Ceramics-Silikáty 46, (2) 41 - 48 (2002)

The influence of the orientation of oblate particles on volume-weighted particle size distributions (PSD) is demonstrated with an idealized model system. The overall estimate is based on partial "worst case" estimates found by an explicit calculation of selected non-random orientations for disk-shaped particles with an aspect ratio of 10 and a wide-range PSD. According to the simulation results the D₁₀, D₅₀ (median) and D₉₀ values for particle orientations of 60°, 45°, 30° and 0° deviate by less than 17 % from those of the 90° orientation (corresponding to projections normal to the disk plane), whereby the maximum deviation occurs for orientations close to 30°. For quasi-random orientation the deviation is even smaller (approx. 3-7 %). Thus it is shown that, in contrast to widespread belief, the effect of particle orientation on the resulting volume-weighted PSD is for oblate particles small enough to be completely smeared out for purely statistical reasons to within typical errors of measurement of the usual sizing methods.