KINETICS OF CARBOTHERMAL REDUCTION SYNTHESIS OF BETA SILICON-CARBIDE

Carbothermal reduction kinetics to synthesize SiC is studied under conditions of high carbon/silica precursor heating rates (10(5) K/s) and minimized reaction times (s) over a wide temperature range (1,848 less-than-or-equal-to T less-than-or-equal-to 2,273 K). The reaction mechanism includes rapid formation of a gaseous SiO intermediate. Further carbon reduction of the SiO to SiC is reaction-rate-controlling. Carbon crystallite diameter, d, has a substantial influence on the rate of reaction and the size of synthesized SiC. Fractional oxide conversion, X, can be described by a contracting volume shrinking core model: k = 1 - (1 - X)1/3/t = k0/d exp(-E/RT) where k0 = 27.4 m/s and E = 382 +/- 34 kJ/mol.