Achieving ultrafast superlubricity with layered double hydroxides

Layered double hydroxides (LDHs) have the potential to be superlubricated materials due to their strong adsorption effect and weak internal interaction. However, obtaining stable superlubricity during the ultrafast time (< 10 s) is still a challenge. Here, we demonstrated macroscale superlubricity based on LDHs of multiple metal ions at high surface roughness, achieving superlow friction coefficients (0.006) and ultrafast wearing-in time (< 7 s), which mainly originated from tribochemical reactions and the formation of nanostructured adsorption layers. Through cross-sectional analysis and density functional theory, we revealed the properties of the protective tribofilm to achieve ultrafast superlubricity. LDHs strongly adsorbed on the surface of the bearing steel, and the sliding interface transformed into a heterogeneous interface between the polytetrafluoroethylene and LDH, leading to macroscale superlubricity. These findings demonstrate that tribochemical treatment of surfaces produces tribofilm that effectively reduces wearing-in time and promotes ultralow friction.