Robust Macroscale Superlubricity in Humid Air via Designing Amorphous DLC/Crystalline TMDs Friction Pair
Superlubricity, a cutting-edge concept, has the potential to drive the Fourth Industrial Revolution giving its near-zero energy consumption, but the challenge is how to achieve it in humid air with chemical activity and at macroscale surfaces with unavoidable defects. Here, a novel principle involving the amorphous/crystalline friction pair based on the cognition that tribochemical interaction sites originate from grain boundary defect locations is proposed to achieve macroscale superlubricity in humid air. The absence of grain boundaries in amorphous diamond-like carbon (DLC) significantly reduces chemical interaction during the sliding process. This is supported by experimental observations of priority oxidation at the grain boundaries. Results indicate DLC versus MoS 2 friction pair has weakened chemical interaction and less humid insensitivity compared to the MoS 2 versus MoS 2 pair, even increasing the contact area. Theoretical simulation suggests that DLC versus MoS 2 pair eliminates the cross-linking of friction interlayers induced by the enrichment of H 2 O molecules at MoS 2 defects. The robust superlubricity is achieved for the typical friction pair of DLC versus MoS 2 in air (RH≤25%) at macroscopic contact pressure (1.1 GPa) with friction coefficient in 10 −3 magnitude and extra-long anti-wear life (more than 2 × 10 5 cycles), which is of significance for the industrialization of superlubricity.
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