or so according to the national standard of China MCMBs were as well tested to check the way they perform as negative electrode material in the Lithium-ion batteries. After the results came out, it was concluded that the graphitized MCMBs have practically met all the requirements that are needed for the CMB-I after taking their sizes, density, specific surface area, and the initial efficiency of charge and discharge were taken into consideration. It is known by all that the graphitization degree can be calculated by the XRD analysis and along with it the Raman Spectra. Both of these are the authenticated ways in which this whole process can be carried out and on the other hand, the results too are completely reliable ones that is why these are considered as the standard methods.

In the light of XRD analysis

As mentioned above that the XRD analysis is the most reliable standard method then in the light of XRD analysis, it was reported that the extent of graphitized MCMB was about 56.44% which was slightly lower than the reference ranges. However, XRD analysis is a prolonged process and is not an easy one to carry out. A lot of hard work, struggle, determination, and efforts go into it so that a fruitful result can be achieved out of it. The bands which are centered at various distances and places go as per the requirement so that not even a single mistake is committed to achieving the desired outcomes. Other than the XRD analysis, Raman spectra are also carried out to reconfirm the results. Upon the tests, the low graphitization degree identifies that these are good in accordance because these are the desired results. So both these processes go hand in hand to make the process smoother and reliable in all the possible regards.

Lithium-ion battery research

In today’s world, lithium-ion batteries are being used so excessively because they are fulfilling all the needs and requirements of a good battery as they are excellent in performing their tasks and functions. This lithium-ion battery research is working on how it can play a role in the development of electrode materials having high-performance characteristics all through enhancing the features keeping in mind the conventional features as well. For this purpose, a lot of research and efforts have been carried out so that an exact and appropriate analysis can be done in the regard and all these efforts have been put in so that the optimization of cathodes and anodes having high voltage and high capacity respectively can be processed so that the entire battery’s energy content can be increased to a level where it can work to its maximum capacity without causing any distortions or so.

Reaction with transition metal oxides

Certain metal oxides are known to be the transition metal oxides written as MxOy. When these metal oxides react with lithium to form LiO2 and along with it metallic M has the oxidation state of 0. This is carried out through the process of conversion. This whole process involves a lot of changes the major one includes the electron exchange process which enables the Li-conversion electrode to keep the excellent capacity intact regarding conventional graphite anodes. The best thing about these metal oxides is that they are cheap, very much safe and their compatibility with the environment is excellent. Therefore, it is easy to change them with the common graphite anodes as these metal oxides have better energy content.

Structural changes

There are a lot of changes that happen in the batteries and among those structural changes are extremely highlighted ones. These changes then lead towards electrode pulverization and other than that electric contact is lost, both of which are happening because of the prolonged cycling. The high irreversible capacity is shown by the electrodes which are working along with the conversion process range from 30 to 60% and this usually happening during the first cycle. Other than that there might be an incomplete de-conversion reaction process going on which enables the metal to have a lower valence regarding the initial compound which is responsible for enhancing the inefficiency of cycling. A remarkable feature known as the Columbic efficiency enhances after the initially started cycles and their stabilization process.

Issue of conversion anodes

According to the recent researches, an evident structural variation problem of the conversion of anodes has been found out and the possibility of ruling it out is by taking up the composite morphologies of the nanostructured particles which shall be relying on metal oxide materials which are active and possess buffer matrices, examples of which are carbon and all the metals that possess volume changes and give insurance about the electron transport process happening within the electrode. It has been suggested that the high-energy mechanical milling of the oxides shall be carried out by the carbon additives as it is of low cost and has versatility which are the key elements for the preparation of composite anodes. Though a lot of researches have been carried out in this regard there are still some areas that are lacking and need to be worked out. Therefore, more consideration in this regard has been happening so to make it better and effective in all the possible ways.

Full cells having conversion electrodes

Along with all the other things, certain problems are somehow related to the full cells that possess conversion electrodes which are characterized by the high capacity and a voltage window that is wide working in its range. However, these lithium cells have always shown remarkable behaviors but there were a few miss points including limited cycling stability and voltage profile retention. Therefore, to rule out these two a modified conversion anode was structured which included CuO and Fe2O3 in their compositions which enhanced the total working mechanics of these cells and batteries. The electrochemical properties were also expressed by these batteries in the form of stability of cycling, Coulombic efficiency, and the delivering capacity.

Application

Li1.35Ni0.48Fe0.1Mn1.72O4 was chosen in combination with the CuO-Fe2O3-carbon composite for application in the full-cell. It was suggested that the most powerful approach for improving cycling performance is the metal substitution of high-voltage spinels. According to more research, Mn and Ni’s partial replacement by tri- and bi-valent ions, like Cr, Co, Al, Ru, Fe, affects the characteristics of an electrode in terms of the cation ordering degree, conduction mechanism, rate of charge transfer, metal-ion dissolution, and Mn3+ concentration. Also, modifications in surface and morphology may be induced by cation doping by affecting its long-term cyclability and the electrode reactivity towards the electrolyte. There are a lot of applications that are carried out by these mesocarbon microbeads graphite micron powders, a few of which are listed and explained below as they are excellent in all the functions that they perform.

