In this study, we synthesized two types of calcium sulfonate complex greases (barium soap and calcium soap) and investigated their physical, rheological, and tribological properties in detail. The test results showed that the evolution of their linear viscoelasticity functions with frequency were quite similar to those of traditional lubricating greases. Moreover, these two calcium sulfonate complex greases had good friction-reducing and antiwear properties at room temperature and at 150 ^°C. In addition, by adding an organic molybdenum compound (MoDTC) to the base greases, we obtained a very low friction coefficient (0.065) for one of the greases (calcium soap) at 400 N and 500 N (maximum Hertzian pressures of 3.47 GPa and 3.74 GPa, respectively) at 150 ^°C. X-ray photoelectron spectroscopy (XPS) analysis showed that the tribofilm was composed of some complex oxide species and CaCO₃ that had formed on the worn surface.

Three kinds of new conductive lubricating greases were prepared using lithium ionic liquids as the base oil and the polytetrafluoroethylene (PTFE) as the thickener. These lithium ionic liquids ([Li(PEG)X]) were obtained by blending lithium salts (LiBF₄, LiPF₆ and LiNTf₂) with poly(ethylene glycol) (PEG) because lithium salts have an extremely high solubility in PEG. The conductivities and contact resistances of the prepared lubricating greases were investigated using the DDSJ-308A conductivity meter and the reciprocating ball-on-disk UMT-2MT sliding tester. In addition, their tribological properties were investigated in detail. Scanning electron microscopy and X-ray photoelectron spectroscopy were employed to explore the friction mechanisms. The results suggest that the prepared lubricating greases have high conductivities and excellent tribological properties. The high conductivities are attributed to ion diffusion or migration of the lithium ionic liquids with an external electric field, and the excellent tribological properties depend on the formation of boundary protective films.