Hexagonal boron nitride and its composite materials prepared by hot pressing sintering have excellent high temperature resistance, resistance to metal melt and slag erosion, high thermal conductivity and high electrical insulation, and easy processing performance and high processing accuracy ( (Up to 0.01mm), low density, lubricating, non-toxic, is an ideal high temperature thermal insulation material.

Its main performance:

1. High heat resistance: Oxidation does not begin until 900 ° C in an oxidizing atmosphere. It can be safely used up to 2000 ° C under vacuum, and it does not soften at 2800 ° C in an inert gas; its strength at 1800 ° C is twice that of room temperature

2. High thermal conductivity: The hot-pressed product is 33W / m · k, which is the same as pure iron, and the material with the highest thermal conductivity among ceramic materials above 530 ℃;

3. Low thermal expansion coefficient: The expansion coefficient of 2 × 10-6 is second only to quartz glass and is the smallest among ceramics.

4. Excellent electrical properties: good high temperature insulation, 1014Ω-cm at 25 ° C, and 103Ω-cm at 2000 ° C. It is the best high-temperature insulating material in ceramics, with a breakdown voltage of 3KV / mm. Low dielectric loss, 2 ~ 5 × 10-4 at 108Hz, dielectric constant 4, microwave and infrared transmission;

5. Good corrosion resistance: with general metals (iron, copper, aluminum, lead, etc.), rare earth metals, precious metals, semiconductor materials (germanium, silicon, potassium arsenide,), glass, molten salt (crystal stone, fluorine) Chemical compounds, slag), inorganic acids, alkalis do not react;

6. Low friction coefficient: μ is 0.16, does not increase under high temperature;

7. Machinability: Its hardness is Mohs 2, so it can be processed into parts with high precision by general machining methods, and the processing accuracy can reach 0.01mm.

Based on the above properties, boron nitride and its composite materials have many uses in cutting-edge technologies such as electronics, metallurgy, chemical industry, and aerospace:

1. Utilizing the excellent chemical stability of hexagonal boron nitride ceramics, it can be used as a crucible for smelting and evaporating metals, boats, liquid metal delivery pipes, crucibles for synthesizing GaAs crystals, rocket nozzles, high-power device bases, pipes for melting metals, Pump parts, cast steel molds, etc .;

2. Utilizing the heat and corrosion resistance of hexagonal boron nitride ceramics, high temperature components, rocket combustion chamber linings, spacecraft heat shields, and magnetic current generator corrosion resistant parts can be manufactured;

3. Utilizing the insulation of hexagonal boron nitride ceramics, it can be used for high-voltage high-frequency electrical equipment and plasma arc insulators, insulators for various heaters, heating tube bushings, and high-frequency insulation materials for electric furnaces.

4. Utilizing the high insulation and high thermal conductivity of hexagonal boron nitride ceramics, it can be made into semiconductor component insulation and heat dissipation bottom plates, transformer fillers, and high temperature, high frequency, high voltage insulation and heat dissipation components;

5. Using the heat resistance, corrosion resistance and insulation of hexagonal boron nitride ceramics, it can be made into high-temperature insulating parts of plasma arc and plasma welding tools, thermocouple protection tubes of molten metal, horizontal continuous casting separation rings, etc .;

6. The use of low-frequency loss characteristics can be made into a microwave energy transmission window, using high B content as a semiconductor solid diffusion source.