A Note on the Misuse of Area Images to Obtain Particle Size Information in Solid-Solid Systems

Abstract

Multiphase solids (slag + matte, metals + inclusions) are frequently sectioned and the areas of the phases visible at the resulting surfaces are obtained using one of a number of microscopic techniques. Number concentrations of particles can be obtained unambiguously from these images. However, misinterpretation of these area distributions as particle size distributions for the dispersed phases arises frequently and in diverse contexts. When particles are binned coarsely and the particles are nearly spherical, the impact of such misinterpretations on mean particle size and interfacial area per unit volume and even relative dispersed phase volume fraction is shown to be small. In other cases the errors can be significant. In all cases, the number fraction of small particles is overstated. Thus, interfacial area per unit volume of dispersed phase tends to be overstated, the mean particle size and relative dispersed phase volume fraction underestimated. In this note, an analytical method for the deconvolution of area distributions for dispersed spherical particles is rehearsed and numerical results for randomly oriented axially-symmetric particles and analogues for disc-like and needle-like particles are presented which illustrate the significance of the impact of such misinterpretations. Other limitations on the interpretation of area distributions are also discussed.