2024/08/29 by Hongyu Gao, Gao, Hongyu, Sergey Sukhomlinov +1
Environmental Science · Engineering · #Recycling and Waste Management Techniques #Fiber-reinforced polymer composites
paper · pdf · doi:10.48550/arxiv.2408.16677
Structural lubricity arises typically at incommensurate, well-defined dry contacts where short-range elastic instability is significantly mitigated. However, under ambient conditions, airborne molecules adsorb onto solid surfaces, forming an intervening viscous medium that alters interfacial properties. Using molecular dynamics simulations with a newly parameterized interfacial potential, we investigate the preservation of ultralow friction on graphite with physisorbed n-hexadecane (HEX) as a model contaminant. Our findings reveal that a well-ordered monolayer of HEX molecules strongly adheres to the graphite surface, replicating its lattice structure and maintaining solid-like behavior, which leads to orientation-dependent shear stresses-an effect absent on a gold (111) surface. As the contaminant film thickens, this orientation effect diminishes. Additionally, as coverage increases from zero to one monolayer, the shear stress-velocity relationship transitions from Coulomb to quasi-Stokesian and then to quasi-Coulomb, highlighting the role of molecular displacement in high-velocity dissipation. Despite a hundredfold increase in shear stress compared to dry sliding, superlubricity on graphite persists under ambient conditions, enhancing our conventional understanding of structural lubricity.