What is boron nitride? Boron nitride is a crystal composed of nitrogen atoms and boron atoms. The crystal structure is divided into hexagonal boron nitride (HBN), closely arranged hexagonal boron nitride (WBN), and cubic boron nitride. The crystal structure of hexagonal boron nitride has a similar graphite layered structure, presenting a loose, lubricating, moisture absorbing, lightweight, and other characteristics of white powder, so it is also known as "white graphite.". Theoretical density: 2.27g/cm3, specific gravity: 2.43, Mohr's hardness: 2. Hexagonal boron nitride has good electrical insulation, thermal conductivity, chemical stability, and no obvious melting point. It is 3000 ℃ in 0.1MPA nitrogen, heat resistant to 2000 ℃ in a neutral reducing atmosphere, and can be used at 2800 ℃ in nitrogen and argon. It has poor stability in oxygen atmosphere, and can be used at temperatures below 1000 ℃. The expansion coefficient of hexagonal boron nitride is equivalent to that of quartz, but its thermal conductivity is ten times that of quartz.
Properties of boron nitride Hexagonal boron nitride is insoluble in cold water. It does not react with weak acids and strong bases at room temperature, and is slightly soluble in hot acids. It can be decomposed only after being treated with molten sodium hydroxide and potassium hydroxide.
Various performance parameters of boron nitride:
1. High heat resistance: sublimated at 3000 ℃, its strength at 1800 ℃ is twice that of room temperature, it does not crack dozens of times after air cooling at 1500 ℃ to room temperature, and it does not soften at 2800 ℃ in inert gas.
2. High thermal conductivity: Hot pressed products have a thermal conductivity of 33W/M.K. Similar to pure iron, they have the highest thermal conductivity among ceramic materials at temperatures above 530 ℃.
3. Low thermal expansion coefficient: 2 × The expansion coefficient of 10-6 is second only to quartz glass and is the smallest among ceramics. In addition, it has high thermal conductivity, so it has excellent thermal shock resistance.
4. Excellent electrical performance: Good high-temperature insulation, 1014 Ω - cm at 25 ℃, and 103 Ω - cm at 2000 ℃. It is the best high-temperature insulation material in ceramics, with a breakdown voltage of 3KV/MV and a low dielectric loss of 2.5 at 108HZ × 10-4, with a dielectric constant of 4, permeable to microwave and infrared rays.
5. Good corrosion resistance: non reactive with general metals (iron, copper, aluminum, lead, etc.), rare earth metals, precious metals, semiconductor materials (germanium, silicon, potassium arsenide), glass, molten salts (crystal stone, fluoride, slag), inorganic acids, and alkalis.
6. Low friction coefficient: U is 0.16, does not increase at high temperatures, and is higher than molybdenum disulfide. Graphite is resistant to high temperatures. The oxidation atmosphere can be used to 900 ℃, and it can be used to 2000 ℃ under vacuum.
7. High purity, good B high: its impurity content is less than 10 PPM, while the content of B is greater than 43.6%.
8. Machinability: Its hardness is Mohs 2, so it can be processed into components with high accuracy using general machining methods.
Uses of hexagonal boron nitride
Hexagonal boron nitride can be used to manufacture TiB2/BN composite ceramics, as well as advanced refractory and superhard materials, separation rings for horizontal continuous rolling steel, high-temperature resistant lubricants and coatings, and is also a raw material for synthesizing cubic boron nitride.
Specific use:
1. Boron nitride is a release agent for metal molding and a lubricant for metal wire drawing.
2. Boron nitride is a special electrolytic and resistive material at high temperatures.
3. Boron nitride is suitable for high-temperature solid lubricants, extrusion anti wear additives, additives for producing ceramic composites, refractory materials, and antioxidant additives, especially for molten metal Faust applications, thermal reinforcement additives, and high-temperature resistant insulation materials.
4. Boron nitride is suitable for heat sealing desiccants for transistors and additives for polymers such as plastic resins.
5. Boron nitride products pressed into various shapes can be used as high-temperature, high-voltage, insulation, and heat dissipation components.
6. Boron nitride is a thermal shielding material in aerospace.
7. With the participation of catalysts, cubic boron nitride can be converted into hard, diamond-like cubic boron nitride after high-temperature and high-pressure treatment.
8. Boron nitride is the structural material of atomic reactors.
9. Boron nitride is suitable for nozzles of aircraft and rocket engines.
10. Boron nitride is an insulator for high-voltage, high-frequency electricity and plasma arc welding.
11. Boron nitride is a packaging material that prevents neutron radiation.
12. The superhard material processed from boron nitride can be made into high-speed cutting tools and drill bits for geological exploration and oil drilling.
13. Boron nitride is used in metallurgy as a separation ring for continuous casting of steel, a flow slot for amorphous iron, and a mold release agent for continuous casting of aluminum (various optical glass release agents)
14. Boron nitride is an evaporation boat for aluminum plating on various capacitor films, picture tubes, and displays.
15. Boron nitride is suitable for various fresh-keeping aluminum plated packaging bags, etc.
16. Boron nitride is a variety of laser anti-counterfeit aluminum plating, trademark stamping materials, various cigarette labels, beer labels, packaging boxes, cigarette packaging boxes, aluminum plating, and so on.
17. Boron nitride is suitable for cosmetics as a filler for lipstick. It is non-toxic, lubricious, and glossy.
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