The effect of carbon sources and activative additive on the formation of SiC powder in combustion reaction

Silicon carbide was synthesized by self-propagating high-temperature synthesis process using highly exothermic mixture [Mg+(C2F4)n] as an activative additive and silicon, carbon elements as starting raw materials. Silicon carbide was synthesized by apparently different reaction mechanism due to the addition of the activative additives. Especially with 25 wt.% additive, the reaction product was found to be a best quality. About using the species of carbon, it was observed that the fine carbon black and activated carbon show better reactivity than graphite which has biggest particle size. With change of the molar ratio on silicon versus carbon, the optimum is 1/2 (above the stoichiometric ratio), and finally the impurity MgF2 in the products was entirely removed by leaching process at 10 vol.% (HNO3+HF)+90% water for 4 h.