(120h) Predicting Bulk Scale Properties of Surface Modified Fine Powders From Particle Scale Interactions

Packing or porosity is a fundamental property of solid particulates systems and is of prime importance to many industries which handle or process such material.  In the case of fine dry particles, attractive van der Waals forces are dominant and can result in high cohesion among particles and poor bulk scale powder properties such as high porosity.  This study investigates the effect of van der Waals force on porosity of powder beds consisting of fine cohesive particles (5 μm − 223 μm).  Nano-dry coating is utilized to modify the surface roughness of particles in order to further elucidate the effect of the van der Waals force on porosity.  Results conclude that nano-dry coating significantly reduces the van der Waals force resulting in improved porosity.  The granular bond number, defined as the ratio of the van der Waals force to particle weight was also shown to accurately predict porosity.  A subsequent theoretical investigation determined the effect of surface modification, specifically the size, surface energy, and surface area coverage of asperities on the porosity.  Further investigation showed that the surface roughness of non-surface modified particles may be poorly defined and may lead to erroneous calculation of inter-particle forces and ultimately the erroneous determination of bulk scale properties such as porosity.  Therefore, in addition to dry coating being a useful process to improve powder properties such as porosity, dry coating can be used to define surface properties to accurately predict bulk level powder properties from particle scale interactions defined by the granular bond number.