The Effects of Humidity on the Velocity-Dependence and Frictional Ageing of Nanoscale Silica Contacts

作者：J. Brandon McClimon, Zhuohan Li, Khagendra Baral, D. L. Goldsby, Izabela Szlufarska, Robert W. Carpick · 发表于：Tribology Letters · 年份：2024 · DOI：10.1007/s11249-024-01904-x · 被引用次数：7 · 研究领域：Force Microscopy Techniques and Applications、Tunneling and Rock Mechanics、Adhesion, Friction, and Surface Interactions

Abstract This work examines the effect of environmental humidity on rate-and-state friction behavior of nanoscale silica-silica nanoscale contacts in an atomic force microscope, particularly, its effect on frictional ageing and velocity-weakening vs. strengthening friction from 10 nm/s to 100 μm/s sliding velocities. At extremely low humidities ( $$\ll 1\% RH$$ ≪ 1 % R H ), ageing is nearly absent for up to 100 s of nominally stationary contact, and friction is strongly velocity-strengthening. This is consistent with dry interfacial friction, where thermal excitations help overcome static friction at low sliding velocities. At higher humidity levels (10–40% RH), ageing becomes pronounced and is accompanied by much higher kinetic friction and velocity-weakening behavior. This is attributed to water-catalyzed interfacial Si–O-Si bond formation. At the highest humidities examined (> 40% RH), ageing subsides, kinetic friction drops to low levels, and friction is velocity-strengthening again. These responses are attributed to intercalated water separating the interfaces, which precludes interfacial bonding. The trends in velocity-dependent friction are reproduced and explained using a computational multi-bond model. Our model explicitly simulates bond formation and bond-breaking, and the passivation and reactivation of reaction sites across the interface during sliding, where the activation energies for interfacial chemical reactions are dependent on humidity....