Particle size and shape characterization of kaolins comparison of settling methods and laser diffraction

It is well known that grain size distributions of clayey raw materials determined by sedimentation methods differ significantly from grain size distributions measured with laser diffractometers due to the anisometric shapes of the particles. Investigation on commercial Czech kaolins by XRD and SEM revealed that the differences of the grain size distributions can be attributed to different mineral contents of the fractions and varying habiti of the kaolinite. It is shown that a numerical analysis of the development of shape with grain size ("SSD-curve") can translate between the grain size determination methods. The shape of those SSD-curves is regular and offers the possibility to evaluate the phase content of the kaolins.