Structural effects in nanotribology of nanoscale films of ionic liquids confined between metallic surfaces
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Author(s)
Di Lecce, Silvia
Kornyshev, Alexei A
Urbakh, Michael
Bresme, Fernando
Type
Journal Article
Abstract
Room Temperature Ionic Liquids (RTILs) attract significant interest in nanotribology. However, their microscopic lubrication mechanism is still under debate. Here, using non-equilibrium molecular dynamics simulations, we investigate the lubrication performance of ultra-thin (<2 nm) films of [C2MIM]+ [NTf2]− confined between plane-parallel neutral surfaces of Au(111) or Au(100). We find that films consisting of tri-layers or bilayers, form ordered structures with a flat orientation of the imidazolium rings with respect to the gold surface plane. Tri-layers are unstable against loads >0.5 GPa, while bi-layers sustain pressures in the 1–2 GPa range. The compression of these films results in monolayers that can sustain loads of several GPa without significant loss in their lubrication performance. Surprisingly, in such ultra-thin films the imidazolium rings show higher orientational in-plane disorder, with and the rings adopting a tilted orientation with respect to the gold surface. The friction force and friction coefficient of the monolayers depends strongly on the structure of the gold plates, with the friction coefficient being four times higher for monolayers confined between Au(100) surfaces than for more compact Au(111) surfaces. We show that the general behaviour described here is independent of whether the metallic surfaces are modelled as polarizable or non-polarizable surfaces and speculate on the nature of this unexpected conclusion.
Date Issued
2021-09-17
Date Acceptance
2021-09-17
Citation
Physical Chemistry Chemical Physics, 2021, 23 (38), pp.22174-22183
ISSN
1463-9076
Publisher
Royal Society of Chemistry
Start Page
22174
End Page
22183
Journal / Book Title
Physical Chemistry Chemical Physics
Volume
23
Issue
38
Copyright Statement
© the Owner Societies 2021. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.
Identifier
http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000700552500001&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=1ba7043ffcc86c417c072aa74d649202
Subjects
Science & Technology
Physical Sciences
Chemistry, Physical
Physics, Atomic, Molecular & Chemical
Chemistry
Physics
FRICTION
SUPERLUBRICITY
LUBRICATION
SIMULATIONS
TRANSITION
MONOLAYER
LUBRICITY
MODEL
Publication Status
Published
Date Publish Online
2021-09-17