A cost-effective process for large-scale production of submicron SiC by combustion synthesis

In this paper, a cost-effective process was developed for large-scale production of submicron SiC by the combustion synthesis. Large and thin reactant samples (120 x 120 x 6 mm(3)) were prepared from ground reactant powders of silicon and carbon black. In order to reduce the cost of the expensive silicon powders, different particle sizes were used. Prior to the cold press of the reactant sample, a small amount of PVA (polyvinyl alcohol) slurry, which served as a binder, was added into the mixed reactant powders, The reactant samples were combusted by a custom-built oxy-acetylene torch in air. The averaged reaction yield throughout the product was about 94%. If the molar ratio between carbon black and silicon was increased from I to 1.1, the averaged yield raised to about 97%. Further increase of the molar ratio could not raise the yield. The product consisted of beta-SiC with a trace of alpha-SiC. The grain size of SiC was around 0.2 mum and the morphology showed that SiC particles were aggregated. In some cases, the aggregated SiC particles were sintered together. Particle size distribution of SiC powders before and after grinding were both narrow. The averaged particle size of both SiC powders were approximately 0.25 mum. Using different particle sizes of starting silicon powders all resulted in the similar combustion results. The questions, why submicron SiC powders were produced and why starting particle sizes of silicon powders did not change the combustion products were discussed. Further reductions of process cost and proposals of continuous production tines were also addressed. (C) 2002 Elsevier Science B.V. All rights reserved.