Combustion synthesis of high purity SiC powder by radio-frequency heating

High purity silicon carbide (SiC) powder was produced via combustion synthesis by radio frequency (RF) heating. The reaction described here was involved in four stages: preheating, initial combustion reaction, product formation and cooling. Significantly, the initial combustion reaction started from a low ignition temperature (Ti) in the range of 1160 °C–1200 °C, subsequently the reaction proceeded under RF heating. The C/Si ratio, reaction temperature and reaction time had a large influence on the resultant SiC powder. Particularly, based on the comparison of the ignition temperature and the reaction degree under different C/Si ratios, it was firstly proposed that the C/Si ratio with 1:1 was not the optimal condition for the initial combustion reaction. Moreover, with the increase of reaction temperature and the reaction time, the phase transitions of SiC from 3C to 6H and from 6H to 15R were found, respectively. The SiC grains grow with the reaction time due to the successive reaction processes including formation, decomposition, fusion and reformation.