Scattering efficiency of clusters composed by aggregated spheres

We present a detailed study of the variation of the average scattering cross section of various aggregates of titanium dioxide crystallites as a function of their sizes and shapes. To perform the analysis, we use a recursive T-matrix algorithm that we developed. We show how the aggregation phenomenon can tremendously decrease the local scattering properties of a white paint film and consequently affects its hiding power. We also compare the results with the equivalent spherical volume approximation which is used in particle size analysis using static or dynamic light-scattering methods. We show how the equivalent volume approximation used in those methods should be handled with care. (C) 2003 Elsevier Science Ltd. All rights reserved.