Hydrophilicity-Dependent Distinct Frictional Behaviors of Different Modified MXene Nanosheets

MXene nanosheets are promising to be ultrathin solid lubricant or interface solving the friction and wear problems of miniaturized equipment. Here, the frictional behaviors and adhesive properties of the Ti3C2, F-Ti3C2, and TMA-Ti3C2 nanosheets were explored by atomic force microscope for the first time. The nanofrictional behavior of TMA-Ti3C2 was significantly different from that of Ti3C2 and F-Ti3C2. The friction of TMA-Ti3C2 increased slightly and then decreased as the load decreased, leading to the appearance of a negative friction factor; the frictions of Ti3C2 and F-Ti3C2 decreased with decreasing load, resulting in positive friction factors. Meanwhile, because the surface of TMA-Ti3C2 was more hydrophilic than that of Ti3C2 and F-Ti3C2, the friction and adhesion of TMA-Ti3C2 were greater than those of Ti3C2 and F-Ti3C2. It indicated that the surface properties played an important role in the adhesion and friction. Hence, adjusting the surface properties of MXene nanosheets will provide a new direction for designing solid lubricants and nanointerfaces in micro- and nanoelectromechanical systems.