Lubrication Mechanism of Halogen-Free Ionic Liquids

Kawada, Shouhei; Watanabe, Seiya; Tsuboi, Ryo; Sasaki, Shinya; Prakash, Braham

doi:10.2474/trol.12.155

Cited by 14 publications

(16 citation statements)

References 27 publications

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“…In this study, the reduction in friction between steel disks lubricated with (BMIM)(DCN) and (BMIM)(TCC) was confirmed at 90 • C and 170 • C, respectively. With regard to the friction reduction mechanism of DLC, graphitization of DLC at the friction interface has been pointed out as the cause [31][32][33][34][35][36]. The results of Raman spectroscopy indicated that the graphitization of the ta-C film progressed on the worn surface at the temperature corresponding to the low friction coefficient, which affected the friction behavior.…”

Section: Discussionmentioning

confidence: 99%

“…MALDI-TOF/MS analyses indicated that the anions from the ionic liquid adsorbed on the worn surface at the temperature corresponding to the low friction coefficient. The presence of anions on the worn surface and the reduction in friction due to the adsorbed anions have often been reported [19,20,32,37,38]. It has been reported that the ta-C film surface is reactive due to the presence of dangling bonds and reacts with the lubricants [31].…”

Section: Discussionmentioning

confidence: 99%

“…Diamond-like carbon (DLC) is also used as one of the effective friction materials for reducing friction between surfaces [29,30]. Lubricating properties of cyano-based ionic liquids in steel/DLC and DLC/DLC contacts have been evaluated, and these combinations have been reported to exhibit low friction [17,20,[31][32][33]. Further, AISI52100/tetrahedral amorphous carbon (ta-C) film and ta-C film/ta-C film contacts exhibited very low friction of 0.02 and 0.018, respectively.…”

Section: Introductionmentioning

confidence: 99%

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Lubricating Properties of Cyano-Based Ionic Liquids against Tetrahedral Amorphous Carbon Film

et al. 2020

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Ionic liquids have unique characteristics, which render them ideal candidates as new base oils or additives. In particular, there are great expectations from the combination of diamond-like carbon and cyano-based ionic liquids. Lubricating properties of cyano-based ionic liquids have been studied on specific tetrahedral amorphous carbon (ta-C) films. After lubrication, ta-C film/ta-C film contact interface exhibits exceedingly low friction. Therefore, it is necessary to understand this low friction phenomenon. The current study evaluated the lubricating mechanism of cyano-based ionic liquids against ta-C films. 1-Butyl-3-methylimidazolium dicyanamide ((BMIM)(DCN)) and 1-butyl-3-methylimidazolium tricyanomethane ((BMIM)(TCC)) were used as lubricants, with the latter exhibiting low friction coefficient of 0.03. Steel cylinders and disks with ta-C films were used as test specimens. Raman spectroscopy, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, and thermogravimetric analysis (TGA) helped us understand the mechanism of low friction induced by (BMIM)(TCC). Graphitization of the ta-C film at high temperatures might have caused the reduction in friction between the films. Similarly, anion adsorption on the worn surface at high temperatures also led to reduced friction. However, the TGA result showed a different trend than that of the sliding test. Our results indicate that the cyano-based ionic liquids underwent tribo-decomposition at low temperatures. Further, a minimum temperature was required for the adsorption of anions onto the sliding surface.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Lubricating Properties of Cyano-Based Ionic Liquids against Tetrahedral Amorphous Carbon Film

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“…Especially, the specific wear rate of halogen-free ionic liquids is very large even with low friction (Kawada et al, 2018b). Another effective means is to use sliding materials made of hard materials (Kawada et al, 2017a), (Kondo et al, 2013). Ceramics, nitrogen coating, and diamond-like carbon (DLC) improve the tribological performances of halogen-free ionic liquids.…”

Section: Introductionmentioning

confidence: 99%

Tribological performances of halogen-free ionic liquids against a-C:H and ta-C films under vacuum

