Preparation and tribological properties of surface-modified nano-Y2O3 as additive in liquid paraffin

Surface-modified nano-Y2O3 was prepared by a coupling-grafting method with vinyl methylerichlorosilane and methyl methacrylate as the coupling agent and grafting agent, respectively. The prepared samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), transmission electron micrograph (TEM) and thermal gravimetric analysis (TGA). The tribological properties of the surface-modified nano-Y2O3 as additive in liquid paraffin were evaluated with a four-ball tester. The results show that the nano-Y2O3 keeps its original crystalline structure after surface modification, and the modified nano-Y2O3 forms a core–shell structure with an average particle size of 24.5 nm. The maximum non-seizure load (PB value) and sintered load (PD value) increase by 25% and 26.9%, respectively, when compared with those of liquid paraffin, and the wear scar diameter (WSD) also decrease by 21% when 0.10% surface-modified nano-Y2O3 was added. The protective inorganic–organic film formed by nano-Y2O3 and organic modifiers plays an important role in the improved tribological properties of liquid paraffin.