Classification of silicon carbide

Usually classified according to the content of silicon carbide, the higher the content, the higher the purity, the better its physical properties. In general, the content of 95%-98% is a grade, the content of more than 98% is a super grade, the content of 80%-94% is a second grade, the content of about 70% is a third grade, the higher the content and purity of silicon carbide, the greater the value.

Chemical composition: The main impurities are: free silicon (F.Si), which is partly dissolved in silicon carbide crystals, and partly exists in a metallic state with other metal impurities (iron, aluminum, calcium).

Free silicon dioxide (F.IO2) is usually present on the crystal surface, mostly due to smelting silicon carbide resistance

During the cooling process of the furnace, silicon carbide is oxidized and formed. Under normal circumstances, the surface of the green silicon carbide crystal block is free

Silicon, the content of silicon dioxide is about 0.6%, when the silica in the ingredient is too much, silicon dioxide will evaporate and coagulate

Gathered on the surface of silicon carbide crystal, white fluff.

Carbon: (C), when the ratio of carbon is excessive, the carbon particles in the obvious free state are seen. Iron, aluminum, calcium, magnesium due to the high temperature of the products in the furnace and the reducing atmosphere, these impurities in the crystal block are mostly in the alloy state or carbide state.

Chemical composition of silicon carbide abrasive; With the change of abrasive particle size fluctuate slightly, the finer the particle size, the lower the mechanical strength. B: Why is that? Impurities come out)

Chemical properties: High temperature resistance, good oxidation resistance.

Physical properties: between corundum and diamond, high hardness, wear resistance, finer particle size, higher mechanical strength, crushing resistance, toughness.

Electrical conductivity: industrial silicon carbide is a kind of semiconductor, but with the different content of various impurities, the electrical conductivity also changes, containing more aluminum conductivity significantly increases, although the electric field strength increases rapidly, and has the characteristics of nonlinear change. This property of silicon carbide is used to make lightning arrester valve plates.

The resistivity of silicon carbide changes with the change of temperature, but in a certain temperature range and the resistance of the metal temperature characteristics are opposite, with the temperature rises to a certain value, the peak value, continue to increase the temperature, the conductivity will decline.