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 quenchin g the hot gases in a subsonic nozzle expansion. The plasma is characte rized by calorimetric energy balances and the powders by on-line aeros ol measurement techniques and conventional materials analysis. The mea sured nozzle quench rate is about 5 x 10(6) K/s. The generated particl es have number mean diameters of about 10 nm or less, with Si forming relatively dense, coalesced particles, while SIC forms highly aggregat ed particles. Our data suggest that SiC particle formation is initiate d by the nucleation of small silicon