Silicon carbide is also called "emery powder" or "refractory sand." The usual manufacturing process of SiC is to combine silica sand, tar (or coke), woodchip (and salt when manufacturing green SiC) and other materials in an electric resistance furnace at a high temperature. Silicon carbide is usually divided into two categories, the black SiC and the green SiC, both having a hexagonal crystal structure, a density of 3.2 -3.25g/cm³ and microhardness of 2840-3320kg/mm2. The black SiC is manufactured with silica sand, tar and high quality silica as main materials in an electric resistance furnace at a high temperature. It is of hardness between corundum and diamond, mechanical robustness higher than corundum, crisp and sharp. The green SiC is manufactured with tar and high quality silica as main material, salt as additive, and in an electric resistance furnace at a high temperature. The hardness of green SiC is also between corundum and diamond, and mechanical robustness is higher than corundum.
Silicon carbide is of high hardness, good thermal and electrical conductivity, and is oxidation resistant under high temperature. It can be used as abrasive material or be made into abrasive tools such as abrasive wheel, sharpening stone, grinding unit, abrasive segment and so on. It can also be used as high temperature material and deoxidant in metallurgy. There are four major fields where silicon carbide is in general application: functional ceramics, high grade refractory, abrasive and metallurgy materials. And high-purity silicon carbide can further be used in semi-conductor and silicon carbide fibre production. Due to its unique physical and electrical properties, silicon carbide has become the best semi-conductor in some applications such as short wavelength photoelectric cell, high temperature, radiation resistant element and high frequency, high power component. Its major advantages are as following:
1.Wide energy level(eV)
4H-SiC: 3.26 6H-Sic: 3.03 GaAs: 1.43 Si: 1.12
2.High thermal conduct efficiency(W/cm‧K@RT)
4H-SiC: 3.0-3.8 6H-SiC: 3.0-3.8 GaAs: 0.5 Si: 1.5
3.High disruptive field intensity
4H-SiC: 2.2x106 6H-SiC: 2.4x106 GaAs: 3x105 Si: 2.5x105
4.High saturated electron drift velocity(cm/sec @E 2x105V/cm)
4H-SiC: 2.0x107 6H-SiC: 2.0x107 GaAs: 1.0x10 Si: 1.0x107
With its wide energy level, the electronic components made of SiC are able to work under extremely high temperatures, can resist voltage and electric field 7 times larger than silicon and gallium arsenide, and is therefore especially good material in manufacturing high pressure and high power components, like high pressure diode. In addition, SiC is good thermal conductor with better conductivity than any other semi-conduct materials. These excellent characteristics have made SiC widely used in both industry and military fields.