From grains to powders: From single particle contact mechanics measurements to bulk powder properties

Methods based on atomic force microscopy have been used to measure adhesion and sliding and rolling friction for single micron-sized particles. Model systems with low surface roughness (silica and gold particles) as well as technical products (carbonyl iron powder (CIP) particles) with less defined surface properties were used. For the model substances no significant dependence of adhesion on load was observed. For the CIP particles, plastic deformation was observed at higher loads. Comparison of the microscopic material parameters obtained for the CIP particles showed good agreement with the corresponding values obtained from Jenike shear cell experiments; this is especially true for the maximal attractive (cohesive) force. Computer simulations indicate that the macroscopic cohesion is primarily correlated to this (microscopic) maximal attractive force