Superlubricity of water-based lubricants

Superlubricity is a hot research area in tribology that is closely linked to energy dissipation. In this chapter, we show that the liquid superlubricity phenomena can be achieved with various types of water-based lubricants in the point contact conditions, including acid-based solutions, ionic liquids, and surfactant chemistries. The mechanism of liquid superlubricity from phosphoric acid solution to mixture of polyhydroxy alcohol and acid was reviewed, which could be attributed to the formation of a hydrogen-bond network on the Stern layer that is induced by the attached hydrogen ions. Then, the superlubricity achieved with ionic liquids is introduced, which was mainly due to the tribochemical reaction between the anion and surfaces. Finally, the superlubricity achieved by surfactant solutions at the nanoscale was introduced.