Tribological properties of alkyl and hydroxyl groups on the imidazolium tetrafluoroborate ionic liquids

We present an investigation of effect of alkyl chain length and hydroxyl group functionalisation on the tribological properties of imidazolium tetrafluoroborate ionic liquids. Four kinds of hydroxyl-functionalised ionic liquids with the alkyl chain of C-1-C-10 were synthesised, and the relationships between their structure and physicochemical properties such as viscosity, thermal stability and corrosion, before and after incorporation of a hydroxyl group, were measured. In particular, the studies on their lubrication properties as ionic liquid (IL) lubricants for steel-steel contacts, including the friction coefficient, the wear volume and so on, were particularly emphasised. Moreover, an in-depth exploration about the function mechanism and failure mode of the ILs during the friction process were studied using the scanning electron microscope and X-ray photoelectron spectroscope technologies, and a proposed interaction model between ILs and steel substrate was presented. Copyright (c) 2012 John Wiley & Sons, Ltd.