Particle size and pore (void) size distribution determination by photomicrographic methods

Abstract

The two different statistical methods that have been recently tested by the authors have been applied to the determination of size distribution of non-spherical, angular common salt (NaCl) particles. Two different techniques were used: in one of them the particles were mounted in oil on a microscope slide, shadow-graphs were prepared, the chord length distribution over the particle images in the photomicrographs were determined using the Q.T.M. and the size distribution of the solid particles back-calculated by the Scheil method. In the other technique a packed bed was formed from the solid particles, the voids were saturated with Wood's metal, photomicrographs were prepared of polished sections of the system, the chord length distribution over the solid particle images in section determined on the Q.T.M., and the particle size distribution back-calculated by the Cahn, Fullman method. The distribution curves obtained compare reasonably well with each other and with the results of standard sieve analysis. The latter of the two techniques could also be used to determine the pore size distribution of porous materials. The pore size distribution obtained by this method could be interpreted as the size distribution of bulges which, if interconnected, are geometrically, similar to particles in a packed bed. Since the standard mercury porosimetry method of pore size distribution measurement gives the distribution of pore volume by pore entry radii whereas the present method gives the distribution of pore space by pore diameters, comparison of the distribution curves obtained by these two different methods sheds additional information on the pore structure.