Influence of burner scale-up on characteristics of flame-synthesized titania and silica nanoparticles

The influence of geometrically-similar upscaling of a laboratory diffusion flame burner on the morphology, specific surface area and phase composition of titania and silica nanoparticles has been investigated. For these two materials systems, two flame configurations were studied using both a laboratory-size and an upscaled burner. Independent of the burner size, smaller and more aggregated particles form in the double diffusion flame, while spherical particles result from the single diffusion flame. The titania and silica powders produced in the upscaled burner have a lower specific surface area and are less homogeneous, despite being synthesized at the same overall flame stoichiometry and gas outlet velocities as used with the laboratory burner. These results can be explained by the increase in flame height, which causes the residence time of the growing particles in the high-temperature flame to increase. The larger single diffusion flame stems from the longer radial diffusion paths between the reactant gases in the upscaled burner.