Target polishing of KDP crystals by organic acid-ionic liquid-in-oil microemulsions

Chemical polishing is an effective method to remove a subsurface damage layer with the advantages of no mechanical stress and no new subsurface damage. In this paper, we report a target polishing method that employs an anhydrous organic acid-ionic liquid-in-oil (OA-IL/O) microemulsion as the etching solution for chemical polishing of KDP crystals. OA-IL/O microemulsions were prepared with 1-butyl-3-methyl imidazolium bis [(trifluoromethyl) sulfonyl] imide ([Bmim]TF₂N) and bis (trifluoromethane sulfonimide) (TF₂NH) as the internal phase, castor oil as the external phase, TX-100 as the surfactant, and n-butanol as the co-surfactant. TF₂NH irreversibly reacts with KDP when microemulsion micelles driven by Brownian motion collide with the KDP surface. The organic salt products are removed by the ionic liquid in the microemulsion, resulting in the effective elimination of KDP. Moreover, the organic acid-ionic liquid solution will preferentially diffuse to the high points of the KDP surface and react with the KDP to achieve the target polishing. As a new type of water-free surface polishing technology, OA-IL/O microemulsion not only has the advantages of traditional CMP, but also avoids the recrystallization that can occur with water-in-oil microemulsions and achieves target polishing of the KDP crystal.