A Molecular Dynamics Study on the Tribological Performance of Imidazolium-Based Ionic Liquids Mixed with Oil in Comparison to Pure Liquids

The purpose of this work is to propose an advanced lubricant model of ILs used as additives to conventional oil. All-atoms molecular dynamics simulations are used to investigate the structure and tribology of oxidatively stable pure imidazolium-based ionic liquids (ILs), branched alkane low friction oil, and a mixture of ILs and oil confined between iron surfaces. Equilibrium and shear simulations are performed at a temperature of 450 K and undergo different applied loads and shear velocities to mimic engine operations. Density profiles reveal the formation of layered structures at the interface. The intensity and number of the density peaks vary according to the composition of the system and the applied pressure. Velocity profiles reveal the presence of no-slip conditions in the pure ILs system and very high slip for the oil. The presence of a stable IL layer at the surface of the mixed lubricant fully reduces the slip of oil. Overall, the mixture displays lower friction in comparison to pure ILs. The formed corrosion protective anion layer on the metal surface makes the mixture a potential candidate for a new generation of high-performance lubricants.