The application of nanoparticles in tribology has received considerable attention in recent years. In this paper, we described the preparation of Ni nanoparticles in microemulsions of sodium dodecyl sulphate (SDS)/isopentanol/cyclohexane/water and their tribological performance as additives in oils. The size of these nanoparticles is about 10 nm, and their shape is spherical. The four-ball test results indicate that Ni nanoparticles are potential additives for lubricating oils, and the tribological performance of lubricating oils can be improved significantly by dispersing Ni nanoparticles in oils. The maximum non-seizure load (PB) has been increased by 67 percent as compared with background oil. The wear scar diameter has been reduced from 0.71 mm to 0.49 mm. The relative percentage in friction coefficient has decreased 26 percent. The tribological mechanism is that a deposit film in the contacting regions was formed, which prevented the direct contact of rubbing surfaces and greatly reduced the frictional force between the contacting surfaces.
