Ceramics-Silikáty 46 (2) 41-48 (2002)

AN ESTIMATE OF ORIENTATION EFFECTS ON THE RESULTS OF SIZE DISTRIBUTION MEASUREMENTS FOR OBLATE PARTICLES

W. Pabst, J. Mikač, E. Gregorová, J. Havrda

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.
 

Keywords: Particle size distribution, Oblate particles, Laser diffraction