Effect of surface hydrophilicity and water vapor pressure on the interfacial shear strength of adsorbed water layer

Abstract

We investigated the effect of water vapor pressure and surface hydrophilicity on the tribological behavior in wearless sliding condition. Friction and interfacial shear strength of silicon surfaces with different water affinity (contact angles of <5degrees, 30degrees, and 85degrees) against a glass sphere (contact angle 40degrees) were examined under various water vapor pressure conditions. The friction of hydrophilic surface decreased as vapor pressure increased and the least hydrophilic surface showed stable and low friction force regardless of relative vapor pressure. However, it showed that the hydrophilic surface with high relative vapor pressure exhibited lower shear strength than a less hydrophilic surface independent of capillary effect. It was explained in terms of capillary wetting and the role of adsorbed water in contact area. (C) 2004 American Institute of Physics.