Understanding the mechanism(s) by which inorganic additives reduce friction

Graph showing the binding energy and intensity

Molybdenum-sulfur additives such as Molybdenum Dialkyldithiocarbamates (MoDTCs) are molecular species in automotive lubricant formulations. The role of these additives is to break down under the sliding contacts within an automotive engine to form molybdenum disulfide (MoS2). MoS2 is a low-friction lattice material that reduces frictional energy waste in engines to improve fuel efficiency.

In recent years there have been increasingly stringent environmental restrictions placed upon automotive engine lubricants in terms of permissible sulfur levels. In order to meet these regulations, new molybdenum additive structures need to be developed with less sulfur than MoDTCs.

My work focusses upon relating the performance of molybdenum-sulfur additives to their chemical structures. With this, we aim to understand structure-activity relationships between molybdenum additives in order to reduce lubricant sulfur loadings. This is done through a mixture of tribological testing and surface analysis techniques such as XPS, XRD, TEM and Raman spectroscopy.