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Ferro Boron 25 µm 99.9%
Ferro Chrome HC 100 µm 99.5%
Ferro Chrome HC 44 µm 99.5%
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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 |
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 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, CO bonds, and O−CO 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.
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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.
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.
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.
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 rGO. rGO 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 battery, 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.
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.
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.