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Open AccessArticle

Influence of Water on Tribolayer Growth When Lubricating Steel with a Fluorinated Phosphonium Dicyanamide Ionic Liquid

1
Department of Chemical and Geological Sciences, University of Cagliari, Campus of Monserrato (CA), I09042 Monserrato, Italy
2
Laboratory for Surface Science and Technology, Department of Materials, ETH Zurich, Vladimir-Prelog-Weg 5, CH-8093 Zürich, Switzerland
3
INM—Leibniz Institute for New Materials, Campus D2 2, 66123 Saarbrücken, Germany
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Transfer Center Sustainable Electrochemistry, Saarland University and KIST Europe, Am Markt, Zeile 3, 66125 Saarbrücken, Germany
5
Colloid and Interface Chemistry, Saarland University, Campus D2 2, 66123 Saarbrücken, Germany
*
Authors to whom correspondence should be addressed.
Current address: School of Materials Science and Engineering, Key Laboratory for Polymeric Composite and Functional Materials of Ministry of Education, Sun Yat-sen University, Guangzhou 510275, China.
Lubricants 2019, 7(3), 27; https://doi.org/10.3390/lubricants7030027
Received: 4 March 2019 / Revised: 18 March 2019 / Accepted: 19 March 2019 / Published: 22 March 2019
(This article belongs to the Special Issue Ionic Liquids: Friction and Lubrication Mechanisms)
This work aims to elucidate the role of environmental humidity on the tribological behavior of steel surfaces lubricated with an ionic liquid comprised of a fluorinated phosphonium cation—tributyl-3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluoro-octyl-phosphonium—and a dicyanamide anion (i.e. N(CN)2). Ball-on-disk tribotests were carried out at room temperature and at various levels of relative humidity (RH). Water was found to be required to promote the formation of a tribofilm over the contact area. The reaction layer exhibited a patchy morphology, which resembles that observed formed with conventional antiwear additives such as ZnDTP. A surface-chemical analysis of the tribofilm indicated that the tribofilm is composed of fluorides, oxides, and phosphates, pointing to a stress-induced degradation of the ions and corrosion of the sliding counterparts, which is enabled by the presence of water at the sliding interface. View Full-Text
Keywords: Ionic liquids; tribofilm; mechanochemistry; lubrication; small-area X-ray photoelectron spectroscopy Ionic liquids; tribofilm; mechanochemistry; lubrication; small-area X-ray photoelectron spectroscopy
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MDPI and ACS Style

Urtis, L.A.; Arcifa, A.; Zhang, P.; Du, J.; Fantauzzi, M.; Rauber, D.; Hempelmann, R.; Kraus, T.; Rossi, A.; Spencer, N.D. Influence of Water on Tribolayer Growth When Lubricating Steel with a Fluorinated Phosphonium Dicyanamide Ionic Liquid. Lubricants 2019, 7, 27.

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