Synergistic Lubrication Effect of Solvent-Free MXene@Fe3O4 Nanofluids as Efficient Lubricants

Solvent-free nanofluids were synthesized by grafting an organic oligomer shell onto the nanomaterial core, demonstrating significant liquid flow behavior at room temperature without any solvents. The synergistic effect within the solid–liquid combination found in solvent-free nanofluids positions them as potential lubricant candidates. In this study, solvent-free MXene@Fe3O4 nanofluids (MXene@Fe3O4 NFs) were successfully synthesized by loading Fe3O4 nanoparticles in situ onto MXene nanosheets, followed by covalent grafting with a silane coupling agent and a flexible long-chain polyetheramine. Its magnetic response properties were then assessed, highlighting its potential for recyclability. The tribological performance of MXene@Fe3O4 NFs as lubricants was examined under varying operating conditions with a focus on the morphology and chemical composition of the worn surface to elucidate the lubrication mechanism. The results reveal that MXene@Fe3O4 NFs, compared to MXene NFs and Fe3O4 NFs, exhibit optimal tribological performance. Additionally, even under severe loads, temperatures, or frequencies, MXene@Fe3O4 NFs show superior friction-reduction and wear-resistant properties. This phenomenon can be attributed to the fluidity endowed by the organic shell layer coupled with the synergistic tribological effects between MXene nanosheets and Fe3O4 nanoparticles. As solid–liquid lubricants with magnetic responsivity, MXene@Fe3O4 NFs present an effective strategy for high-performance lubricants synthesis.