Microwave plasma modification-assisted shear-thickening polishing of single-crystal silicon carbide

Abstract

This study addressed existing limitations on the efficiency and efficacy of SiC processing by introducing an innovative microwave plasma modification-assisted shear-thickening polishing (MPM-STP) technology. First, the modification mechanism and effects of microwave plasma irradiation on the surface of a single-crystal SiC workpiece were explored. The formation of SiO₂ product by plasma modification was confirmed by X-ray photoelectron spectroscopy, and nanoindentation testing indicated an accompanying significant reduction in the hardness and elastic modulus of the SiC from 37.04 GPa to 4.71 GPa and from 504.57 GPa to 68.96 GPa, respectively, enhancing its processability. A systematic investigation of the changes in workpiece surface morphology under various microwave irradiation times, power levels, and distances revealed that a longer irradiation time and higher power level intensified the surface modification effect, and the irradiation distance had a crucial influence on the uniformity of the modified film, which could be optimized through precise adjustment of the irradiation parameters. Next, plasma-modified SiC workpieces were subjected to shear-thickening polishing using a CeO₂ abrasive, resulting in the complete removal of the modified film within 15 min and a substantial reduction in surface roughness R_a from 9.74 nm to 0.31 nm, indicating significantly improved surface quality. Finally, the results of nanoscratch experiments conducted on the surfaces of SiC workpieces before and after plasma modification indicated the transformation of the material removal mode from brittle fracture to plastic removal, which is crucial for improving processing efficiency and surface quality. The successful construction of a surface modification model for single-crystal SiC processed by MPM-STP in this study opens a new path for the high-precision machining of SiC materials.