Koshigan, KD, Mangolini, F, McClimon, JB et al. (4 more authors) (2015) Understanding the hydrogen and oxygen gas pressure dependence of the tribological properties of silicon oxide-doped hydrogenated amorphous carbon coatings. Carbon, 93. 851 - 860. ISSN 0008-6223
Abstract
Silicon oxide-doped hydrogenated amorphous carbons (a–C:H:Si:O) are amorphous thin films used as solid lubricants in a range of commercial applications, thanks to its increased stability in extreme environments, relative to amorphous hydrogenated carbons (a–C:H). This work aims to develop a fundamental understanding of the environmental impact on the tribology of a–C:H:Si:O. Upon sliding an a–C:H:Si:O film against a steel counterbody, two friction regimes develop: high friction in high vacuum and low gas pressure (oxygen pressure < 10 mbar; hydrogen pressure < 50 mbar), and a low friction regime at higher gas pressures (10 mbar < oxygen pressure < 500 mbar; 50 mbar < hydrogen pressure < 1000 mbar). Scanning electron microscopy (SEM) revealed that the tribological behavior of a–C:H:Si:O is governed by adhesive junctions at the sliding interface. At low gas pressures, material transfer from the steel pin to the a–C:H:Si:O flat occurs. At higher gas pressures, a tribofilm forms on the steel countersurface. Raman and near edge X-ray absorption spectroscopy (NEXAFS) spectroscopies demonstrate that upon sliding under the higher gas pressure, low friction regime, a surface layer with an elevated fraction of sp2-bonded carbon atoms forms. These changes indicate that these gases favor the release of the adhesive junctions by dissociatively reacting with the mechanically-stressed sp2 carbon-rich surface layer.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2015 Elsevier Ltd. All rights reserved. This is an author produced version of a paper published in Carbon. Uploaded in accordance with the publisher's self-archiving policy. |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Mechanical Engineering (Leeds) > Institute of Functional Surfaces (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 17 Nov 2015 14:51 |
Last Modified: | 12 Jun 2016 20:09 |
Published Version: | http://dx.doi.org/10.1016/j.carbon.2015.06.004 |
Status: | Published |
Publisher: | Elsevier |
Identification Number: | 10.1016/j.carbon.2015.06.004 |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:91772 |