Mechanism and experimental study of photoelectro-Fenton composite magnetorheological polishing

The utilisation of chemical-assisted methods is considered an effective approach for enhancing the efficiency of magnetorheological polishing (MRP) and surface quality of optoelectronic wafers. However, these methods may result in corrosion of the magnetorheological components, thereby complicating the oxidation of next-generation optoelectronic wafers. To address this challenge and ensure both efficient chemical oxidation and stable mechanical removal ability in chemical-assisted MRP (CMRP), a novel technique was proposed, termed photoelectro-Fenton composite MRP (PEMRP). This method involves the application of an electric field to decrease the probability of extinction of the photo-generated electron-hole pairs, thereby augmenting the <middle dot>OH generation rate. Additionally, a light field was utilised to decompose the iron flocculent produced by the electric Fenton system into Fe2+ ions, while enhancing the regeneration rate of H2O2 to maintain the stability of the electrochemical reaction. Moreover, carbonyl iron particles (CIPs) were employed to electrocatalytically ionise Fe2+ ions and convert Fe3+ ions into Fe2+. Analysis of the changes in the polishing slurry components and polishing experiments conducted under varying external fields revealed that Fe2+ depletion was rapidly induced by a single electric field, leading to an increase in the Fe3+ concentration and the generation of iron flocs. Conversely, under a single light field, the surface-temperature of the workpiece increased, potentially causing an iron oxide layer to adhere to the surface, thereby hindering material removal. However, under the influence of the photoelectric composite field, a synergistic chemical effect was induced by the combination of CIPs and TiO2, resulting in an efficient Fe2+ regeneration rate (the post-experiment Fe2+ concentration increased by 220.32 %, with Fe2+ comprising 93 % compared to the initial 80 %). Consequently, the highest <middle dot>OH generation rate was achieved under these conditions (the degradation rate of methyl orange stabilised at 96.8 % within 10 min), along with improved polishing efficacy (the material removal rate increased by 70.77 % (to 13.32 mg/h) and the surface roughness decreased by 30.29 % (to 4.35 nm)).