Preparation, Dispersion and Tribological Properties of Oleophilic Lanthanum Hydroxide/Graphene Oxide Nanocomposites

Lanthanum hydroxide/graphene oxide nanocomposites(La（OH）;/GO) modified by octadecylamine（OCA）, oleylamine（OLA）, and polyvinylpyrrolidone（PVP） were prepared, respectively, as the base oil additives. The dispersion stability of different modified La（OH）;/GO in base oil was studied by means of centrifugation. The tribological properties of oleophilic La（OH）;/GO in base oil were investigated using an UMT ball-disc tribometer. The micro-morphology and chemical composition of the worn surface were characterized by 3 D laser microscope, SEM, EDS, XPS, and Raman spectroscopy, respectively. The wettability performance of the worn surface was also studied based on the contact angle measurements. The test results showed that the OLA-La（OH）;/GO nanocomposites had good dispersion stability in base oil. The anti-wear performance of base oil was improved significantly by the addition of OLA-La（OH）;/GO nanocomposites. The characterizations of worn surface showed that the OLA-La（OH）;/GO nanocomposites could form the metal oxide and graphene protective films effectively on the friction interface and thus increased the oil wettability of the worn surface, thereby resulting in an improved wear resistance.