Silicon Carbide (SiC)

Silicon carbide (SiC) is a compound of silicon metalloid and oxygen usually used in the alpha silicon carbide structural form.  SiC is a black, high hardness ceramic that usually is harder than alumina.  Depending on the Impurity additions, silicon carbide is green or black in color. Fully dense silicon carbide can be transparent (Moissanite).  Silicon carbide has found wide application due to its versatility and a relatively low raw material cost. Depending on the purity and density SiC is used for refractory tubes, industrial crucibles, wafer semi-insulating substrates, wear components, refractory cements and abrasives.  Alumina's main drawback is its relatively poor thermal shock resistance compared to materials with lower coefficients of thermal expansion.  Silicon carbide forms a protective SiO2 skin that to prevents further oxidation at very high temperatures in non-reducing atmospheres.  Silicon carbide has relatively high thermal shock resistance compared to other ceramic materials due its low coefficient of thermal expansion combined with high thermal conductivity.