Manipulating friction with 2D materials-nanoparticles ensembles

A. Sumant
Argonne National Laboratory,
United States

Keywords: 2D materials, graphene


Mechanical/tribological subsystems are an integral part of any moving transportation system. Minimizing friction and wear-related mechanical failures remains as one of the greatest challenges in today’s moving mechanical systems. In my talk, I will describe a process that we have developed by using a combination of 2D materials with nanodiamonds to manipulate friction at nanoscale and how collectively it affects friction and wear at macroscale. We show an interesting observation of generating a solid lubricant in-situ at the tribological interface during sliding leading to superlubricity at macroscale in dry environment. We demonstrate that two dimensional (2D) layered materials such as molybdenum disulfide (MoS2) is capable of demonstrating superlubricity through unique tribocatalytic reaction with carbon leading to in-situ formation of onion-like carbon (OLC) directly at the tribological contact in dry nitrogen environment. We have observed that beyond some initial run-in period, the friction comes down to superlubric regime (0.005) and maintains in that state for a very long period of time, despite the fact that introduced 2D flakes of MoS2 are only a few nanometer thick. Our initial experimental and theoretical investigations suggest that formation of OLCs is possible through tribocatalytic reaction with these 2D materials that could occur at the sliding interface due to the high contact pressure. These OLCs behaves in a similar way described earlier in our previous studies [1], providing reduced contact area and incommensurability with respect to the sliding DLC surface leading to superlubricity. I will discuss the possible mechanism and highlight the similarities and differences with the previously demonstrated superlubricity involving graphene-nanodamond ensembles [1]. This new discovery broadens the fundamental understanding of frictional behavior of 2D materials beyond graphene and opens a wide range of possibilities for implementing them in mechanical and tribological applications involving static, sliding, and rotating contacts. References: 1. Berman, Deshmukh, Sankaranarayanan, Erdemir, and Sumant, Science, 348, 6239, 1118 (2015)