Role of interfacial water in adhesion, friction, and wear—A critical review

Abstract

Surficial water adsorption and interfacial water condensation as natural phenomena that can alter the contact status of the solid interface and tribological performances are crucial in all length scales, i.e., from earthquakes to skating at the macroscale level and even to micro/nano-electromechanical systems (M/NEMS) at the microscale/nanoscale level. Interfacial water exhibits diverse structure and properties from bulk water because of its further interaction with solid surfaces. In this paper, the evolutions of the molecular configuration of the adsorbed water layer depending on solid surface chemistry (wettability) and structure, environmental conditions (i.e., relative humidity and temperature), and experimental parameters (i.e., sliding speed and normal load) and their impacts on tribological performances, such as adhesion, friction, and wear, are systematically reviewed. Based on these factors, interfacial water can increase or reduce adhesion and friction as well as facilitate or suppress the tribochemical wear depending on the water condensation kinetics at the interface as well as the thickness and structure of the involved interfacial water.

In Situ Atomic-Scale Imaging of Interfacial Water under 3D Nanoscale Confinement

“…Capillary condensation of water from vapor is a common phenomenon that happens in the gap between two neighboring solid surfaces under some thermodynamic conditions. It has many implications in different fields such as tribology, 1 adhesion, 2 nanolithography, 3 and fuel recovery. 4 Despite its ubiquitous nature, some relevant features of capillary condensation are poorly understood.…”

“…Initially, experiments were performed in liquid water confined between two large mica surfaces (surface force apparatus). 12 , 14 , 15 Later, AFM setups were implemented to measure the adhesion force of nanoscale water bridges 1 , 16 or to study solid–water interfaces. 17 Recently, water trapped between a solid surface and a large 2D materials surface (graphene or hexagonal BN) was used to study the properties of confined water.…”

Indigo—A New Tribological Substance Class for Non-Toxic and Ecological Gliding Surfaces on Ice, Snow, and Water

“…It has often been hypothesized that in skating or skiing, the surfaces are lubricated by a layer of water formed by pressure melting [ 61 ], as proven by experiments [ 62 ]. Above approximately −16 °C, a tribo-water film is formed by friction on ice and snow [ 63 , 64 , 65 ], upon which winter sports equipment, such as skates, sleds, skis, or snowboards, glide. Below this temperature, wet friction changes to dry friction, with higher coefficients of friction.…”

Origin of friction hysteresis on monolayer graphene

“…When the tip slides against the graphite surface, the topmost graphene layer delaminates from the graphite, which results in a significant increase in friction as the applied normal load is decreased (negative friction coefficient). Additionally, airborne hydrocarbons and other small molecules inevitably adsorb on the surfaces of 2D materials when exposed to ambient air, which could affect their surface properties [20][21][22][23][24][25]. It has been demonstrated that airborne contaminants can cause the hydrophilic surface of 2D materials to become hydrophobic [21,24].…”