Cited by 81Lubricants and Their AdditivesForce Microscopy Techniques and ApplicationsTribology and Lubrication Engineering

Ionic Liquid Lubrication of Stainless Steel: Friction is Inversely Correlated with Interfacial Liquid Nanostructure

Cooper, Peter K., Wear, Callan J., Li, Hua, Atkin, Rob·2017·ACS Sustainable Chemistry & Engineering

Abstract

Atomic force microscopy (AFM) is used to measure the friction of a stainless steel surface lubricated with six different ionic liquids (ILs). The measurements reveal that, contrary to expectations, friction and the degree of interfacial ionic liquid nanostructure are inversely correlated. Six ILs were confined between a sharp Si tip and a stainless steel surface, and the friction force was measured as a function of normal load. Trihexyl(tetradecyl)phosphonium bis(trifluoromethane)sulfonamide (P 6,6,6,14 TFSI) and trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl)phosphinate (P 6,6,6,14 ( i C 8 ) 2 PO 2 ) are the most effective lubricants, reducing lateral forces and friction coefficients by up to 3 times compared with the imidazolium-based ILs and the shorter-chained P 4,4,4,1 TFSI. Force–separation profiles reveal no obvious interfacial layers for P 6,6,6,14 ( i C 8 ) 2 PO 2 and P 6,6,6,14 TFSI, in contrast to extensive layering for the other ILs. The bulkiness of the [P 6,6,6,14 ] + cation weakens the electrostatic interaction with the anion, resulting in weaker structure near the surface. The sliding AFM tip expels the weak near surface structure with minimal energy loss (low friction), whereas for the strongly structured ILs, more energy is dissipated by breaking the stronger interlayer bonds. The inverse correlation between friction and IL structure can be used to design weakly structured ILs which are excellent lubricants.

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Crossref · 10.1021/acssuschemeng.7b03262

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Authors
Cooper, P. K., Wear, C. J., Li, H., & Atkin, R.
Affiliations
  • The University of Western Australia (AU)
  • University of Newcastle Australia (AU)
Corresponding author
Atkin, Rob
Venue
ACS Sustainable Chemistry & Engineering
Published
2017-11-01
Volume
5
Issue
12
Pages
11737-11743
ISSN
2168-0485 (ISSN-L)
OpenAlex
W2766249172
Cited by
81
References
61
Citations by year
2026: 3 · 2025: 8 · 2024: 15 · 2023: 6 · 2022: 12 · 2021: 8 · 2020: 10 · 2019: 10 · 2018: 9
FWCI
6.16
Type
journal article
Language
en
Open access
closed
Locations
  • ACS Sustainable Chemistry & Engineering (publishedVersion)
  • UWA Profiles and Research Repository (UWA) (submittedVersion)
Funders
  • University of Western Australia
  • Australian Research Council
  • Australian Institute of Nuclear Science and Engineering
Topics
  • Physical Sciences › Engineering › Mechanical Engineering › Lubricants and Their Additives
  • Physical Sciences › Physics and Astronomy › Atomic and Molecular Physics, and Optics › Force Microscopy Techniques and Applications
  • Physical Sciences › Engineering › Mechanical Engineering › Tribology and Lubrication Engineering
Keywords
ionic liquids, stainless steel, friction, interfacial nanostructure, imidazolium ionic liquids, friction coefficient, interlayer bonding, lubricant design

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