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    The Material characteristics of silicon carbide
    Hits:   Date:2020-07-02  
    Silicon carbide has stable chemical properties, high thermal conductivity, small thermal expansion coefficient, and good wear resistance. In addition to being used as an abrasive, there are many other uses, such as: applying silicon carbide powder to a turbine wheel or cylinder block by a special process The inner wall can improve its wear resistance and extend the service life by 1 to 2 times; the advanced refractory materials used to make it are heat-resistant shock, small size, light weight and high strength, and good energy saving effect. Low-grade silicon carbide (containing about 85% of SiC) is an excellent deoxidizer. It can accelerate the steel-making speed, and facilitate the control of chemical composition and improve the quality of steel. In addition, silicon carbide is also widely used to make silicon carbide rods for electric heating elements.

    The hardness of silicon carbide is very large, Mohs hardness is 9.5, second only to the world's hardest diamond (10), has excellent thermal conductivity, is a semiconductor, it can resist oxidation at high temperature.

    There are at least 70 crystalline forms of silicon carbide. α-Silicon Carbide is the most common kind of homogenous material, which is formed at a high temperature above 2000 °C and has a hexagonal crystal structure (like wurtzite). β-Silicon Carbide, a cubic structure, similar to diamond, is generated below 2000 °C. The structure is shown in the figure on the page. Although in the application of heterogeneous catalyst supports, it is noticeable because it has a higher surface area per unit than the α-type, while another type of silicon carbide, μ-silicon carbide, is the most stable and has a more pleasant sound when collided. But as of today, these two types have no commercial application.

    Due to its specific gravity of 3.2g/cm3 and high sublimation temperature (about 2700 °C), silicon carbide is very suitable as a raw material for bearings or high-temperature furnaces. It will not melt under any pressure that has been reached, and has a fairly low chemical activity. Because of its high thermal conductivity, high collapse electric field strength and high maximum 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 of its high sublimation points make it practical for heating metals.

    Pure silicon carbide is colorless, and the industrially produced brown to black is due to impurities containing iron. The rainbow-like luster on the crystal is caused by the protective layer of silica on the surface.