Friction and slip behaviors of confined glycerol on rough surface: Effect of temperature, pressure, and sliding velocity

Understanding nanoscale lubrication mechanisms is critical for minimizing frictional energy dissipation. This study investigates the tribological response of nanoconfined glycerol lubricating film between a polar SiO₂ slab and a non-polar stepped CH-terminated asperity using molecular dynamics simulations. We reveal that friction and wall slip are governed by the dynamic evolution of the glycerol H-bond network under varying temperatures (300–450 K), pressures (250–1000 MPa), and sliding velocities (10–100 m/s). Elevated temperatures disrupt these H-bonds and significantly reduce viscosity, transitioning the system into a low-slip state with decreased friction. Conversely, high pressure densifies the film and strengthens the H-bond network, sustaining wall slip and excellent anti-friction performance. Although high sliding velocities induce shear heating, the resulting drop in viscosity offsets the increased shear rate, maintaining both a steady friction coefficient and wall slip. These findings provide atomic-level insights into how coupled thermal, mechanical, and kinetic factors govern boundary lubrication, offering theoretical guidance for the design of high-performance nano-lubricants for heterogeneous interfaces.