Main Physical, Chemical and Electrochemical Properties of Silicon Carbide

Silicon carbide is a synthetic carbide with a molecular formula of SiC. It is usually formed by silicon dioxide and carbon at a high temperature of 2000°C or higher after electrification. Due to its high hardness, high wear resistance, high corrosion resistance and high-temperature strength, SiC is used in various wear-resistant, corrosion-resistant and high-temperature resistant mechanical parts.

Chemical properties

Oxidation resistance: When silicon carbide is heated to 1300°C in air, a protective layer of silicon dioxide begins to form on its crystal surface. With the thickening of the protective layer, the internal silicon carbide is prevented from being oxidized, which makes the silicon carbide have better oxidation resistance. However, when the temperature reaches 1900K (1627°C) or higher, the silicon dioxide protective film begins to disappear, and the oxidation of silicon carbide intensifies.　　

Acid and alkali resistance: due to the silicon dioxide protective film on its surface, silicon carbide has strong acid resistance.

Physical and mechanical properties

Density: Because the particle densities of different silicon carbide crystal forms are very close, the density of SiC is generally considered to be 3.20 g/mm3. The natural bulk density of the silicon carbide abrasive is between 1.2-1.6 g/mm3, and its value depends on the particle size number, particle size composition and particle shape.

Hardness: The Mohs hardness of silicon carbide is 9.2, the Vickers micro-density hardness is 3000-3300 kg/mm2, and the Knoop hardness is 2670-2815 kg/mm. Simply put, the hardness of SiC is higher than that of corundum in abrasives and second only to diamond, cubic boron nitride and boron carbide.

Thermal conductivity: Silicon carbide products have high thermal conductivity, low thermal expansion coefficient, high thermal shock resistance, and are high-quality refractory materials.

Electrical properties

Industrial silicon carbide is a kind of semiconductor at room temperature, which is impurity conductivity. The resistivity of high-purity silicon carbide decreases with the increase of temperature, and the conductivity of impurity-containing silicon carbide varies according to its impurity. Another electrical property of silicon carbide is electroluminescence, and practical devices have been developed to effectively utilize it.