The Effects of Temperature, Pressure and Shear on the Oxidation States and Local Structure of Oil Lubricant Additives: A V K-edge Operando X

Operando V K-edge XAS studies will be performed to obtain chemical composition information about the interfacial phases formed on steel by novel vanadium (V) lubricant additives, under friction conditions in a tribological contact. V(IV) oxyacetylacetonates are a new class of additives that achieve a remarkable reduction of friction and wear in engines, with potential to replace zinc dialkyl dithiophosphates (ZDDPs). The chemical composition of the V phases, which are likely formed by complex mechanochemistry in the tribological contact, will be followed as a function of time and friction conditions in a bespoke tribometer. Combined FY and TEY XAS will be used to build on ex situ XPS studies, which indicate the presence of V(III), V(IV) and V(V) but do not identify the chemical nature of the phases. The molecular-level mechanistic information obtained will enable the development of more effective and sustainable anti-wear additives.