Ionic liquid lubrication at electrified interfaces

Kong, Lingling; Wang, Xiaolei

doi:10.1088/0022-3727/49/22/225301

Cited by 29 publications

(22 citation statements)

References 21 publications

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“…8,9 Previous tribotronic IL studies have also reported that differences in cation alkyl chain lengths strongly affect their frictional properties and electric response. 10,11 In addition, when the length of the alkyl chain of the cation becomes significant, other effects can be driven. Previous measurements using the surface force apparatus (SFA) by Perkin et al have shown a transition from a monolayer to bilayer structure in [C 4 C 1 Im][NTf 2 ] and [C 6 C 1 Im][NTf 2 ] imidazoliumbased fluorinated ILs, respectively, when they are confined between two negatively charged mica surfaces.…”

Section: Introductionmentioning

confidence: 99%

Interfacial structuring of non-halogenated imidazolium ionic liquids at charged surfaces: effect of alkyl chain length

Watanabe

Pilkington

Oleshkevych

et al. 2020

Phys. Chem. Chem. Phys.

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Control of the interfacial structures of ionic liquids (ILs) at charged interfaces is important to many of their applications, including in energy storage solutions, sensors and advanced lubrication technologies utilising electric fields. In the case of the latter, there is an increasing demand for the study of nonhalogenated ILs, as many fluorinated anions have been found to produce corrosive and toxic halides under tribological conditions. Here, the interfacial structuring of a series of four imidazolium ILs ([C n C 1 Im]) of varying alkyl chain lengths (n = 5, 6, 7, 10), with a non-halogenated borate-based anion ([BOB]), have been studied at charged interfaces using sum frequency generation (SFG) spectroscopy and neutron reflectivity (NR). For all alkyl chain lengths, the SFG spectra show that the cation imidazolium ring responds to the surface charge by modifying its orientation with respect to the surface normal. In addition, the combination of SFG spectra with electrochemical NR measurements reveals that the longest alkyl chain length (n = 10) forms a bilayer structure at all charged interfaces, independent of the ring orientation. These results demonstrate the tunability of IL interfacial layers through the use of surface charge, as well as effect of the cation alkyl chain length, and provide valuable insight into the charge compensation mechanisms of ILs.

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Section: Introductionmentioning

confidence: 99%

Interfacial structuring of non-halogenated imidazolium ionic liquids at charged surfaces: effect of alkyl chain length

Watanabe

Pilkington

Oleshkevych

et al. 2020

Phys. Chem. Chem. Phys.

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“…The results obtained from the [BMIM]PF 6 measurements eliminated the influence of temperature as a dominant factor in adjusting lubricant performance. Therefore, the orientation and cumulating of the ionic liquid alkyl chains and layers [33,34] could be responsible for the phenomenon of electricity-induced external control of the smart lubricant rheology and lubricating layer behavior ( Fig. 8(a)).…”

Section: Friction Testsmentioning

confidence: 99%

Investigation of the tribological performance of ionic liquids in non-conformal EHL contacts under electric field activation

et al. 2020

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Real-time external alteration of the internal properties of lubricants is highly desirable in all mechanical systems. However, fabricating a suitable and effective smart lubricant is a long-lasting experimental process. In this study, the film thickness and frictional response of ionic liquid-lubricated non-conformal contacts to an electric field excitation under elastohydrodynamic conditions were examined. Film thickness was evaluated using a "ball-on-disc" optical tribometer with an electric circuit. Friction tests were carried on a mini traction machine (MTM) tribometer with a "ball-on-disc" rotation module and an electric circuit for contact area excitation. The results demonstrate that there is a difference in the behaviour of the ionic liquid during electric field excitation at the evaluated film thicknesses. The results of evaluated film thicknesses demonstrate that there is a difference in the behaviour of the ionic liquid during electric field excitation. Therefore, the ionic liquids could be a new basis for the smart lubrication of mechanical components. Moreover, the proposed experimental approach can be used to identify electrosensitive fluids. Friction 8(5): 982-994 (2020) 983 |www.Springer.com/journal/40544 | Friction http://friction.tsinghuajournals.comFriction 8(5): 982-994 (2020) | https://mc03.manuscriptcentral.com/frictionFriction 8(5): 982-994 (2020)

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“…[30][31][32][33][34][35][36] The nanometric solvation layers formed at the interface show resistance to normal compression and viscosity 1-3 order of magnitude higher than in the bulk liquid, the ions still maintaining a good degree of mobility. 16 The electrical and structural properties of the first few monolayers of IL in contact with the solid substrate can be crucial for the performance of devices employing ILs as electrolytes (as in supercapacitors, [4][5][6] solar cells [7][8][9][10] and batteries [11][12][13][14], gating media at electrified interfaces, [37][38][39] or active fluids (as for electrowetting [40][41][42][43] and tribology [44][45][46] ). The study of nanometer-sized IL systems (very thin films and nanostructures) on solid surfaces represents therefore a very interesting topic, since this configuration is relevant not only to address the effects of extreme spatial confinement of ILs, but it is also paradigmatic of the use of ILs in advanced applications.…”

Section: Introductionmentioning

confidence: 99%

“…to reduce wear), it could negatively affect the lubrication in macro, micro and nano-devices. 16,30,46,64 nanostructures assembled at room temperature on a variety of solid insulating substrates influence the electric properties of the IL layers, by means of a combined morphological and electrical analysis by AFM. We have shown that a conductive to insulating transition accompanies the surface-induced liquid to solid-like structural transition of solid-supported ILs, with a marked reduction of the dielectric constant compared to the bulk phase.…”

Section: Introductionmentioning

confidence: 99%

Surface confinement induces the formation of solid-like insulating ionic liquid nanostructures

Bovio¹,

Milani²,

Podestà

2017

Preprint

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We report on the modification of the electric properties of the imidazolium-based [BMIM][NTf2] ionic liquid upon surface confinement in the sub-monolayer regime. Solid-like insulating nanostructures of [BMIM][NTf2] spontaneously form on a variety of insulating substrates, at odd with the liquid and conductive nature of the same substances in the bulk phase. A systematic spatially resolved investigation by atomic force microscopy of the morphological, mechanical and electrical properties of [BMIM][NTf2] nanostructures showed that this liquid substance rearranges into lamellar nanostructures with a high degree of vertical order and enhanced resistance to mechanical compressive stresses and very intense electric fields, denoting a solid-like character. The morphological and structural reorganization has a profound impact on the electric properties of supported [BMIM][NTf2] islands, which behave like insulator layers with a relative dielectric constant between 3 and 5, comparable to those of conventional ionic solids, and significantly smaller than those measured in the bulk ionic liquid. These results suggest that in the solid-like ordered domains confined either at surfaces or inside the pores of the nanoporous electrodes of photo-electrochemical devices, the ionic mobility and the overall electrical properties can be significantly perturbed with respect to the bulk liquid phase, which would likely influence the<br>performance of the devices.<br>

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Ionic liquid lubrication at electrified interfaces

Cited by 29 publications

References 21 publications

Interfacial structuring of non-halogenated imidazolium ionic liquids at charged surfaces: effect of alkyl chain length

Interfacial structuring of non-halogenated imidazolium ionic liquids at charged surfaces: effect of alkyl chain length

Investigation of the tribological performance of ionic liquids in non-conformal EHL contacts under electric field activation

Surface confinement induces the formation of solid-like insulating ionic liquid nanostructures

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