Behaviour of n-alkanes confined between iron oxide surfaces at high pressure and shear rate: A nonequilibrium molecular dynamics study

The behaviour of n-alkanes confined and sheared between iron oxide surfaces has been studied using nonequilibrium molecular dynamics simulations. The molecular extension, orientation, film structure, flow, and friction have been investigated for a range of n-alkane chain lengths under conditions rep...

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Bibliographic Details
Published in:Tribology international 2019-09, Vol.137, p.420-432
Main Authors: Echeverri Restrepo, Sebastián, van Eijk, Marcel C.P., Ewen, James P.
Format: Article
Language:English
Subjects:
Alkanes
Coefficient of friction
Couette flow
Dynamic structural analysis
Elastohydrodynamic lubrication
Iron oxides
Long range order
Lubrication
Molecular dynamics
Molecular structure
Shear rate
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Summary:The behaviour of n-alkanes confined and sheared between iron oxide surfaces has been studied using nonequilibrium molecular dynamics simulations. The molecular extension, orientation, film structure, flow, and friction have been investigated for a range of n-alkane chain lengths under conditions representative of the elastohydrodynamic lubrication regime. At high pressure, the molecules show strong layering and long-range order, suggesting solid-like films. Conversely, high shear rates result in less elongated, layered, and ordered molecules; indicating more liquid-like films. Although Couette flow is usually observed for short n-alkanes, the flow is often non-linear for long n-alkanes. The friction coefficient increases logarithmically with shear rate, but the slope decreases with increasing pressure such that it becomes insensitive to shear rate for long n-alkanes.
ISSN:0301-679X
1879-2464
DOI:10.1016/j.triboint.2019.05.008