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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

 

Silicon Boride SiB6 Powder CAS 12008-29-6

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

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

What is Boron Carbide Powder B4C?

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

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

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

 

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

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

Boron Doped Graphene and its application as electrode material for supercapacitors

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

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

Introduction

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

 

Graphene doping

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

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

Nitrogen and boron-doped graphene

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

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

Preparation

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

Thermal shock treatment

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

Trace levels of elements

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

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

Characterization of density

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

Sizes of crystallites

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

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

Obtained ratios

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

Combustible elemental analysis

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

Electrical resistivity

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

Cyclic voltammograms

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

Weight specific capacitance

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

In comparison to non-doped parts

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

Surface plasmon resonance

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

Single crystalline gold surface

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

Novel materials

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

 

Enhancements in graphene’s characteristics

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

Catalyst deposition

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

Cell fabrication

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

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

Electrochemical testing

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

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

Characterization methods

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

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

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

Raman spectroscopy

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

Conclusion

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

Lithium Hydroxide Monohydrate Application Areas

Lithium Hydroxide Monohydrate Application Areas

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

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

Introduction

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

Useful test case

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

Spectra’s interpretation

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

Comparison with crystal structure

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

 

Characteristics and usages

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

Availability in different volumes

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

INS spectroscopy

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

The initial calculations

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

Intermolecular angles and distances

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

Findings

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

Lithium-ion batteries

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

 

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

you can read our other blog post.

Grease

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

Carbon dioxide scrubbing

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

2 LiOH•H2O + CO2 → Li2CO3 + 3 H2O

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

Precursor

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

Other usages

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

Structural Changes during lithium hydroxide monohydrate’s Carbonation

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

Temperature variations

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

Thermal energy storage technologies

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

Thermochemical heat storage

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

Example

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

Carbon nanospheres and nanotubes

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

 

Application

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

The Microstructure Characterization of Lithium Hydroxide Monohydrate-Based TCMs

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

Structure formations

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

Observations

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

Nitrogen adsorption-desorption isotherms

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

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

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

Samplings

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

Heat storage density

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

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

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

Contribution of nanoparticles

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

Conclusion

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

Synthesis and Application Areas of Cerium Oxide (CeO2)

Synthesis and Application Areas of Cerium Oxide (CeO2)

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

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

Introduction

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

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

 

A rare-earth metal

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

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

Sizes and ratios

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

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

Advances in nanoparticles

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

Non-stoichiometry levels

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

Electronic structure

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

Importance of oxygen vacancies in CeO2

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

Nano‐size effects

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

Production of Cerium Oxide Nanoparticles

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

Formation of protein corona

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

Traditional Synthesis Methods

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

Green Synthesis Methods

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

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

Strategies of green synthesis method

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

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

 

Bio-Relevant Activities of Cerium Oxide Nanoparticles

Enzyme Mimetic Activities

  • Degradation through catalase:

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

  • Phosphatase Mimetic Activity

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

Evidence for Bio-Relevant Activities of Cerium Oxide Nanoparticles

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

In Vitro Studies

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

Redox-active cerium oxide nanoparticles

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

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

Strategies in cancer therapy

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

Nanoparticles in Medicine

Leukemia cells

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

Cytotoxicity

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

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

In Vivo Studies

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

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

Tumor growth in ovarian cancer

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

Retinitis pigmentosa

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

Obesity treatment

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

Treatment of hepatic ischemia

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

 

Conclusion

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

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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

 

Silicon Boride SiB6 Powder CAS 12008-29-6

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

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

What is Boron Carbide Powder B4C?

