Carlos Ayestaran Latorre
Project title: Unravelling the role of mechanochemistry in lubrication mechanisms
Supervisors: Prof. Daniele Dini, Prof. Hugh A. Spikes, Dr James P Ewen
The Tribology Group at Imperial College London has recently shown conclusively that the applied shear stress and thus mechanochemistry controls the reaction of the most widely applied antiwear additive, zinc dialkylthiphosphate (ZDDP).
The core aims of the project are to improve the understanding of the extent to which mechanochemistry drives the film formation of antiwear additives and the influence of ZDDP structure on antiwear film formation to develop quantitative rules for ZDDP design. We will also compare the film formation and wear reduction performance of proprietary acid phosphate additives designed by Afton to conventional ZDDPs.
Classical nonequilibrium molecular dynamics (NEMD) simulations of ZDDP solvated in simple lubricants and will be performed. Variations in tensile forces and bond lengths within the additive molecules will give an indication as to the likelihood of breakdown of the additives molecules which precedes the formation of tribofilms.
However, in order to directly study mechanochemical processes, one must explicitly model chemical reactivity under shear conditions. We propose a combination of both classical NEMD simulations, using reactive potentials which allow bond-breaking, and ab initio MD techniques, to validate the results obtained by these force-fields.