Interaction mechanism between nanoparticles and ultra-smooth surface under effect of cavitation

During the nanoparticle colloid jet polishing process to obtain ultra-smooth surface, cavitation is easy to occur because of the intense fluid turbulence. Cavitation interacts with nanoparticles in the colloid solution, which has a great influence on the processing quality of the ultra-smooth surface. In this paper, the collision between nanoparticles and ultra-smooth surfaces under the micro-jet effect formed by cavitation is studied. Molecular dynamics simulation result shows that the collision of nanoparticles changes the atomic position of the collision region of workpiece, resulting in lattice distortion, coordination number and atomic potential energy increased. The ultrasonic cavitation system is used to prepare the monocrystalline silicon workpiece that effected by nanoparticle colloid cavitation. After the process, the dark spots could be observed on the surface of workpiece by SEM. The dark spots are the traces of the collision between the nanoparticle and workpiece, which verify the molecular dynamics simulation results. XPS detection of the surface of monocrystalline silicon workpiece processed by nanoparticle colloid cavitation has been done and the result is slightly different from the workpiece that have not been processed by cavitation. The difference illustrates that the chemical bonding between nanoparticles and monocrystalline silicon surfaces has formed. The simulation and experimental results show that the cavitation is beneficial to the removal of the material of the workpiece by nanoparticles, but it has an adverse effect on the formation of ultra-smooth surface.