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

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

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

 

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

Properties and applications of Aluminum Oxide nanoparticles

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

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

Introduction

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

 

Aluminum oxide

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

Aluminum oxide nanoparticles

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

Properties of nanoscale colloidal alumina particles

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

Properties of the nanoscale fibers of aluminum oxide

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

Physiochemical properties

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

Structure determination

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

Thermal properties

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

Manufacturing process

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

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

Derivation of aluminum oxide

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

Recycling of virgin aluminum

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

Bayer process

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

Formation of fumes

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

 

Applications of Aluminum Oxide Nanoparticles

Drug delivery

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

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

Effect on solubility

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

Biosensing

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

Florescent nature of aluminum oxide

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

Cancer therapy

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

Surface potential and viability

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

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

Anti-microbial effects

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

Aluminum oxide as a silver nanocomposite

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

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

Treatment of other diseases

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

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

Bimolecular preservation and stabilization

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

Immunotherapy

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

Pharmaceuticals

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

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

 

 

Advantages

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

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

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

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

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

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

Conclusion

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

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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

 

Silicon Boride SiB6 Powder CAS 12008-29-6

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

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

What is Boron Carbide Powder B4C?

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

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

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

 

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

Properties and applications of Aluminum Oxide nanoparticles

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

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

Introduction

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

 

Aluminum oxide

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

Aluminum oxide nanoparticles

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

Properties of nanoscale colloidal alumina particles

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

Properties of the nanoscale fibers of aluminum oxide

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

Physiochemical properties

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

Structure determination

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

Thermal properties

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

Manufacturing process

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

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

Derivation of aluminum oxide

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

Recycling of virgin aluminum

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

Bayer process

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

Formation of fumes

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

 

Applications of Aluminum Oxide Nanoparticles

Drug delivery

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

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

Effect on solubility

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

Biosensing

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

Florescent nature of aluminum oxide

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

Cancer therapy

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

Surface potential and viability

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

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

Anti-microbial effects

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

Aluminum oxide as a silver nanocomposite

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

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

Treatment of other diseases

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

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

Bimolecular preservation and stabilization

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

Immunotherapy

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

Pharmaceuticals

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

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

 

 

Advantages

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

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

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

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

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

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

Conclusion

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

XTEMOS ELEMENT

BLOG CHESS

What is Silicon Boride Powder?

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

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

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

 

Silicon Boride SiB6 Powder CAS 12008-29-6

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

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

What is Boron Carbide Powder B4C?

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

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

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

 

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

Properties and applications of Aluminum Oxide nanoparticles

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

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

Introduction

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

 

Aluminum oxide

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

Aluminum oxide nanoparticles

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

Properties of nanoscale colloidal alumina particles

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

Properties of the nanoscale fibers of aluminum oxide

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

Physiochemical properties

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

Structure determination

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

Thermal properties

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

Manufacturing process

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

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

Derivation of aluminum oxide

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

Recycling of virgin aluminum

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

Bayer process

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

Formation of fumes

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

 

Applications of Aluminum Oxide Nanoparticles

Drug delivery

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

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

Effect on solubility

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

Biosensing

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

Florescent nature of aluminum oxide

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

Cancer therapy

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

Surface potential and viability

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

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

Anti-microbial effects

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

Aluminum oxide as a silver nanocomposite

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

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

Treatment of other diseases

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

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

Bimolecular preservation and stabilization

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

Immunotherapy

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

Pharmaceuticals

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

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

 

 

Advantages

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

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

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

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

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

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

Conclusion

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

Boron Doped Graphene and its application as electrode material for supercapacitors

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

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

Introduction

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

 

Graphene doping

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

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

Nitrogen and boron-doped graphene

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

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

Preparation

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

Thermal shock treatment

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

Trace levels of elements

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

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

Characterization of density

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

Sizes of crystallites

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

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

Obtained ratios

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

Combustible elemental analysis

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

Electrical resistivity

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

Cyclic voltammograms

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

Weight specific capacitance

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

In comparison to non-doped parts

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

Surface plasmon resonance

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

Single crystalline gold surface

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

Novel materials

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

 

Enhancements in graphene’s characteristics

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

Catalyst deposition

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

Cell fabrication

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

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

Electrochemical testing

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

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

Characterization methods

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

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

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

Raman spectroscopy

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

Conclusion

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

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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

 

Silicon Boride SiB6 Powder CAS 12008-29-6

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

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

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What is Boron Carbide Powder B4C?

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

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

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

 

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

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