Surface functionalized-mos2 nanofluids as high temperature lubricant additives
There is an increasing and urgent need in Europe and globally for effective and robust high temperature (HT) lubricant additives in critical industrial applications. Combining synergistically the exceptional oil solubility of organic polymers and the excellent tribological behaviour of MoS2 nanoparticles (NPs), polymer functionalized-MoS2 NPs with good dispersion stability will be designed and synthesized as candidates for HT lubricant additives. In addition, to suppress MoS2 oxidation under HT, which would cause high friction and wear, carbon nanomaterials (CNMs) will be covalently combined with MoS2 NPs to improve the retention of MoS2 on the frictional surfaces and prevent oxidation during rubbing. In this project, MoS2 NPs will be functionalized by two methods: 1) Immobilization of organic polymer on the surface of MoS2 NPs using non-covalent and covalent approaches. The organic polymers including oil-soluble poly-(lauryl methacrylate) (PLMA), polyalkylene glycol (PEG), and hyperbranched poly(3-ethyl-3-hydroxymethyloxetane) PEHO; 2) MoS2 NPs growing on the surface of organic polymer modified-CNMs with covalent bonds. The polymers connecting CNMs and MoS2 NPs are novel PEHO and PEG derivatives with lipoic acid (LA) and nitrilotriacetic acid (NTA) terminals. The properties of the grafted polymers on MoS2 NPs and CNMs will be analyzed. The dispersion stability of surface functionalization MoS2 NPs will be assessed by SAXS/SANS, as well as cryo-TEM, SEM, DLS, and ξ- potential measurements. The surface force apparatus (SFA) will be used for mechanistic understanding of how such NPs mediate friction, with the macroscopic HT tribological properties of the NP dispersions investigated using tribometer. The correlation between the NP physicochemical properties and their efficacy in lubrication will be assessed. The wear mechanism of surface functionalized-MoS2 NPs as friction reduction and antiwear (AW) additives in lubricating oils will be explored by XPS and SEM-EDS.