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HERO ID
4969015
Reference Type
Journal Article
Title
Structure and friction of stearic acid and oleic acid films adsorbed on iron oxide surfaces in squalane
Author(s)
Doig, M; Warrens, CP; Camp, PJ
Year
2014
Is Peer Reviewed?
1
Journal
Langmuir
ISSN:
0743-7463
EISSN:
1520-5827
Volume
30
Issue
1
Page Numbers
186-195
Language
English
PMID
24364665
DOI
10.1021/la404024v
Web of Science Id
WOS:000330001600024
Abstract
The structure and friction of fatty acid surfactant films adsorbed on iron oxide surfaces lubricated by squalane are examined using large-scale molecular dynamics simulations. The structures of stearic acid and oleic acid films under static and shear conditions, and at various surface coverages, are described in detail, and the effects of unsaturation in the tail group are highlighted. At high surface coverage, the measured properties of stearic acid and oleic acid films are seen to be very similar. At low and intermediate surface coverages, the presence of a double bond, as in oleic acid, is seen to give rise to less penetration of lubricant in to the surfactant film and less layering of the lubricant near to the film. The kinetic friction coefficient is measured as a function of shear rate within the hydrodynamic (high shear rate) lubrication regime. Lubricant penetration and layering are observed to be correlated with friction coefficient. The friction coefficient with oleic acid depends only weakly on surface coverage, while stearic acid admits more lubricant penetration, and its friction coefficient increases significantly with decreasing surface coverage. Connections between film structure and friction are discussed.
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OPPT
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Squalane
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