Particle size distribution measurement from millimeters to nanometers, and from rods to platelets

There are many instruments for particle size distribution (PSD) measurement, each using a particular physical phenomenon to define the size (e.g., sedimentation, laser diffraction). Particle size distribution measurement although important, most people want it done as quickly as possible. This paper will compare rapid methods [laser diffraction and photon correlation spectroscopy (PCS)] with sedimentation techniques and image analysis. Nanometer powders (primary particles 10-50nm) have been studied using, photocentrifuge, PCS, and x-ray disc centrifuge. The median diameters are very consistent for all instruments for narrow size distributions at around 20 nm but a divergence of results for the 50 nm range when distributions are broader Comparison with image analysis for a spherical silica (50 nm) illustrates the accuracy possible in this domain. In the 0.1 to 5 micron range examples showing how the width and size range of the particle size distribution of typical commercial aluminas and calcites, can influence greatly the reported values from different instruments will be presented, The resolution and accuracy of PSD measurement for laser diffraction has been. investigated using spherical glass beads ranging from 70 to 400 mum, sieved into five, fractions. Particle size distributions measured by image analysis are compared with the laser diffraction results. The shape also has a profound effect on the interpretation of data provided by commercial instruments which ordinarily assume a spherical shape. Results for plate and rod like particles will be presented and the most appropriate method for the shapes suggested.