Boron carbide chemical formula B4C. A glossy black crystal with a relative density of 2.52, a melting point of 2350 ℃, and a boiling point above 3500 ℃. Stable in chemical properties, insoluble in water and various acids, and soluble in molten alkali. The hardness is lower than diamond but higher than silicon carbide, with a Mohs hardness of 9.3. Has high capture ability for thermal neutrons, is wear-resistant, and has semiconductor conductivity. The general requirement for product quality is that the content of B4C in abrasive particles should not be less than 95%, and that of nuclear power grade should not be less than 98%. Boron carbide is widely used in the grinding and polishing processes of gemstones due to its excellent performance. Sapphire is the most ideal substrate material for practical applications such as semiconductor GaN/Al2O3 light-emitting diodes (LEDs), large-scale integrated circuit SOI and SOS, and superconducting nanostructured thin films. As an LED substrate, sapphire chips require a high level of surface smoothness, which must be ultra smooth and undamaged. The quality of the device mainly depends on the surface processing technology of the substrate, and grinding is a key link in the sapphire industry. Different abrasives have a significant impact on sapphire grinding and chemical mechanical polishing. At present, boron carbide as a sapphire abrasive has gradually replaced diamond abrasive, greatly reducing the cost of the grinding process.
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