Experimental and simulation study of nanometric surface roughness generated during Magnetorheological finishing of Silicon

Abstract

Silicon Mirrors are essential components for guiding the X-Ray beam and focusing it to a particular location. These mirrors using total internal reflection require super smooth surface finish because X-Ray wavelength is very small, otherwise it suffers from strong scattering. The polishing possibility of silicon mirrors by Magnetorheological finishing process is examined. Magnetorheological finishing (MRF) is a computer-controlled technique that is used in the production of high quality optical lenses. This novel finishing process utilizes polishing slurries based on magneto rheological fluids, whose viscosity changes with the change in magnetic field. In this study, the MRF is used to polish the silicon mirror in order to achieve nanometric surface finish to be used for X-rays applications. The individual effect of parameters like magnetizing current, working gap, rotational speed on surface roughness is investigated. Based on the experimentation, the optimized process parameters are identified. The final surface roughness achieved is as low as 6.4nm. The surface quality is analyzed in terms of arithmetic roughness (Ra) and Scanning Electron Microscopy for uniform evaluation. In order to investigate the physical essence underlying MRF process, the Molecular Dynamics Simulations (MDS) is used. MDS is used to study the atomic-scale removal mechanism of single crystalline silicon in Magneto Rheological Finishing (MRF) process and particular attention is paid to study the effect of gap between the tool and work piece as well as cutting velocity on surface quality.