文摘
Oleylamine (OM) and maleic anhydride dodecyl ester (MADE, synthesized at our laboratory) were adopted as the surface modifiers to prepare OM/MADE-capped tungsten disulfide (WS<sub>2sub>) nanoparticles. An X-ray diffractometer and a transmission electron microscope were performed to analyze the microstructure and phase ingredients of the OM/MADE-capped WS<sub>2sub> nanoparticles. Moreover, a four-ball friction and wear tester and a reciprocating tribometer were employed to evaluate the tribological properties of the surface-capped WS<sub>2sub> nanoparticles as the lubricant additive in diisooctylsebacate (DIOS) from room temperature to 150 °C. The morphology of the worn steel surfaces and wear scars and their chemical states were investigated with a scanning electron microscope, three-dimensional profilometry, and an X-ray photoelectron spectroscope. Results show that OM-capped WS<sub>2sub> nanoparticles nearly have no effect on the tribological properties of the DIOS base oil. The OM/MADE-capped WS<sub>2sub> nanoparticles added in the same base stock at a concentration of 2.0% (mass fraction), however, exhibit good dispersibility and result in greatly improved tribological properties. The reason lies in that, after surface-capping by MADE containing polar group and OM containing coordination group, the OM/MADE-capped WS<sub>2sub> particulates added in the base oil are well adsorbed on the sliding surfaces of the steel–steel contact to afford a chemisorption film with a low shear force. At the same time, OM/MADE-capped WS<sub>2sub> nanoparticles as the additive in DIOS base oil take part in tribochemical reactions to form tribofilm composed of WO<sub>3sub> and iron oxides on sliding surfaces, which also contributes to reducing the friction and wear of the steel sliding contact.