Surfactant-assisted preparation of Y2O3-stabilized ZrO2 nanoparticles and their tribological performance in mineral and commercial lubricating oils

We report the synthesis and tribological characterization of zirconia (ZrO2) nanoparticles in base mineral oil and commercial formulated lubricating oils. A modified chemical method was applied to prepare nano-sized ZrO2 structurally stabilized with yttria (Y2O3) in a precipitation process with the addition of various surfactants (polyethylene glycol, polyvinyl pyrrolidone, and polyether amine). Characterizations by X-ray diffraction and transmission electron microscopy show that polyether amine facilities the formation of stable ZrO2 with coexisting tetragonal and monoclinic phases and is better in preparing Y2O3-stabilized ZrO2 nanoparticles with a smaller particle size and narrower size distribution compared to the other surfactants used. The friction and anti-wear characteristics, which were tested with a four-ball module, indicate that the as-prepared Y2O3-stabilized ZrO2 nanoparticles perform better in commercial formulated lubricating oils than in the base mineral oil medium, and 0.1-0.5 wt% nanoparticles should be sufficient to achieve good tribological performance in lubricating oils.