Improvement in surface quality of diamond-turned aluminium substrate by using hydrogen peroxide: a molecular dynamics simulation study

Abstract

In this work, the atomic mechanism of chemical treatment on diamond-turned aluminium surface due to aqueous H₂O₂ is investigated using a reactive molecular dynamics simulation (R-MDS). This study is carried out to understand the mechanism of surface quality improvement of a diamond-turned aluminium workpiece due to chemical treatment. Surface quality improvement is focused to analyse the effect of chemical treatment process for improving surface finish, reflectance and chemical stability of the workpiece. It is observed that the diamond-turned surface contains a higher cohesive energy as compared to atomically smooth surfaces. Chemical treatment does more material removal on nano-peaks with respect to the smooth surface, and this helps to reduce the cohesive energy as low as naturally possible. By applying this treatment, the optical quality of the workpiece gets enhanced drastically. R-MDS also reveals that the nano-peaks of diamond turn machining (DTM) surface can further improve surface finish by using the chemical treatment process, and the same is validated by experiments. Experimental data also support that due to the reduction of surface roughness, reflectance increases in a broad band of wavelength. The present work shows that material removal from the nano-peaks of workpiece occurs due to the oxygen radicals generated from H₂O₂, which raise the local temperature, followed by temperature-assisted chemical reaction. When most of the nano-peak atoms are removed, further material removal stops. Experimental results also support the mechanism of such process of chemical treatment. Hence, the diamond turned surface can be further improved beyond the capability of the diamond turning process to cater the need for optics and astronomical mirror at-least one step ahead in the domain of ultra-precision manufacturing.