Electrotunable friction in diluted room temperature ionic liquids: implications for nanotribology
File(s)
Author(s)
Pivnic, K
Bresme, F
Kornyshev, AA
Urbakh, M
Type
Journal Article
Abstract
Using nonequilibrium molecular dynamics (NEMD) simulations, we study the mechanism of electrotunable friction in the mixture of a room temperature ionic liquid (RTIL), BMIM PF6, and an organic solvent, acetonitrile. The dilution itself helps to reduce the viscosity and thereby reduce the viscous contribution to friction. At the same time, we find that under nanoscale confinement conditions, diluted RTIL solutions, of just ∼10% molar fraction, still feature a remarkable variation of the friction force with the electrode surface charge density, not weaker than had been earlier shown for nanoconfined pure RTILs. In both classes of systems the electrotunable friction response is due to accumulation of counterions at charged surfaces. For both diluted mixtures and pure RTILs, the friction force is minimal for uncharged surfaces and it increases with surface charge of either sign but only in the range of low and moderate surface charges (16–32 μC/cm2). At higher surface charges (43–55 μC/cm2), the effect is different: in the pure RTIL, the friction force continues to increase with the surface charge, while in the diluted RTIL mixture it features a maximum, with a reduction of friction with the increasing surface charge. This contrasting behavior is explained by the difference in the slip conditions found for the pure and the diluted RTIL solutions in contact with highly charged surfaces. Overall, we demonstrate that nanoscale films of diluted mixtures of RTIL provide lower friction forces than the pure RTIL films, preserving at the same time a significant electrotunable response when the liquids are confined between symmetrically charged surfaces. Nanoconfinement between asymmetrically charged surfaces leads to a reduction of friction compared to the symmetric case, with a concomitant decrease in the range of friction variation with the surface charge density. Our results highlight the potential of diluted RTIL mixtures as cost-effective electrotunable lubricants for future nanotribological applications.
Date Issued
2020-11-25
Date Acceptance
2020-10-05
ISSN
2574-0970
Publisher
American Chemical Society
Start Page
10708
End Page
10719
Journal / Book Title
ACS Applied Nano Material
Volume
3
Issue
11
Copyright Statement
© 2020 American Chemical Society. This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Applied Nano Material, after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acsanm.0c01946
Sponsor
The Leverhulme Trust
Identifier
https://pubs.acs.org/doi/10.1021/acsanm.0c01946
http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000595546500018&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=1ba7043ffcc86c417c072aa74d649202
Grant Number
RPG-2016-223
Subjects
Science & Technology
Technology
Nanoscience & Nanotechnology
Materials Science, Multidisciplinary
Science & Technology - Other Topics
Materials Science
nanotribology
electrotunable friction
ionic liquids
organic solvents
molecular dynamics simulations
interfacial slippage
Science & Technology
Technology
Nanoscience & Nanotechnology
Materials Science, Multidisciplinary
Science & Technology - Other Topics
Materials Science
nanotribology
electrotunable friction
ionic liquids
organic solvents
molecular dynamics simulations
interfacial slippage
Publication Status
Published
Date Publish Online
2020-10-15