Double hybrid lubricant additives consisting of a phosphonium ionic liquid and graphene nanoplatelets/hexagonal boron nitride nanoparticles

Tribological performance of polyalphaolefin 32, PAO, is investigated by adding two nanomaterials (graphene nanoplatelets, GnP, and hexagonal boron nitride nanoparticles, h-BN) and an ionic liquid ([P6,6,6,14][DEHP], IL1, [P2,4,4,4][DEP], IL2, or [P6,6,6,14][(iC8)2PO2], IL3). Designed double hybrid nanodispersions are PAO/1 wt% ILX/0.05 wt% GnP/0.1 wt% h-BN (X = 1, 2 or 3). The best anti-friction behavior corresponds to PAO/IL3/GnP/h-BN (40% reduction compared to that achieved with PAO). Anti-wear behavior is similar for the three double hybrid nanodispersions. Roughness of the worn surface tested with PAO is higher than that obtained for each of the nanodispersions. Tribo-film formation and repair effect on worn surfaces due to ILs and nanoparticles are revealed. Some positive synergies were found between each IL and GnP/h-BN as hybrid PAO additives.