Combustion synthesis of ultra-fine SiC powders in low pressure N2-atmosphere

Ultra fine SiC nano-powders (100–300 nm) of high purity were successfully produced by combustion of a powder mixture of Si and C, with the addition of poly-tetra-fluoro-ethylene (PTFE) as a chemical stimulator, in a moderately pressurized nitrogen atmosphere (1–10 MPa). The experimental results showed that with the aid of mechanical activation of the starting powders, a small amount of PTFE (1.5 wt%) can effectively stimulate the reaction between Si and C. Both the experimental results and thermodynamic calculations indicate that the formation of Si₃N₄ plays a key role in the process. The optimum conditions for producing the aforementioned SiC fine powders were 1.5 wt% PTFE, 1 MPa N₂ pressure and no addition of diluents of SiC powder.