Measurement of aggregates' size distribution by angular light scattering

Abstract

A novel method is introduced for in situ determination of the size distribution of submicronic fractal aggregate particles by unique measurement of angular scattering of light. This method relies on the dependence of a new defined function Rg⋆ on the polydispersity of the aggregates' size distribution. The function Rg⋆ is then interpreted by the use of iso-level charts to determine the parameters of the log-normal soot size distribution. The main advantage of this method is its independence of the particle optical properties and primary sphere diameter. Moreover, except for the knowledge of fractal dimension, this method does not require any additional measurement. It is validated on monodisperse particles selected by a differential mobility analyzer and polydisperse soot from ethylene diffusion flame whose size distribution is independently determined by Transmission Electron Microscopy. Finally, the size distribution of soot generated by a commercial apparatus is measured by the proposed method and the comparison to that given by a commercial granulometer shows a good agreement.