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Lubrication mechanism of a strong tribofilm by imidazolium ionic liquid

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Title: Lubrication mechanism of a strong tribofilm by imidazolium ionic liquid
Authors: Song, W
Zhang, J
Campen, S
Yan, J
Hongbing, J
Wong, J
Item Type: Journal Article
Abstract: Friction modifiers are surface-active additives added to base fluids to reduce friction between rubbing surfaces. Their effectiveness depends on their interactions with rubbing surfaces and may be mitigated by the choice of the base fluid. In this work, the performance of an imidazolium ionic liquid (ImIL) additive in polyethylene-glycol (PEG) and 1,4-butanediol for lubricating steel/steel and diamond-like-carbon/diamond-like carbon (DLC-DLC) contacts were investigated. ImIL containing PEG reduces friction more effectively in steel-steel than DLC-DLC contacts. In contrast, adding ImIL in 1,4-butanediol results in an increase in friction in steel-steel contacts. Results from Raman spectroscopy, XPS and FIB-TEM reveal that a surface film is formed on steel during rubbing in ImIL containing PEG. This film consists of two layers. The top layer is composed of amorphous carbon and are easily removed during rubbing. The bottom layer, which contains iron oxide and nitride compound, adheres strongly on the steel surface. This film maintains its effectiveness in a steel-steel contact even after ImIL additives are 2 depleted. Such film is not observed in 1,4-butanediol where the adsorption of ImIL is hindered, as suggested by QCM measurements. No benefit is observed when the base fluid on its own is sufficiently lubricious, as in the case of DLC surfaces. This work provides fundamental insights on how compatibilities among base fluid, friction modifier and rubbing surface affect performance of IL as surface active additives. It reveals the structure of an ionic liquid surface film, which is effective and durable. The knowledge is useful for guiding future IL additive development.
Issue Date: 1-Mar-2023
Date of Acceptance: 3-Mar-2022
URI: http://hdl.handle.net/10044/1/95966
DOI: 10.1007/s40544-022-0614-9
ISSN: 2223-7690
Publisher: SpringerOpen
Start Page: 425
End Page: 440
Journal / Book Title: Friction
Volume: 11
Copyright Statement: © The author(s) 2022. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/
Publication Status: Published
Online Publication Date: 2022-06-12
Appears in Collections:Mechanical Engineering
Faculty of Engineering

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