Synthesis of nanophase silicon, carbon, and silicon carbide powders using a plasma expansion process

Nanophase powders of Si, C, and SiC with narrow size distributions are synthesized by dissociating reactants in a dc are plasma and quenching the hot gases in a subsonic nozzle expansion. The plasma is characterized by calorimetric energy balances and the powders by on-line aerosol measurcment techniques and conventional materials analysis. The measured nozzle quench rate is about 5 × 10⁶ K/s. The generated particles have number mean diameters of about 10 nm or less, with Si forming relatively dense, coalesced particles, while SiC forms highly aggregated particles. Our data suggest that SiC particle formation is initiated by the nucleation of small silicon particles.