Experimental Study on Abrasive-Free Polishing for KDP Crystal

Abrasive-free polishing (AFP) has been developed for processing of soft, hygroscopic KH 2 PO 4 (KDP) crystal according to its deliquescence property. A new nonaqueous abrasive-free slurry, composed of water, dodecanol, and Triton X-100, is designed for the AFP process. In this slurry, the function of water, which is enveloped into surfactant micelles and has no direct contact with KDP crystal in the absence of polishing pressure, is to dissolve KDP surface material in the AFP. The experiments show that the material removal rate (MRR) is nonlinearly dependent on polishing pressure and platen speed; MRR as high as 700 nm min -1 at certain polishing condition and a scratch-free polished KDP surface with root-mean-square roughness lower than 2 nm are achieved by the AFP process. Moreover, the repeat utilization times of the slurry are experimentally determined in KDP AFP With a relatively high removal rate and a smooth surface.