The Evolution\nof Nanoscale Third Body Layer Revealed\nby Graphite Structural Superlubric Contact

Revealing the evolution of nanoscale\nthird bodies confined\nbetween\nsliding surfaces is essential to understanding the friction and electrical\nproperties for solid contacts. Here, with graphite/graphite contacts\nin structural superlubricity, a state of no wear and ultralow friction,\nwe <i>in situ</i> reveal the morphological evolution of\na third body layer introduced by air through measuring friction and\nconductance during cyclic hold–slide tests. The directional\ntransport of confined molecules causes apparent elastic deformation\nof the third body layer, leading to local graphite/graphite direct\ncontact. Together with a proposed quantum tunneling effective thickness\n(<i>d</i><sub>eff</sub>) model, a constant volume of third\nbodies with a sub-nm thickness is observed. Our work provides a feasible\napproach to investigate the kinetics of substances under nanoscale\nconfinement.