New breakthrough: “white graphene” absorbs greasy dirt effectively and can be used repeatedly
Researchers from the Advanced Materials Research Institute of Deakin University found that boron nitride, also known as “white graphene”, is capable of cleaning polluted water and is a new type of material that promises bright market prospect. The atoms of “white graphene” form interconnected fence-shaped structure which can effectively absorb organic pollutants, such as chemical products and engine oil.
The "white graphene" atoms form interconnected, fence-shaped structures that can effectively absorb organic contaminants such as chemical products and engine oils. The advantage over similar nanomaterials is that this new material is very easy to clean and reuse. Studies have shown that the performance of boron nitride is significantly better than many nanomaterials, and is much larger than traditional materials.
About Boron Nitride
Boron nitride is a crystal composed of a nitrogen atom and a boron atom. The chemical composition is 43.6% boron and 56.4% nitrogen with four different variants: hexagonal boron nitride (H-BN), rhombohtic boron nitride (R-BN), cubic boron nitride (C-BN) And hexagonal boron nitride (W-BN/wurtzite boron nitride).
BN can be prepared by eutecticizing B2O3 with NH4Cl, or by burning elemental boron in NH3. The commonly obtained boron nitride is a graphite layered structure, ie, hexagonal boron nitride, which is white powder that is loose, lubricated, easily absorbing moisture, light in weight, insoluble, and resistant to high temperatures, and is also called “white graphite”. .
The other is diamond type, cubic boron nitride. Similar to the principle of converting graphite into diamond, graphite boron nitride can be transformed into diamond-shaped boron nitride at high temperature (1800°C) and high pressure (800Mpa). The B-N bond length (156 pm) in this boron nitride is similar to that of diamond at the C-C bond length (154 pm), and its density is similar to that of diamond. Its hardness is comparable to diamond and its heat resistance is better than that of diamond. It is a new high-temperature superhard material used for making drills, grinding tools and cutting tools.
Hexagonal boron nitride has no significant melting point and is sublimed at 3000°C in 0.1 MPA nitrogen. It has a melting point of 3000°C in an inert atmosphere, a temperature of 2000°C in a neutral reducing atmosphere, and a temperature of 2800°C in nitrogen and argon. The stability in oxygen atmosphere is poor, and the use temperature is below 1000°C. Hexagonal boron nitride is insoluble in cold water. When water is boiled, it is hydrolyzed very slowly and produces a small amount of boric acid and nitrogen. It does not react with weak acid and strong alkali at room temperature. It is slightly soluble in hot acid. It is treated with molten sodium hydroxide and potassium hydroxide. To break down.
Hexagonal boron nitride is one of the most conductive materials in ceramic materials. The thermal conductivity is ten times that of quartz. The high thermal conductivity hot press product is 33W/MK and pure iron. The expansion coefficient is equivalent to quartz and is the smallest among ceramics. The thermal expansion coefficient in the c-axis direction is 41×10^6/C and in the d-axis direction is −2.3×10^6/C, so the thermal shock resistance performance is good. Boron nitride is also the best high-temperature insulating material in ceramics, breakdown voltage 3KV/MM, low dielectric loss 108HZ is 2.5x10^-4, dielectric constant is 4, can penetrate microwave and infrared.
Hexagonal boron nitride has a coefficient of friction as low as 0.16 and does not increase at high temperatures. Compared to molybdenum disulfide, graphite has a higher temperature resistance. The oxidizing atmosphere can be used up to 900°C and can be used under vacuum to 2000°C. Lubricating performance at room temperature is poor, so it is often used with fluorinated graphite, graphite and molybdenum disulfide mixed high-temperature lubricant, boron nitride powder dispersed in oil or water can be used as drawing or pressing forming lubricant, can also be used Lubricants for sliding parts of high-temperature furnaces and sintered bodies of boron nitride can be used as materials for bearings and sliding parts having self-lubricating properties.
