Diamond-like carbon coating under oleic acid lubrication: Evidence for graphene oxide formation in superlow friction

Maria Isabel De Barros Bouchet, Jean Michel Martin, José Avila, Makoto Kano, Kentaro Yoshida, Takeshi Tsuruda, Shandan Bai, Yuji Higuchi, Nobuki Ozawa, Momoji Kubo, Maria C. Asensio

Research output: Contribution to journalArticlepeer-review

41 Citations (Scopus)

Abstract

The achievement of the superlubricity regime, with a friction coefficient below 0.01, is the Holy Grail of many tribological applications, with the potential to have a remarkable impact on economic and environmental issues. Based on a combined high-resolution photoemission and soft X-ray absorption study, we report that superlubricity can be realized for engineering applications in bearing steel coated with ultra-smooth tetrahedral amorphous carbon (ta-C) under oleic acid lubrication. The results show that tribochemical reactions promoted by the oil lubrication generate strong structural changes in the carbon hybridization of the ta-C hydrogen-free carbon, with initially high sp 3 content. Interestingly, the macroscopic superlow friction regime of moving mechanical assemblies coated with ta-C can be attributed to a few partially oxidized graphene-like sheets, with a thickness of not more than 1 nm, formed at the surface inside the wear scar. The sp2 planar carbon and oxygen-derived species are the hallmark of these mesoscopic surface structures created on top of colliding asperities as a result of the tribochemical reactions induced by the oleic acid lubrication. Atomistic simulations elucidate the tribo-formation of such graphene-like structures, providing the link between the overall atomistic mechanism and the macroscopic experimental observations of green superlubricity in the investigated ta-C/oleic acid tribological systems.

Original languageEnglish
Article number46394
JournalScientific reports
Volume7
DOIs
Publication statusPublished - 2017 Apr 12

ASJC Scopus subject areas

  • General

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