A Study of Particle Growth Using Light Scattering and Local Sampling in Flame Synthesis of Nano Particles

The growth of silica particles in coflow diffusion flames has been studied experimentally using light scattering and local thermophoretic sampling techniques. The number densities and volume fractions of both aggregates and spherical particles have been determined calculated by a novel method of using the scattering cross section measured from 90° light scattering with the combination of particle sizes and morphology measured from the localized sampling and TEM image analysis under the assumption of monodisperse distribution of primary particles in an aggregate. Rayleigh-Debye-Gans and Mie theories have been applied to the calculations for fractal aggregates and spherical particles, respectively. Of particular interests are the effects of carrier gas flow rates on the evolution of silica particles and the roles of radial heat and H2O diffusion have been studied when using N2 or O2 as a carrier gas.