Synergy between two protic ionic liquids for improving the antiwear property of glycerol aqueous solution

Two protic ionic liquids (PILs) were prepared and investigated on the tribological behavior of their different combinations in the glycerol-water mixture. Synergy between both PILs can remarkably enhance its antiwear property. Further, the tribological behavior of the optimal combination was explored considering different factors including concentration, temperature and load. All the concentrations demonstrate promising antiwear properties, though a 0.5% dose moderately outperforms other doses. The increase of temperature and load is favorable for the lubricating ability. Based on worn surface analyses and molecular dynamic simulations, the synergistic mechanism between both PILs as lubricant additives is ascribed to the coexistence of the mixed adsorption layers and the tribofilms containing sp(2) bonded carbon, FeS and orthophosphate.