Tribological Behavior and Antiwear Mechanism of Layered Double Hydroxides Nanoparticles as Lubricant Additive

The tribological performance of Zn/Mg/Al-CO3 layered double hydroxides(LDHs)as a lubricant additive in base oil was evaluated at different loads and rotational speeds by a four-ball friction tester.The worn surfaces were analyzed by scanning electron microscope equipped with energy dispersive X-ray spectrometer(EDS)and X-ray photoelectron spectroscope(XPS),respectively.The results show that the synthesized Zn/Mg/Al-CO32-LDHs have a typical hexagonal lamellar structure and the chemical formula is Zn0.37Mg0.27Al0.36(OH)2(CO3)0.18·0.31H2 O.After the surface modification,the adsorption on the surface of LDHs with oleic acid molecules occurs.The LDHs in base oil possess the superior friction reducing and antiwear properties at a great load(i.e.,200--400N)and an appropriate rotational speed.According to the EDS and XPS analysis,the tribofilm consisting of oxides,sulfide,graphite and organic compounds is formed on the rubbed surface,which plays an important role in the friction and wear reduction.Besides,the polishing/third body effects of the nanoparticles also improve the tribological properties of lubricating oil.