Collect. Czech. Chem. Commun. 1979, 44, 361-373

Dependence of chemical inhomogeneity of granular materials on the size and shape of particles

Pavel Boháček

Physical Institute, Czechoslovak Academy of Sciences, 180 00 Prague 8


Avenues have been explored of possible improvement of inhomogeneity of a granular material using the relationships defining the structure of chemical inhomogeneity of compact and granular materials and a proper choice of particle size, shape and orientation in the original compact material. The results apply generally to granular materials prepared from compact (monolitic) samples. It is apparent though that considerations regarding optimum shape and orientation of the particles concern mostly metallic materials in the form of cutting chips while do not pertain to powdered materials prepared by grinding. The used method consisted of the assessment of the dependence of individual components of inhomogeneity on particle size for various shapes and orientations. There were essentially three types of dependences found: Non-periodic components of inhomogeneity of the granular material depend on particle size and/or shape only slightly; periodic components diminish starting from a certain value with growing volume of the particle. The regression component increases with the particle's volume. The contradicting character of the two latter types of dependences pointed at the possibility of existence of a minimum (apart from the trivial case of V = 0) on the course of the dependence of the overall variance of inhomogeneity of the granular material versus particle volume. This minimum corresponds to the sought optimum particle volume. Position of this minimum and hence the optimum volume of the particle depend generally on the shape of the particle and its orientation within the material.