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 precursors and condensation in the gas phase to form nanoparticles. In this study, the influence of reactor parameters including pressure, substrate standoff distance, and precursor concentration on silica particle size are measured. The results indicate that particle size is strongly dependent on standoff distance and precursor concentration, but less dependent on pressure. Furthermore, the particle size is observed to decrease with increasing precursor concentration, which is different from results of previous flame studies where the substrate was absent. Samples taken from near the substrate show a markedly different particle size than those taken from the walls of the chamber, which suggests that some particle trajectories escape the rapid quench zone near the substrate.