English name of boron nitride: boron nitride
Molecular formula: BN molecular weight: 24.8 1 (according to international atomic weight 1979)
Quality standard: enterprise standard (QJ/YH02? 08-89)
Boron nitride is a crystal composed of nitrogen atoms and boron atoms. Crystal structure can be divided into hexagonal boron nitride (HBN), close packed hexagonal boron nitride (WBN) and cubic boron nitride. The crystal structure of hexagonal boron nitride is similar to graphite layered structure, showing white powder, which has the characteristics of looseness, lubrication, moisture absorption and light weight, so it is also called "white graphite". Theoretical density is 2.27g/cm3, specific gravity is 2.43, and Mohs hardness.
Hexagonal boron nitride has good electrical insulation, thermal conductivity and chemical stability; It has no obvious melting point, sublimes at 3000℃ in 0. 1MPA nitrogen, melts at 3000℃ in inert gas, resists heat up to 2000℃ in neutral reducing atmosphere, reaches 2800℃ in nitrogen and argon, has poor stability in oxygen atmosphere, and its service temperature is lower than 1000℃. The expansion coefficient of hexagonal boron nitride is equivalent to that of aging, but its thermal conductivity is ten times that of aging.
Hexagonal boron nitride is insoluble in cold water, and hydrolysis is very slow when water boils, resulting in a small amount of boric acid and nitrogen. It does not react with weak acids and strong bases at room temperature, but is slightly soluble in hot acids. It can only be decomposed by treatment with molten sodium hydroxide and potassium hydroxide.
Technical indicators of boron nitride: 1, specification 99, BN ≥ 99% B2O3 ≤ 0.5% Particle size D50(um)≤2.0 2, specification 98, B N≥98%.
B2O3≤0.5% Particle size D50(μm)≤2.0
Various performance parameters of boron nitride: (1) High heat resistance: sublimation at 3000℃, twice the strength at room temperature at 1800℃, and cooling to room temperature at 1500℃.
In inert gas, it does not break for 10 times and does not soften at 2800℃. (2) High thermal conductivity: the hot-pressed product is 33W/M.K, which, like pure iron, has the largest thermal conductivity among ceramic materials above 530℃. (3) Low thermal expansion coefficient: The thermal expansion coefficient of 2× 10-6 is the smallest among ceramics, second only to the timely glass. In addition, it has high thermal conductivity, so it has good thermal shock resistance. (4) Excellent electrical performance: good high-temperature insulation, 10 14ω-cm at 25℃ and 103ω-cm at 2000℃. It is the best high-temperature insulating material in ceramics, and the dielectric loss is as low as 2.5 at breakdown voltage of 3KV/MM and 108HZ. (5) Good corrosion resistance: Compared with common metals (iron, copper, aluminum, lead, etc.). ) and rare earth metals.
Most of them are precious. Semiconductor materials (germanium, silicon, potassium arsenic), glass, molten salt (crystal stone, fluoride, slag), inorganic acid and alkali do not react. (6) Low friction coefficient: U is 0. 16, which does not increase at high temperature, and is more resistant to high temperature than molybdenum disulfide and graphite. The oxidation atmosphere can reach 900℃ and the vacuum can reach 2000℃. (7) High purity and high B content: the impurity content is less than 10PPM, while the B content is more than 43.6%. (8) Machinability: its hardness is Mohs 2, so it can be processed into parts with high precision by general processing methods.
Uses of hexagonal boron nitride:
Hexagonal boron nitride can be used to manufacture TiB2/BN composite ceramics, as well as advanced refractories and superhard materials, horizontal continuous rolling separation rings, high-temperature lubricants and high-temperature coatings, and it is also the raw material for synthesizing cubic boron nitride.
Specific use:
(1) Release agent for metal molding and lubricant for metal wire drawing.
(2) Special electrolytic and resistive materials at high temperature.
(3) High-temperature solid lubricants, extrusion antiwear additives, additives for producing ceramic composite materials, refractory materials and antioxidant additives, especially in the case of corrosion resistance of molten metal, thermal enhancement additives and high-temperature resistant insulating materials.
(4) Heat sealing desiccants for transistors and additives for polymers such as plastic resin.
(5) boron nitride products pressed into various shapes can be used as high temperature, high pressure, insulation and heat dissipation elements.
(6) Thermal insulation materials in aerospace.
(7) With the participation of catalyst, it can be transformed into cubic boron nitride as hard as diamond after high temperature and high pressure treatment.
(8) Structural materials of atomic reactors.
(9) Nozzles for aircraft and rocket engines.
(10) Insulator of high voltage and high frequency arc and plasma arc.
(1 1) Packaging materials to prevent neutron radiation.
(12) superhard materials made of boron nitride can be made into high-speed cutting tools and drill bits for geological exploration and oil drilling.
(13) metallurgical separation ring for continuous casting steel, runner for amorphous iron, and release agent for continuous casting aluminum (various optical glass release agents).
(14) Making evaporation boats for aluminum plating of capacitor films, picture tubes and displays.
(15) All kinds of fresh-keeping aluminized packaging bags, etc.
(16) All kinds of laser anti-counterfeiting aluminizing, trademark bronzing materials, all kinds of cigarette labels, beer labels, packaging boxes and cigarette packaging boxes are aluminized.
(17) Cosmetic, used as a filler of lipstick, is nontoxic, smooth and shiny, and is the best lipstick in France.