Effect of chain length on tribological performances of MXene solvent-free nanofluids as additives for water-based lubricants

Covalent solvent-free nanofluids show excellent tribological properties, yet the effect of organic shell chain length on performance remains unclear. This work innovatively synthesized three MXene-based nanofluids (M1000 NFs, M2070 NFs, M3085 NFs) with tuned canopy chain lengths, revealing chain-dependent performance. Short-chain M1000 NFs achieved superior oxidative stability in water through dense surface grafting, maintaining performance over 180 days. As a water-based additive, M3085 NFs with extended chains reduced friction by 74% at 0.25 wt% via an optimized adsorption layer. Wear resistance depended mainly on MXene core concentration rather than chain length. These insights provide key design guidelines for high-performance aqueous MXene nanofluids, particularly addressing the coupled challenges of oxidative degradation and friction control.