TY - JOUR
T1 - Diamond-like carbon coating under oleic acid lubrication
T2 - Evidence for graphene oxide formation in superlow friction
AU - De Barros Bouchet, Maria Isabel
AU - Martin, Jean Michel
AU - Avila, José
AU - Kano, Makoto
AU - Yoshida, Kentaro
AU - Tsuruda, Takeshi
AU - Bai, Shandan
AU - Higuchi, Yuji
AU - Ozawa, Nobuki
AU - Kubo, Momoji
AU - Asensio, Maria C.
N1 - Funding Information:
The authors gratefully acknowledge Mr. Fabio Demarco for scientific discussions. We also acknowledge the valuable help of Stephane Lorcy and the technical serviced of the Synchrotron Soleil, which is supported by the Centre National de la Recherche Scientifique (CNRS).
Publisher Copyright:
© The Author(s) 2017.
PY - 2017/4/12
Y1 - 2017/4/12
N2 - 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.
AB - 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.
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U2 - 10.1038/srep46394
DO - 10.1038/srep46394
M3 - Article
C2 - 28401962
AN - SCOPUS:85017419084
SN - 2045-2322
VL - 7
JO - Scientific Reports
JF - Scientific Reports
M1 - 46394
ER -