Influence of the Particle Size Distribution on the flow behaviour of fine powders

Some results are presented of investigations on the flow behaviour of very fine α‐alumina powders having different particle size distributions. Shear tests were performed in a translation shear cell. The humidity was in the range 0.3 < p D / p SD < 0.6 in order to ensure the formation of adsorbed water layers only and to exclude capillary condensation. In the region of adsorbed layer bondings, the flow behaviour of very fine powders deteriorates in comparison with regions where no adsorption layers exist. An extrapolation of the unconfined yield strength for very low consolidation stresses results in an approximately constant value for different particle size distributions. In contrast, the slope of the linear function σ c = f (σ 1 ) increases with decreasing particle size up to a certain limit. For narrow particle size distributions, there is a pronounced decrease in the bulk density with decreasing particle size. Further, the bulk density is strongly influenced by the width of the distribution.