A review of recent advances of ionic liquids as lubricants for tribological and thermal applications

The novel characteristics of ionic liquids (ILs) led to an improved tribological and thermal performance. This article discusses current progress in developing ILs as neat lubricants or additives in lube oils, with a focus on ILs chemistry, synthesis, miscibility, and other relevant rheological, thermal, and tribological properties at macro to nanoscales. This article also introduces a review of lubrication mechanisms based on the tribofilm formed on the rubbing interfaces owing to tribochemical reactions among the ILs, base oil, and solid bodies, which shows key insights into anti-wear properties. ILs exhibited superior anti-wear properties compared to fully formulated oils. Notably, there was no symmetry between the friction results of ILs and their wear counterpart. Furthermore, the main challenges to further improve ILs performance for tribological applications are highlighted. Eventually, prospects for ILs tribology are suggested, which will guide the development and synthesis of ILs-based lubricants for tribological applications.