Material properties of silicon carbide

What I bring you today is the knowledge about the material properties of silicon carbide. I hope it will be helpful to you.
Due to its stable chemical properties, high thermal conductivity, small thermal expansion coefficient and good wear resistance, silicon carbide has many other uses besides abrasives. For example, coating silicon carbide powder on the inner wall of turbine impeller or cylinder block by special process can improve its wear resistance and prolong its service life by 1-2 times; the refractory material used for manufacturing has heat shock resistance, small volume and light weight It has high strength and good energy saving effect. Low grade silicon carbide (containing about 85% SiC) is a good deoxidizer. It can accelerate the speed of steelmaking, control the chemical composition and improve the quality of steel. In addition, silicon carbide is also widely used in the production of electric heating elements.
The hardness of SiC is very high, with Mohs hardness of 9.5, second only to the world's hard diamond (Grade 10). It has excellent thermal conductivity and is a kind of semiconductor. It can resist oxidation at high temperature.
There are at least 70 crystalline forms of SiC. α - SiC is a kind of common isomorphism, which is formed at high temperature above 2000 ° C, and has hexagonal crystal structure (like fibrous zinc ore). β - SiC, cubic crystal structure, similar to diamond, is formed at lower than 2000 ° C. The structure is shown in the attached page. Although the application of heterogeneous catalyst support has attracted much attention due to its higher unit surface area than the α - type catalyst support, it has not been commercially used until now.
Because of its specific gravity of 3.2g/cm3 and high sublimation temperature (about 2700 ° C), SiC is suitable for bearing or high temperature furnace. It does not melt at any pressure that has been achieved and has a fairly low chemical activity. Because of its high thermal conductivity, high breakdown electric field strength and high current density, many people try 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 rising points make it practical for heating metal.
Pure silicon carbide is colorless, while brown to black in industrial production is due to impure iron. The iridescent luster of the crystal is due to the silica protective layer on its surface.