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

Abstract

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.