Analysis of multiscale material removal mechanism in nanoparticle jet polishing

Abstract

Nanoparticle jet polishing (NJP) is an ultra-smooth surface polishing technology based on elastic material removal, which can obtain atomic-scale smooth surface. It is helpful for the wide application of NJP to research the action process of integrated physical and chemical in the material removal and accurately predict the material removal profile. Considering the lack of material removal model for NJP, a multiscale contact area analysis model is proposed in this paper. Based on Hertz contact theory and the kinetic energy theorem, the total contact area between each particle and workpiece is derived, and the time-dependent contact radius and horizontal sliding friction are considered. The size of the particle contact area determines its contribution to material removal. The energy required to remove a single atom apart from the workpiece surface is calculated by Molecular Dynamics. The sources of energy needed to remove atom and the effect of each energy source are analyzed by Computational Fluid Dynamics. The model quantitatively links the non-uniform contact of each particle with the workpiece and the atom removal on the workpiece surface. By combining the contact area model with the experimental research, the number of hydroxyl groups with effective chemisorption between particle surface and workpiece surface in unit area is determined, and the material removal profile is predicted. Finally, the reliability of the contact area model is verified by a series of experiments according to different fluid pressure and slurry concentration. And the influence of experimental parameters on material removal rate is explained based on this model. This research not only contributes to deeply understanding the material removal process of NJP, and lays a theoretical foundation for improving the material removal rate, but also is expected to lay a theoretical reference for polishing methods of material removal in elastic region.