Particle size control during flat flame synthesis of nanophase oxide powders

Combustion Flame - Chemical Vapor Condensation (CF-CVC) is currently under investigation as a candidate for large-scale production of non-agglomerated oxide nanopowders. This process involves controlled pyrolysis of precursor s and condensation in the gas phase to form nanoparticles. In this study, t he influence of reactor parameters including pressure, substrate standoff d istance, and precursor concentration on silica particle size are measured. The results indicate that particle size is strongly dependent on standoff d istance and precursor concentration, but less dependent on pressure. Furthe rmore, the particle size is observed to decrease with increasing precursor concentration, which is different from results of previous flame studies wh ere the substrate was absent. Samples taken from near the substrate show a markedly different particle size than those taken from the walls of the cha mber, which suggests that same particle trajectories escape the rapid quenc h zone near the substrate. (C) 1999 Acta Metallurgica Inc.