Particle-Surface Interactions: Charge Transfer, Energy Loss, Resuspension, and Deagglomeration

As an introduction to the 1993 symposium on particlesurface interactions, the nearly 20 years of research on that topic at Berkeley is reviewed. Four main processes are covered-electrical charge transfer between particles and surfaces during impaction, particle energy loss and adhesion to surfaces in impaction, particle resuspension induced by particle impaction, and deagglomeration of particles by impaction. All of these processes are strongly dependent on the physical and chemical condition of the surfaces. Electrical charge transfer is particularly sensitive to the surface condition and can be used to test methods of surface preparation. Contact charging depends on the contact area and its time dependence and can therefore be used to test dynamic models of impaction. The elastic limit is exceeded in most materials, even near the critical velocity for particle bounce. At high impact velocities, it is necessary to take into account the dependence of the yield velocity on the rate of stress application. More experimental work is needed to improve understanding of the impaction of particles on surfaces, including nonnormal incidence and rough surfaces. Theoretical models are needed which are more general and which take into account all the sources of energy loss. The topics of resuspension and deagglomeration by particle impaction are still in the early stages of exploration.