Corrosive and toxic solutions are normally employed to polish sapphire wafers, which easily cause environmental pollution. Applying green polishing techniques to obtain an ultrasmooth sapphire surface that is scratch-free and has low damage at high polishing efficiency is a great challenge. In this paper, novel diamond/SiO₂ composite abrasives were successfully synthesized by a simplified sol-gel strategy. The prepared composite abrasives were used in the semi-fixed polishing technology of sapphire wafers, where the polishing slurry contains only deionized water and no other chemicals during the whole polishing process, effectively avoiding environmental pollution. The experimental results showed that diamond/SiO₂ composite abrasives exhibited excellent polishing performance, along with a 27.2% decrease in surface roughness, and the material removal rate was increased by more than 8.8% compared with pure diamond. Furthermore, through characterizations of polished sapphire surfaces and wear debris, the chemical action mechanism of composite abrasives was investigated, which confirmed the solid-state reaction between the SiO₂ shell and the sapphire surface. Finally, applying the elastic-plastic contact model revealed that the reduction of indentation depth and the synergistic effect of chemical corrosion and mechanical removal are the keys to improving polishing performance.

This study addresses the critical challenge of precise control over active abrasive particles in magnetorheological polishing (MRP) through innovative core–shell particle engineering. A sol–gel synthesized CIP@SiO₂ magnetic composite abrasive with controlled SiO₂ encapsulation (20 nm shell thickness) was developed using tetraethyl orthosilicate (TEOS) as the silicon precursor, demonstrating significant advantages in optical-grade fused silica finishing. Systematic polishing experiments reveal that the core–shell architecture achieves a remarkable 20.16% improvement in surface quality (Ra = 1.03 nm) compared to conventional CIP/SiO₂ mixed abrasives, with notably reduced surface defects despite a modest 8–12% decrease in material removal rate. Through synergistic analysis combining elastic microcontact mechanics modeling and molecular dynamics simulations, we establish that the SiO₂ shell mediates stress distribution at tool–workpiece interfaces, effectively suppressing deep subsurface damage while maintaining nano-scale material removal efficiency. The time-dependent performance analysis further demonstrates that extended polishing durations with CIP@SiO₂ composites progressively eliminate mid-spatial frequency errors without introducing new surface artifacts. These findings provide fundamental insights into designed abrasive architectures for precision finishing applications requiring sub-nanometer surface integrity control.

To realize the processing demands of the sapphire wafer surface with scratch-free and nano-scale roughness by mechanical polishing, a novel flexible polishing plate was developed by using soft unsaturated resin. The surface characteristics, material removal rate, and residual stress of the sapphire wafer after the flexible polishing process have been compared with those of the sapphire wafer after the rigid polishing process. Both theoretical and simulation analysis results show that the abrasive particles in the flexible polishing exhibit an apparent yielding effect during the polishing course, which contributes to the achievement of plastic flow removal for the wafer surface. The experimental results show that the surface roughness and subsurface damage of the sapphire wafer polished by the flexible polishing process can be decreased by 18.7% and 57.3%, respectively, compared with those of the sapphire wafer polished by the rigid polishing process.

Polycrystalline diamond (PCD) has broad application prospects in semiconductors, optical windows and other advanced fields. Nevertheless, its ultrahigh hardness and chemical inertness pose significant challenges for achieving high-quality surface planarization. Although conventional mechanical lapping is widely adopted, it still suffers from poor surface quality and a lack of theoretical guidance for process parameter selection. This study presents a systematic experimental and simulation investigation on both rough and fine lapping of PCD, focusing on tool selection and process optimization. In the rough lapping stage, three types of fixed diamond abrasive discs with resin, bronze, and vitrified bonds were compared. The soft and tough resin-bonded disc yields the best performance, reducing surface roughness Ra from 420 nm to 106 nm. In the fine lapping stage, three metallic discs—Cu, Fe, and WC-Co—were evaluated. The high-stiffness WC-Co disc achieves the best results, with an Ra of 11.2 nm under conditions of 0.45 MPa and 600 r/min. Molecular dynamics (MD) simulations further reveal that increasing lapping pressure significantly enhances the material removal rate but concurrently aggravates subsurface damage (SSD), while the effect of speed is considerably smaller. Therefore, pressure emerges as the key parameter that requires balanced optimization in the fine lapping process.