DETERMINATION OF THICKNESS, ASPECT RATIO AND SIZE DISTRIBUTIONS FOR PLATEY PARTICLES USING SEDIMENTATION FIELD-FLOW FRACTIONATION AND ELECTRON-MICROSCOPY

Sedimentation field-flow fractionation (SdFFF) can be used to prepare fractions of very narrow mass range for electron microscopic (EM) anal ysis. Assuming the particle density is the same for all particles with in that fraction the equivalent spherical diameter for the particles c an be calculated from SdFFF theory. Integration of the micrograph imag e of each particle yields an area measurement which, when used in conj unction with the equivalent spherical particle diameter (from SdFFF), provides information about the particle thickness and aspect ratio. Th us SdFFF-SEM can be used to provide detailed information about clay mo rphology across the particle size distribution of the sample. Three cl ay minerals have been studied using the methodologies outlined in this paper. The aspect ratio for the Purvis School Mine kaolinite ranged f rom 2.8-5.9, for RM30 illite from 11.3-24.3, and for Muloorina illite from 3.1-4.3.