MCMB from petroleum residua

Treated in heat under different conditions and derived from residua of petroleum, Mesocarbon microbeads (MCMB) were characterized by electron paramagnetic resonance (EPR), Fourier transforms infrared spectroscopy (FTIR), proton magnetic resonance (PMR), electron diffraction, and X-ray.

After heating, the presence of hydrogen’s two separate forms is retained to7508C under vacuum. Graphitization to 30008C results in graphite ribbon-like particles surrounding microbeads of a size of few microns. As the EPR observed, the crystalline graphite mono domains are semi-metallic or with a small bandgap. Even after heat treatment at 30008C, the localized paramagnetic defects are not eliminated in the microbeads. Such characteristics condition these material’s aptitude toward their usage in sodium and lithium electrochemical cells.

A reversible intercalation behavior is shown by the samples which are made at 7508C, while those samples that are made at 30008C evidence solvent decomposition lead to a non-reversible extended discharge plateau when utilizing the sodium perchlorate electrolyte that is dissolved in pure propylene carbonate.

MCMB in Lithium-ion batteries

Lithium is a very important element of the periodic table and it has a very effective manner in the field of science and all the fields related to it. It is one of the most renowned and beneficial products of lithium and so are lithium-ion batteries. They are most certainly used for electronics of all sorts but most commonly for portable electronics. They come with great characteristics and properties and it is because of them that they are highly profitable in the market. For Lithium-Ion batteries, Mesocarbon Microbeads (MCMB) Graphite Micron Powder is one of the most efficient ways to utilize the li-ion batteries as it brings authenticity to the batteries and their working and functioning.

The relation with soft carbons

Right now, the concern is the usage of carbon-based intercalation compounds for lithium-ion cells’ negative electrode, expanding to various forms and allotropes of artificial and natural carbon. From their structural point of view, graphite-related carbons are capable of being classified into graphitized solid, turbostratic material, and unorganized carbon. There is a notable difference in the capacity for lithium intercalation into each of these forms. Depending on the facility of transforming into graphite, there is a classification of less organized forms into ‘hard’ and ‘soft’ carbons, and above 20008C into the graphitic carbon, while even when heat-treated at 28008C, the graphitization’s characteristics signs are not shown by the latter.

Most of the cokes are considered as the soft carbons, mesocarbon microbeads (MCMB) are in that list of most cokes. Other than being the first commercial lithium-ion cell’s part, the most broadly utilized form of soft graphitizable carbons is petroleum coke. In comparison with the usage of other graphitizable forms, the intercalation electrode’s performance utilizing coke as an active material is mostly limited.

The promising behavior of MCMB

Promising behavior has been specifically displayed by the MCMB. The material has a low specific surface area and contains roughly spherical structures (microbeads) of a diameter of 1–40 mm. During the Lithium-ion cells charging and discharging processes, it has a high packing density which ignores the prolonged side reactions with the electrolyte. Due to all this, the observed capacity reaches 750 mAh/g value which is double the graphite’s theoretical values (for LiC, 372 mAh/g). There have been reports on the evolution of the 6 electrochemical performance of MCMBs with thermal treatment’s temperature, and behavior, similar to other soft carbons: decrease in capacity from 7008C, the highest value, to ca. 20008C, a minimum value, followed by an advanced increase.Recently, lithium-ion batteries gained a lot of interest because of their remarkable characteristics, for instance, environment-friendly, long cycle lives, and high energy densities. For electronic products like computers, laptops, and cellphones, lithium-ion batteries are significant power sources.

Carbon materials of Lithium-ion batteries

Generally, carbon materials are used in lithium-ion batteries as anode materials due to their high energy density, the stability of the structure during cycling, and small surface change. Mesocarbon microbeads are one of the carbon materials that is utilized as an anode in lithium-ion batteries. One special type of carbonaceous material for lithium-ion batteries is Mesocarbon Microbeads (MCMB) Graphite Micron Powder. With 1-50 µm diameter, a spherical shape is generally carried by the mesocarbon microbeads and when the mesocarbon microbeads are utilized in lithium-ion batteries as anode materials, a 300-340mAh/g reversible capacity and remarkable stability are provided by it, making it a big benefit for applications in which high capacity is needed.

Advantages or uses of mesocarbon microbeads

Another advantage of mesocarbon microbeads is that they can be in combination with silicon to have higher capacities and recharge-ability. It is a fact that among all the kinds of carbon anode materials, the best cyclability is possessed by the mesocarbon microbeads anode materials. When we combine mesocarbon microbeads with silicon to obtain an anode material, we can obtain Silicon – mesocarbon microbeads composite material with high capacity and satisfactory recharge-ability. So it is possible to extend the number of charging cycles of lithium-ion batteries by using silicon – mesocarbon microbeads composite anode material.

Conclusion

Mesocarbon microbeads are very useful and one of the most integral parts of a lithium-ion battery. They have been continuously in use because of the properties that they hold which are excellent in their terms and means. They have been highly applauded by all the researchers as well who have invested in these works. The potential use of MCMBs as expressed in this article can easily be seen and studied in lithium-ion batteries.