Effects of Temperature, Pressure and Shear on the Phases Formed by Lubricant Additives: A Sub-Microfocus X-ray Scattering Study of a Dynamic

Operando sub-microfocus XRD/PDF/SAXS studies will be performed to obtain information about the chemical composition of interfacial phases formed on steel by novel vanadium lubricant additives, under friction conditions in a tribological contact. Vanadium(IV) oxyacetylacetonates are a new class of lubricant additives that achieve a remarkable reduction of friction and wear in engines, with potential to replace conventional zinc dialkyl dithiophosphate (ZDDP) lubrication technology. From X-ray scattering in a bespoke environmental tribometer we will seek to identify interfacial phases formed by complex mechanochemistry, as a function of time and friction conditions. XRD, SAXS and XPDF will provide combined information about ordered, disordered and colloidal phases. Our study builds on X-ray photoelectron spectroscopy (XPS) studies, which indicate the presence of phases of three V oxidation states (III, IV and V) but do not identify the actual vanadium phases.