Physical and chemical properties of silicon carbide

Material characteristics
Due to its stable chemical properties, high thermal conductivity, low coefficient of thermal expansion, and good wear resistance, silicon carbide has many other uses besides being used as an abrasive. For example, coating silicon carbide powder on the inner wall of the turbine impeller or cylinder body with a special process can improve its wear resistance and extend its service life by 1~2 times; The advanced refractory material used to make it is heat-resistant, small in size, light in weight, and high in strength, with good energy-saving effects. Low grade silicon carbide (containing about 85% SiC) is an excellent deoxidizer, which can accelerate steelmaking speed, facilitate chemical composition control, and improve steel quality. In addition, silicon carbide is also widely used in the production of silicon carbide rods for electric heating components.
Silicon carbide has a high hardness, with a Mohs hardness of 9.5, second only to the world's hardest diamond (grade 10), and has excellent thermal conductivity. It is a semiconductor that can resist oxidation at high temperatures.

Silicon carbide has at least 70 crystalline forms. α- Silicon carbide is the most common homomorph, which is formed at a high temperature higher than 2000 ° C and has a hexagonal crystal system crystal structure (similar to wurtzite). β- Silicon carbide, with a cubic crystal structure similar to diamonds, is generated at temperatures below 2000 ° C, as shown in the attached figure on the page. Although in the application of heterogeneous catalyst support, it has advantages over α The higher the unit surface area, the more eye-catching, while another type of silicon carbide, μ- Silicon carbide is the most stable and has a pleasant sound when colliding, but to this day, these two forms have not yet been commercially applied.
Due to its specific gravity of 3.2g/cm3 and high sublimation temperature (approximately 2700 ° C), silicon carbide is very suitable as a raw material for bearings or high-temperature furnaces. Under any achievable pressure, it will not melt and has relatively low chemical activity. Due to its high thermal conductivity, high collapse electric field strength, and high maximum current density, many people have tried to replace silicon in the application of semiconductor high-power components. In addition, it has a strong coupling effect with microwave radiation, and all its high sublimation points make it practical for heating metals.
Pure silicon carbide is colorless, while industrial brown to black is due to impurities containing iron. The rainbow like luster on the crystal is caused by the protective layer of silica produced on its surface.