Experimental investigation of photocatalytic-Fenton composite reaction parameters in polishing of single-crystal SiC using magnetorheological elastomer polishing pads

Single-crystal SiC exhibits excellent properties including wide bandgap, high thermal conductivity and high electron mobility, which enable its extensive applications in new energy vehicles, 5G communication, aerospace and other fields. Nevertheless, its high hardness, superior wear resistance and strong chemical inertness inevitably lead to low machining efficiency and unsatisfactory surface processing quality. In this work, magnetorheological elastomer (MRE) was introduced into chemical mechanical polishing (CMP) system as CMP polishing pad. The TiO 2 particles and CIP@Fe 3 O 4 particles embedded in the MRE were used as catalysts for the photocatalytic-Fenton composite reaction (hereinafter referred to as the composite reaction) to perform oxidation modification on the single-crystal SiC surface, aiming to reduce its processing difficulty and achieve high-quality surface finishing. The influence laws of catalyst parameters (catalyst ratio, CIP@Fe 3 O 4 particle size, TiO 2 particle size) and reaction parameters (light intensity, H 2 O 2 concentration) on the •OH concentration and the polishing effect of single-crystal SiC were investigated. Meanwhile, the effect of the composite reaction on the surface oxidation behavior of SiC and its underlying mechanism were deeply explored. The results show that there is a significant correlation between the •OH concentration and the polishing performance. With the decrease of catalyst ratio and the increase of CIP@Fe 3 O 4 particle size and TiO 2 particle size, both the •OH concentration and material removal rate (MRR) showed a trend of first increasing and then decreasing, while the surface roughness presented a trend of first decreasing and then increasing. With the increase of light intensity and H 2 O 2 concentration, the efficiency of composite reaction was enhanced, the •OH concentration and MRR were increased, and the surface roughness was reduced. When the catalyst ratio was 21:5, the MRR of SiC polished with the proposed MRE polishing pad reached 2966 nm/h, and the surface roughness was as low as Ra 0.202 nm. The electrochemical corrosion test of SiC revealed that the E Corr and I Corr in the composite reaction system reached 0.422 V and 2.25 × 10 −7 A/cm 2 , respectively, indicating that the composite reaction can significantly promote the oxidation of the SiC surface and increase the oxidation rate. The presence of Si O bonds on the SiC surface and the normalized mass fraction of oxygen element reaching 20.49% confirm the formation of SiO 2 oxide layer on the material surface. This study can provide theoretical basis and experimental support for the application of magnetorheological elastomer polishing pads in chemical mechanical polishing of single-crystal SiC.