Preparation of Cu@SiO 2 composite nanoparticle and its tribological properties as water‐based lubricant additive

In this paper, to solve the problem that di‐ n ‐hexadecyldithiophosphate (DDP)‐modified Cu nanoparticles initially used as oil‐based lubricant additive cannot be directly used in water‐based lubricants, we adopt a water‐in‐oil reverse micro‐emulsion method to incorporate hydrophobic Cu nanoparticles into silica spheres for obtaining water‐dispersible Cu@SiO 2 nanoparticles. The effects of reaction conditions on the morphology and microstructure of Cu@SiO 2 nanoparticles were investigated. Furthermore, the tribological properties of the as‐prepared Cu@SiO 2 nanoparticles as a lubricant additive in distilled water were investigated with a UMT‐2MT tribometer. Results indicate that the as‐prepared Cu@SiO 2 nanoparticles exhibit good dispersion stability and antioxidant ability in distilled water. Besides, Cu@SiO 2 nanoparticles can significantly improve the tribological properties of distilled water, which is attributed to the formation of a protective and lubricious film consisting of Cu, FeS and SiO 2 on the rubbed steel surface.