Iron-Nanoparticle Driven Tribochemistry Leading to Superlubric Sliding Interfaces

D Berman and KC Mutyala and S Srinivasan and SKRS Sankaranarayanan and A Erdemir and EV Shevchenko and AV Sumant, ADVANCED MATERIALS INTERFACES, 6, 1901416 (2019).

DOI: 10.1002/admi.201901416

Any moving mechanical system consisting of sliding/rolling or rotating interfaces experiences friction and wear. High contact pressure and shear during relative movement of the sliding interfaces in the presence of lubricants often lead to interesting tribochemical activity at nanoscale, which then greatly influences the tribological performance of the mechanical systems at macroscale. Understanding these tribochemical interactions and to be able to manipulate them will be a key in designing smart solid lubricants that can self-generate at the sliding interfaces and thus help in drastically improving the overall efficiency of these moving mechanical systems. In this study, it is demonstrated that solid lubricant consisting graphene mixed with iron nanoparticles (NPs) under high contact pressures at the sliding interface undergo tribochemical reaction leading to the formation of onion-like-carbon nanostructures (OLCs). Combining with atomistic molecular dynamic simulations, the tribochemical mechanism of formation of OLC with pure iron NPs and how that depends sensitively on the core-shell chemistry of the nanoparticle is elucidated. Interestingly, the formed OLCs lead to the near-zero friction (superlubricity) during sliding in dry conditions, thus demonstrating great potential to be used as a solid lubricant for various tribological applications.

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