Development of core–shell SiO2@A-TiO2 abrasives and novel photocatalytic chemical machinal polishing for atomic surface of fused silica

It is extremely hard to achieve atomic surface on fused silica with a high material removal rate (MRR). Furthermore, in traditional chemical mechanical polishing (CMP), toxic and corrosive slurries are widely employed. To address these challenges, core–shell SiO2@A-TiO2 abrasives were prepared, and novel photocatalytic CMP was developed. The developed CMP slurry consists of sodium carbonate, hydrogen peroxide, sodium carboxymethylcellulose and deionized water. After CMP, atomic surface with surface roughness Sa of 0.181 nm was achieved at a scanning area of 50 × 50 μm2 and a high MRR of 10.727 μm/h. X-ray diffraction, X-ray photoelectron spectroscopy and Fourier transform infrared were used to elucidate the photocatalytic CMP mechanisms. The developed SiO2@A-TiO2 abrasives could generate electrons and holes irradiated by simulated solar light, producing free radicals (OH–). As a result, OH– combined with Si atoms on the surface of fused silica, forming Si-OH-Si bonds. This constructed interlinkage of slurry and surface of fused silica via SiO2@A-TiO2 abrasives improved synergistic effect between chemical and mechanical functions. The developed core–shell abrasives and photocatalytic CMP suggest new findings to achieve atomic surface for a hard-brittle solid with a high MRR.