Hexagonal boron nitride has a compressive strength of 170 MPa and its machinability has a hardness of 2 Mohs. Therefore, it can be processed into high-precision parts by general machining methods.
The use of hexagonal boron nitride
1. High-temperature solid lubricants, such as various optical glass mold release agents, metal mold release agents and metal wire drawing lubricants, metallurgical separation rings for continuous casting steel
2. Special electrolysis and resistance materials in high temperature conditions, such as high-voltage high-frequency electric and plasma arc insulators, and various aluminum plating evaporation boats
3. Packing materials to prevent neutron radiation, such as: structural materials of atomic reactors
4. Pressed into a variety of shapes, used as high temperature, high pressure, insulation, heat dissipation components, such as jets of aircraft, rocket engines
5. Superhard materials made by machining can be made into high-speed cutting tools and drill bits for geological exploration and oil drilling.
The advantages of using boron nitride
The boron nitride coating uses high-quality boron nitride, which is characterized by high temperature resistance, no adhesion, corrosion resistance, and heat dissipation and heat transfer. Non-wetting with aluminum water provides full protection on the surface of materials that are in direct contact with molten aluminum, magnesium, zinc alloys and their molten slag.
Boron nitride coating is widely used in gravity casting, low pressure casting, stamping, forging and powder metallurgy. Corrosion prevention, lubrication and mold release between non-ferrous molten metal, molds and carriers, avoiding chemical attack, making it easy to release film, prolonging the service life of molds and carriers, and increasing productivity, or use as molten metal and runners The protective agent between the isolation layer, effective maintenance of the flow cell and its apparatus, can protect the surface of the workpiece during welding and brazing in the furnace, avoid welding spatter splashing, and provide excellent welding protection.
Boron nitride has excellent lubricating properties and high temperature stability. Even at extremely high temperatures (high temperature resistant to 2800°C), boron nitride can maintain its lubricity and inertness. The use of boron nitride coating can prevent adhesion, thereby prolonging the life of the die/die, improving the surface finish of the product, and shortening the production time. The sintering of metal and ceramic powders is usually performed on a graphite plate, and a layer of graphite is coated thereon. The boron nitride coating can obviously remove the carbon contamination, reaction and bonding phenomenon that may occur in the sintering process. During the metal melting and metal forming operations, the boron nitride coating can be applied to the surface of the mold that is in contact with the hot or molten metal to avoid chemical attack, easier demolding, and longer mold/die life.
Boron nitride coating's high temperature lubrication is an ideal material in the glass processing process, which helps to minimize the surface defects of glass products, make it easier to mold release, improve the life of the mold/die, and reduce the mold Most of the glass will not stick to boron nitride for the time required for cleaning.
The unique formula of boron nitride coating can be applied to both hot and cold surfaces, and it is far superior to other brands in terms of corrosion resistance, lubricity, adhesion and wear resistance.
Boron nitride in hand graphite thin Superhard materials attract attention
Researchers at the Massachusetts Institute of Technology (MIT) introduced a kind of monoatomic hexagonal boron nitride, ie, thickness, properties, and graphene-like materials, and placed a layer of graphene on it. The resulting mixed material includes graphene. The conductive properties also have the energy gap necessary to build a transistor. Scientists define this discovery as a breakthrough in future technology.
Since the birth of graphene more than a decade ago, this material has always fascinated scientists. This single-atom-thick carbon material has excellent electronic properties, strength and ultra-light weight, and its use is also expanding. However, how to implant an energy gap to manufacture transistors and other electronic devices has always kept scientists from doing anything about it. . Today, researchers at the Massachusetts Institute of Technology (MIT) have made major breakthroughs in this area and are even expected to change some of the theoretical predictions of graphene physics. According to media reports, researchers have introduced another hexagonal boron nitride with single-atom thickness, properties, and graphene-like materials, and placed a layer of graphene on it. The resulting hybrid material has both conductive properties of graphene. It also has the energy gap necessary to build a transistor.