Study on an antiwear and extreme pressure additive of surface coated LaF₃ nanoparticles in liquid paraffin

A LaF₃ nanoparticle surface coated by organic compounds containing S and P was synthesized by the chemical surface modification method. The particle size and structure were characterized using a transmission electron microscope (TEM) and electron diffraction (ED), their tribological behaviors were evaluated on a four-ball machine. The results showed that LaF3 nanoparticles as an oil additive can strikingly improve the load-carrying capacity and antiwear property of the base oil and had better friction-reduction when compared to that of ZDDP. The rubbed surfaces were investigated by scanning electron microscopy (SEM) and X-ray photoelectron spectroscope (XPS). It can be found that the boundary film on the worn surface was composed of LaF3 nanoparticles depositing film and tribochemical reaction film of the elements of S and P, which contributed to excellent tribological properties of LaF₃ nanoparticle modified by compound containing S and P as an additive in liquid paraffin.