Composite Process of Diamond Smoothing Based on Surface Modification Promotion

Diamonds are used in various industries due to their excellent performance, but the roughness of synthetic diamonds remains a challenge. This article proposes a composite process for polishing chemical vapor deposition diamonds. The first step involves achieving dynamic friction polishing using a heat-assisted robot, reducing the diamond’s root mean square roughness (Rq) from the original 101 nm to 10. By using a combination of heat assistance and robotic processing, the first step of polishing can be completed quickly. Subsequently, a polishing liquid is formulated using K₂FeO₄, deionized water, glacial acetic acid, and W0.25 diamond abrasive for chemical-mechanical polishing (CMP), ultimately achieving a further reduction in Rq to 3.9 nm. By examining the surface structure and composition of diamonds, a comprehensive analysis of the composite polishing process has been conducted. The experiment demonstrates that in the initial processing step, both mechanical and thermal assistance aid in the graphitization process on the diamond surface. In the subsequent step, CMP facilitates the conversion of C–C bonds on the diamond surface into C–OH, C–O–C, and C=O bonds, thereby reducing bond energy and further smoothing the diamond surface. This represents the first integration of dynamic friction polishing and CMP processes, offering a novel approach to diamond polishing.