Study on tribological properties of oleic acid-modified TiO2 nanoparticle in water

A cis-9-octadecenoic acid (OA) surface-modified TiO2 nanoparticle with average diameter of 30 nm was chemically synthesized. The tribological properties of the prepared OA–TiO2 nanoparticle as an additive in water were evaluated with a four-ball tester. The results show that the OA–TiO2 nanoparticle exhibits good antiwear and friction reduction properties as well as load-carrying capacity. The maximum non-seizure load (PB value) can be raised about 6–10 times when 0.1–1.0% OA–TiO2 nanoparticle was added into water. The rubbed surface after friction tests was investigated with X-ray photoelectron spectroscopy (XPS). The results of XPS analysis indicate that a boundary film mainly composed of TiO2 and oleic acid complex, was formed on the rubbed surface.