Preparation and tribological properties of unmodified and oleic acid-modified CuS nanorods as lubricating oil additives

Unmodified and oleic acid-modified CuS nanorods were prepared by water bath and hydrothermal method. The prepared CuS nanorods were characterized by X-ray diffraction and transmission electron microscope. The tribological properties of both types of CuS nanorods as additives in liquid paraffin (LP) were investigated using a vertical universal friction and wear testing machine. The addition of unmodified and oleic acid-modified CuS nanorods was found to significantly reduce the friction coefficient and wear rate of pins by increasing the surface area and addition concentration of CuS nanorod additives. The addition of oleic acid-modified CuS nanorod showed higher anti-wear properties than those of unmodified CuS nanorods. The prominent tribological performances of CuS nanorods additives were attributed to the formation of complete and uniform tribo-film，which is confirmed by the EDS analyses of tested worn surfaces of pins.