The influences of technological parameters on the ultraviolet photocatalytic reaction rate and photocatalysis-assisted polishing effect for SiC

Abstract

Abstract At first, aiming at ultraviolet (UV) photocatalysis-assisted polishing of single-crystal 6H-SiC (silicon carbide), the particle size and zeta potential of colloidal silica abrasives on photocatalytic reaction conditions were detected. By doing so, it was guaranteed that colloidal silica abrasives retained their stability with the assistance of photocatalysis. Afterward, the effects of various factors (including light intensity, H2O2 concentration, TiO2 concentration, and pH) on the reaction rate of UV photocatalysis were explored and an orthogonal experiment was conducted on the four factors. The test results showed that H2O2 concentration and light intensity delivered the most significant and the least influences on the rate of photocatalytic reaction, respectively. As the rate of photocatalytic reaction increased, the material removal rate (MRR) increased while the surface roughness Ra generally decreased. In terms of the influence on MRR, the four factors were, in descending order: H2O2 concentration, pH, light intensity, and TiO2 concentration; as for the influence on surface roughness Ra, the four factors were, in descending order: pH, H2O2 concentration, TiO2 concentration, and light intensity. The difference in rank of the four factors arose because MRR was mainly affected by the rate of photocatalytic reaction while surface quality (roughness) was synchronously influenced by the reaction rate and the stability of abrasives. At a light intensity at 1000 mW/cm2, H2O2 concentration of 4.5 vol%, TiO2 concentration of 3 g/L, and a pH of 11, the optimal polished surface can be attained, with a surface roughness Ra of 0.423 nm.