There are very few natural silicon carbides, and the industrially used synthetic raw materials, commonly known as corundum, are a typical covalent bonded compound. (1) Properties of silicon carbide: There are two main crystal forms of silicon carbide: b-SiC and a-SiC. b-SiC is a face-centered cubic sphalerite structure with a lattice constant a=0.4359nm. a-SiC is a high-temperature structure of SiC, which belongs to the hexagonal crystal system. It has many variants. The silicon carbide produced by Jinmeng New Materials is a-SiC.
The refractive index of silicon carbide is very high, which is 2.6767~2.6480 under ordinary light. The density of silicon carbide in various crystal forms is close, a-SiC is generally 3.217g/cm3, b-SiC is 3.215g/cm3. Pure silicon carbide It is colorless and transparent, and industrial SiC turns light green or black due to impurities such as free Fe, Si, and C. The hardness of green silicon carbide and black silicon carbide is basically the same at room temperature and high temperature. The thermal expansion coefficient of SiC is not large, and the average thermal expansion coefficient is 4.5×10-6/℃ at 25~1400℃. Silicon carbide has very high thermal conductivity, which is 64.4W/(m·K) at 500°C. SiC is a semiconductor at room temperature.
Silicon carbide has the characteristics of high temperature resistance, wear resistance, erosion resistance, corrosion resistance and light weight. Oxidation of silicon carbide at high temperatures is the main cause of its damage. (2) Synthesis of silicon carbide: the smelting method of Jinmeng new material silicon carbide. The raw materials used for the synthesis of silicon carbide are mainly gangue with SiO2 as the main component. Low-grade silicon carbide can use low-ash anthracite as raw material, and the auxiliary raw materials are Sawdust and table salt.
Many customers are in the process of testing thermal and electrical conductivity, due to the high strength, corrosion resistance, high temperature and wear resistance of Al2O3 and other materials, the stability is not good, so compared with silicon carbide micropowder The application largely meets the usage requirements of some customers.
α-SiC and β-SiC are another embodiment of crystallization and performance according to different production methods. α-SiC is the original block of conventional silicon carbide products currently on the market. It is a crystal transformation product after resistance furnace and high temperature sintering at 1800°C. And β-SiC is a high-tech, high-crystallization, high-purity β-SiC obtained by three production methods of laser method, plasma method and solid phase combination. And there are only a few companies in the world that are currently known to be able to do it.
As a semiconducting material, β-SiC is several times higher than α-Sic. Since β-SiC has a diamond structure as a precision grinding and polishing material, β-SiC has a much higher grinding efficiency than white corundum and α-SiC, and can greatly improve the product finish. .
In fact, it is simpler. At present, β-SiC is a refined silicon carbide product that is close to the crystal phase and diamond structure and has higher functionality than ordinary α-SiC.
