1. According to the main crystal phase, ceramics with a content of 99% by mass are classified as corundum ceramics. The sintering temperature is about 65438 0700℃. With the increase of Al2O3 content, sintering becomes more and more difficult, and sintering AIDS are generally needed. Main properties: density 3.9g/cm3, bending strength 370~450MPa, thermal expansion coefficient 6.7x10-6/℃ (20 ~100℃), dielectric strength 25 ~ 30mv/m, volume resistivity10/kloc. It is often used to make crucibles, porcelain boats, refractory furnace tubes, etc.
2. Alumina ceramics with 95% (mass) content, the main crystal phase is α-Al2O3, and the sintering temperature is about1650℃ 20℃. Main properties: the relative dielectric constant is 8.5 ~ 9.6, the dielectric strength 15 ~ 18mv/m, the volume resistivity1010/0/2 ω m, and the bending resistance. As a ceramic for devices, it is widely used. 1. Basic information
English name boron nitride
The molecular formula BN has a molecular weight of 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".
2. Physical and chemical properties
Theoretical density is 2.27g/cm3, specific gravity is 2.43, and Mohs hardness is 2. 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.
3. 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(um)≤2.0.
4. Various performance parameters of boron nitride
1, high heat resistance and sublimation at 3000℃, its strength 1800℃ is twice that of room temperature, 1500℃ does not break after air cooling to room temperature for dozens of times, and does not soften at 2800℃ in inert gas.
2. The hot-pressed product with high thermal conductivity is 33 w/m.k, which, like pure iron, has the largest thermal conductivity among ceramic materials above 530℃.
The low thermal expansion coefficient of 3.2× 10-6 is the smallest among ceramics, second only to timely glass. In addition, it has high thermal conductivity, so it has good thermal shock resistance.
4. Excellent electrical properties and good high-temperature insulation, 10 14ω-cm at 25℃ and 103ω-cm at 2000℃. It is the best high-temperature insulating material in ceramics, with breakdown voltage of 3KV/MM and low dielectric loss of 2.5× 65448 Hz. 5, good corrosion resistance and general metals (iron, copper, aluminum, lead, etc. ), rare earth metals, precious metals, semiconductor materials (germanium, silicon, potassium arsenide), glass, molten salt (crystal stone, fluoride, slag), inorganic acid and alkali do not react.
6. The 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 contains B, the impurity content is less than 10PPM, and the content of B 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.
Application 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 purpose
1, release agent for metal molding, lubricant for metal wire drawing.
2. Special electrolytic and resistive materials at high temperature.
3. High-temperature solid lubricants, extrusion anti-wear additives, additives used to produce 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 desiccant 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, high voltage and high frequency electrical and plasma arc insulators.
1 1, packaging material for preventing neutron radiation.
12, boron nitride superhard materials can be made into high-speed cutting tools and drill bits for geological exploration and oil drilling.
13, metallurgical separation ring of continuous casting steel, amorphous iron runner, continuous casting aluminum release agent (various optical glass release agents) 14, various capacitor films, picture tubes, evaporation boats for aluminum plating of displays, etc.
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, cigarette packaging boxes aluminizing, etc.
17. Cosmetics are used as fillers of lipsticks, which are non-toxic, smooth and shiny. They are the best lipsticks in France. Molecular formula: CB4
Molecular weight: 55.25
Si Nuo. : 12069-32-8
Attribute: Density 2.5 1.
Also known as boron tetrachloride. Glossy black crystal. Industrial products are usually in powder form. The density is 2.520g/cm3. The melting point is 2350℃. Boiling point > 3500℃. Soluble in molten alkali. Insoluble in water and acid. Hardness is second only to diamond. The mixture of boric acid, artificial graphite and petroleum coke is carbonized in an electric arc furnace at 1700 ~ 2300℃, cooled, crushed, sieved, washed with hot water for many times, coarsely crushed, acid washed, settled and separated, dried and sieved. It can also be prepared by mixing boron and carbon and reacting at 2200 ~ 2250℃. Widely used in cemented carbide, as grinding materials, as well as the processing of gem materials and the preparation of metal boron compounds. It is also used in atomic reactors.