Controlled microtribology of a metal oxide surface

The rational control of the friction and wear (damage) of engineering, as opposed to model, surfaces under practical conditions such as high contact pressures has long been a technological challenge with much fundamental interest. Lubricant fluids and physisorbed surfactant monolayers (boundary lubricants) are effective friction modifiers but often fail at high loads. We show that the chemisorption of a suitably designed single-chained phosphonate surfactant onto crystalline α-alumina surfaces produces robust protective monolayers that significantly reduce the friction forces and wear even at high loads. The mechanisms are explained, which point to some general principles that offer a basis for scale-up in many different engineering systems.