Sulfuric Acid Etching for Surface Modification and Improved Polishing of Magnesium Aluminate Spinel

Abstract

Magnesium aluminate spinel is a material with high optical transparency and great potential for optical applications. However, its high hardness, high strength and chemical inertness make obtaining the required surface quality quickly through traditional processing a challenge. Existing assisted machining methods are complicated and costly, which limits their application to high-efficiency and ultra-precision manufacturing. In this study, etching was employed as a polishing preprocess owing to its obvious advantages of simplicity, practicality and low cost. Sulfuric acid was applied to etching spinel, and the influences of the etching temperature and time on the surface morphology and mechanical properties of the spinel were evaluated. Surface analytical techniques were performed to clarify the mechanism for improved polishing. Experimental results indicated that sulfuric acid etching significantly reduced the surface hardness. The surface quality and efficiency were significantly improved with the etching pretreatment compared with traditional chemical mechanical polishing. Thus, the proposed method of sulfuric acid etching-assisted polishing can reduce the difficulty of spinel machining to realize the high-efficiency and precision manufacturing for a wider range of applications.