Silicon carbide, due to its stable chemical properties, high thermal conductivity, low coefficient of thermal expansion, and excellent wear resistance, has many applications besides being used as an abrasive. For example, coating the inner wall of turbine impellers or cylinder blocks with silicon carbide powder using a special process can improve their wear resistance and extend their service life by 1-2 times. High-grade refractory materials made from silicon carbide are thermally shock resistant, small in size, lightweight, high in strength, and energy-efficient. Low-grade silicon carbide (containing approximately 85% SiC) is an excellent deoxidizer, which can accelerate steelmaking and facilitate control of chemical composition, thus improving steel quality. Furthermore, silicon carbide is widely used in the manufacture of silicon carbide heating elements.
Silicon carbide has a very high hardness, with a Mohs hardness of 9.5, second only to diamond (10), the hardest stone in the world. It possesses excellent thermal conductivity, is a semiconductor, and is resistant to oxidation at high temperatures.
Silicon carbide has at least 70 crystalline forms. α-Silicon carbide is the most common type of allomorphous material, formed at temperatures above 2000 °C, and has a hexagonal crystal structure (similar to wurtzite). β-Silicon carbide, with a cubic crystal structure, is similar to diamond [13] and is formed at temperatures below 2000 °C. β-Silicon carbide has attracted much attention in the application of heterogeneous catalyst supports due to its higher specific surface area than α-Silicon carbide. There is another type of silicon carbide, μ-Silicon carbide, which is the most stable and produces a pleasant sound when struck. However, neither of these two types of silicon carbide has been commercially applied to date.
