1992 Volume 10 Pages 131-144
Dense and uniform packing of ultra-fine powders, the primary particle size which ranges from 1nm to 0.1 μm, is very difficult because of strong and sparse aggregation. In this paper, the aggregating process of ultra-fine powder is examined by Brownian dynamic methods, and the effects of interaction between the primary particles and the initial concentration on aggregate shape and size is analyzed quantitatively by Fractal dimension and Weibull's distribution function. Furthermore, the packing of aggregates, which are of various shapes and are composed of different numbers of particles, is investigated by computer simulation. The effect of the geometrical characteristics and size distribution of aggregates on the porosity and distribution of micropore diameters in a packed bed is analyzed. When many aggregates consist of hundreds of particles, the porosity exceeds 94%. The porous structure is obtained by bridging between several aggregates. The wide spaces in ultra-fine powder composed by bridging are confirmed experimentally by mercury porosimetry. The effect of shape and size distribution of aggregates on packed bed structures is remarkable in the case of weakly aggregated powder, which means that the number of constituent particles is below 10.
† This report was originally printed in KAGAKU KOGAKU RONBUNSHU 17(4), 837-845 (1991) in Japanese, before being translated into English by KONA Editorial Committee with the permission of the editorial committee of the Soc. Powder Technology, Japan.
