The Tribological Mechanism of Cerium Oxide Nanoparticles as Lubricant Additive of Poly-Alpha Olefin

Oleylamine (hereinafter referred to as OM)-modified CeO 2 nanoparticles were synthesized by a one-pot pyrolysis method. The tribological properties of the as-prepared CeO 2 nanoparticles as the lubricant additive in poly-alpha olefin (PAO) were investigated with a four-ball machine, and their lubricating mechanism was discussed in relation to worn surface analyses by SEM, EDS, and XPS. Findings indicate that these nanoparticles exhibit good dispersibility as well as excellent anti-wear ability in PAO. This is because OM-modified CeO 2 nanoparticles can catalyze the oxidation of metallic Fe to form ferrite oxide-containing tribo-film. Under the condition of ASTM D2266-2001, the same lowest WDS was obtained at the concentration of 0.2 wt% and 1.8 wt%. When the concentration of CeO 2 is 0.2 wt%, a compact catalytic oxidation tribo-film is formed, which has more outstanding long-term anti-wear ability. When 1.8 wt% CeO 2 is added, the tribo-film formed is the combination of catalytic oxidation film and ceria deposition film, which has more significant bearing capacity.