Electrostatic interaction of dust particles to solid surfaces

Particles’ adhesion to surfaces is an essential aspect in almost all fields of scientific endeavor. In some sectors, such as semiconductor manufacturing, particle adhesion to surfaces can create a short circuit hazard. Whereas in some industries, such as pharmaceuticals, particle-to-particle adhesion, in particular, is to be avoided to maintain powder processibility. On the other hand, particle adhesion to surfaces can be desirable for some industries, for example, in xerography, where toner particles should strongly adhere to the paper for better print quality. The interaction between a particle and a surface is complex and involves several adhesion forces and energies. Most studies consider the van der Waals adhesion force as the leading force when a solid particle interacts with a solid surface in a dry atmosphere and ignore the electrostatic adhesion force. The consideration of the dominant van der Waals force assumes that the particles and surface are perfectly smooth. When micron size, high surface roughness particles interact with a rough surface, van der Waals adhesion force decreases significantly, whereas electrostatic adhesion force increases and can dominate the adhesion process. Hence for micron-size particles with natural morphologies, electrostatic adhesion force cannot be ignored. The limited studies that address electrostatic adhesion are primarily based on force measuring techniques, controlling electrostatic adhesion force using different schemes, or limited to 1-2 particle sizes. No electrostatic stick-rebound adhesion model exists to predict the charged particles' behavior near a surface for a range of micron-size particles. The research presented in this thesis aims to address the electrostatic component of the adhesion mechanism. An electrostatic stick-rebound particle adhesion model, based on the energy conservation method of a charged particle interacting with a surface, was developed and applied to a range of micron-size particles. This newly developed theoretical model was implemented in a commercial computational fluid dynamics (CFD) software by customizing and enhancing the general-purpose programming of the CFD software using a user-defined function. An experimental procedure and novel adhesion test equipment were designed to obtain experimental results for the adhesion tests. Finally, the numerical results were compared with the experimental results to validate the model.