Ultra-precision diamond finishing of reaction-sintered silicon carbide enhanced by vibration-assisted photocatalytic oxidation

Abstract

RS-SiC faces limitations in surface accuracy with conventional finishing processes due to its high mechanical hardness and multiphase nature. In this study, vibration-assisted photocatalytic oxidation is introduced to enhance the efficiency and precision of RS-SiC diamond polishing. By utilizing the photocatalytic reaction, the hard heterogeneous SiC phase and Si phase on the RS-SiC surface are transformed into a "softer" homogeneous oxide layer that can be removed easily. The introduction of vibration increases the relative velocity between the workpiece and the abrasive and prevents the aggregation of the photocatalyst, thus improving polishing efficiency. By reducing the abrasive size to the nanometer scale, the boundary between the Si phase and SiC phase can be smoothed out to further improve the workpiece surface finish. Using TiO2 as the photocatalyst, H2O2 as the oxidant, 25 nm diamond as the abrasive, and introducing vibration, an ultra-smooth surface with a surface roughness of 0.195 nm in Ra is obtained by the finishing method proposed in this paper. The proposed photocatalysis/vibration-assisted finishing approach offers a novel method for ultra-smooth polishing reaction-sintered silicon carbide.