Surfactant-assisted preparation of Y 2 O 3 -stabilized ZrO 2 nanoparticles and their tribological performance in mineral and commercial lubricating oils

We report the synthesis and tribological characterization of zirconia (ZrO 2 ) nanoparticles in base mineral oil and commercial formulated lubricating oils. A modified chemical method was applied to prepare nano-sized ZrO 2 structurally stabilized with yttria (Y 2 O 3 ) 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 ZrO 2 with coexisting tetragonal and monoclinic phases and is better in preparing Y 2 O 3 -stabilized ZrO 2 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 Y 2 O 3 -stabilized ZrO 2 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.