In Situ Transition of Amorphous Carbon to Graphite-like Structures Using MXene as a Template for Fast and Long-Lasting Macrosuperlubricity

Achieving fast and long-lasting superlubricity in two-dimensional (2D) materials under high-stress conditions is challenging due to their susceptibility to structural deformations, limited load-bearing capacity, oxidation, and thermal degradation. This study introduces an innovative strategy by utilizing a composite of MXene and H-DLC, where, under high-stress conditions, H-DLC acts as a preferential energy-absorbing phase. MXene serves as a template to rapidly and continuously transform the absorbed energy into graphene-like structures, forming an in situ heterogeneous MXene/graphene-like interface. This process achieves long-lasting macroscopic superlubricity. Friction tests indicate that, under high-stress conditions (∼1.5 GPa Hertz pressure), the coefficient of friction (CoF) of the composite films rapidly decreases to macroscopic superluberic regimes of ∼0.003, with a friction lifespan more than ten times that of the original H-DLC films. In-depth experimental research and tribology-focused molecular dynamics simulations have shown that carbon atoms diffusing from decomposed H-DLC form graphene-like structures under high contact stress, which then evolve into MXene/graphene-like heterostructures. Molecular dynamics simulations reveal that the formation of this heterostructure involves a transition from sp³ to sp² carbon structures, accompanied by significant energy absorption. Our research presents the lowest CoF achieved by MXene or MXene/H-DLC nanocomposite so far.