ABSTRACT
This chapter describes the nature of particle motion within bulk powders and particle dispersions in gaseous and liquid media, including the flow, fluidization, and mixing of powders, as well as diffusion and gravitational sedimentation of dispersed systems. Particle sizing techniques may be classified as direct imaging, indirect imaging, physical separation, and charge analysis methods. Fractal analysis is a mathematical tool used to describe the surface morphology and the degree of surface irregularity of a particle as a single parameter, the fractal dimension. Coulombic forces occur between charged particles and an uncharged surface. The charged particle induces an equal and opposite charge on the surface, producing image forces. Particle adhesion is affected by fundamental particle properties, such as particle size and shape and surface roughness, and environmental factors, such as storage duration and humidity. Powder mixing depends on the particle interactions. Random mixing occurs between noninteracting particles, whereas interactive mixing involves particle adhesion.
