Hybrid ionic liquid-polyoxometalate nanoadditives for lubricants in electric vehicles

In this work, three ionic liquid cation-polyoxometalate anion hybrid nanoadditives, IL-POMs, namely, [N_1,1,1,12]₃[PW₁₂O₄₀], [C₁₂MIM]₃[PW₁₂O₄₀] and [C₁₂Py]₃[PW₁₂O₄₀], were analyzed as additives for polyalphaolefin 6 (PAO6), where [PW₁₂O₄₀]^3- is a phosphotungstate anion, [N_1,1,1,12]⁺ is dodecyltrimethylammonium, [C₁₂MIM]⁺ is 1-dodecyl-3-methylimidazolium and [C₁₂Py]⁺ is 1-dodecylpyridinium. First, the optimal concentration was determined for the tribological behavior of the nanodispersions containing [N_1,1,1,12]₃[PW₁₂O₄₀] as an additive, which was 0.1 wt%. Second, the tribological performance of the nanodispersions containing 0.1 wt% of each of the three IL-POMs as additives was compared. The nanodispersion PAO6 + 0.1 wt% [N_1,1,1,12]₃[PW₁₂O₄₀] led to the best antifriction and antiwear capabilities with reductions of 13% and 20% in friction coefficient and wear track width, respectively, compared to those of PAO6. Finally, the ionic liquid trihexyltetradecylphosphonium bis(2-ethylhexyl)phosphate, IL1, showed a synergistic effect when used as an additive together with the [N_1,1,1,12]₃[PW₁₂O₄₀] hybrid nanomaterial. Thus, reductions of 23% in friction and 87% in wear track transversal area were found when using PAO6 + 0.1 wt% [N_1,1,1,12]₃[PW₁₂O₄₀] + 1 wt% IL1 as a lubricant instead of neat PAO6. The additives at these concentrations do not significantly modified the density and viscosity of the base oil. The electrical conductivities of the nanodispersion PAO6 + 0.1 wt% [N_1,1,1,12]₃[PW₁₂O₄₀] + 1 wt% IL1 fall within the dissipative range, with a relative percentage increase of around 1800% with respect to neat PAO6.