Kawada

Sasaki

Miyatake

2020

JAMDSM

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Ionic liquids have high potential as novel lubricants because of their unique physical properties. In particular, halogen-free ionic liquids are low environmental-load lubricants. Unfortunately, these ionic liquids exhibit a poor tribological performance against bearing steel. However, they exhibit high performances against diamondlike carbon (DLC) under the high vacuum condition. The influence of DLC species on tribological performances and the reaction mechanism of halogen-free ionic liquids on the worn surface are still unknown. This investigation evaluates the tribological performances of halogen-free ionic liquids (1-ethyl-3methylimidazolium dicyanamide ([EMIM][DCN]), 1-ethyl-3-methylimidazolium tricyanomethane ([EMIM][TCC]), and 1-ethyl-3-methylimidazolium tetracyanoborate ([EMIM][TCB])) against two types of DLC (tetrahedral amorphous carbon (ta-C) and hydrogenated amorphous carbon (a-C:H)). The tribological performances of ionic liquids differed by the anion structure and the type of DLCs. The DLCs lubricated with [EMIM][DCN] and ta-C lubricated with [EMIM][TCC] exhibited a low friction coefficient. On the other hand, other ionic liquids exhibited the high friction coefficients against DLCs. A time-of-flight secondary-ion mass spectrometer analysis indicated that the tribo-decomposition of halogen-free ionic liquids and the adsorption of anion achieve a low friction. The chemical activity of nascent surfaces plays a very important role in achieving tribo-decomposition. However, because this activity of DLC was lower than that of bearing steel, [EMIM][TCC] exhibited a poor tribological performance. Thus, although the tribological performances of halogen-free ionic liquids can be improved by using DLC as sliding materials, there is also the possibility of inhibiting the formation of an adsorption layer derived from ionic liquids.

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“…Especially, tetrafluoroborate and hexafluorophosphate undergo hydrolysis when exposed to moisture and generate hydrogen fluoride even without sliding [25][26][27]. To prevent corrosion, use of fluorinefree ionic liquids, such as bis(oxalato)borate, ethylsulfate, diethylphosphate, dicyandiamide, tricyanomethane, and tetracyanoborate has been explored [28][29][30][31][32][33]. These ionic liquids do not have fluorine in their chemical strucutres, and therefore, they have a low risk of corrosion damage.…”

Section: Introductionmentioning

confidence: 99%

Tribological Properties of Cyano-Based Ionic Liquids under Different Environments

Kawada

Sasaki

2018

Tribology Online

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Ionic liquids have been used as novel high-performance lubricants. However, fluorine-based ionic liquids cause corrosion of materials by the formation of FeF 2 and FeF 3 . This study focuses on cyano-based ionic liquids, as they have low corrosion tendencies owing to the absence of fluorine in their structures. However, cyano-based ionic liquids are hydrophilic, and hence, the effect of ambient conditions (e.g., atmospheric moisture) on the tribological properties needs to be investigated. This study reports the tribological properties of two types of cyano-based ionic liquids 1-ethyl-3-methylimidazolium dicyanamide and 1-ethyl-3-methylimidazolium tricyanomethane under air, vacuum, and dry air environments. Their friction coefficients were found to be dependent on the ambient condition. Both the ionic liquids exhibited low friction coefficients in vacuum. The time-of-flight secondary ion mass spectrometry results indicated that the anion was adsorbed on the worn surface under vacuum conditions, and the adsorbed anion exhibited a low friction. In dry air, the cation was adsorbed on the worn surface, and the adsorbed cation exhibited a higher friction coefficient than the adsorbed anion. In air, the cyano-based ionic liquids caused corrosion of the sliding material and exhibited a high friction coefficient, because of the absorption of moisture from air.

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Lubrication Mechanism of Halogen-Free Ionic Liquids

Cited by 14 publications

References 27 publications

Lubricating Properties of Cyano-Based Ionic Liquids against Tetrahedral Amorphous Carbon Film

Lubricating Properties of Cyano-Based Ionic Liquids against Tetrahedral Amorphous Carbon Film

Tribological performances of halogen-free ionic liquids against a-C:H and ta-C films under vacuum

Tribological Properties of Cyano-Based Ionic Liquids under Different Environments

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