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Watanabe, Seiya
Publications (10 of 10) Show all publications
Rohlmann, P., Black, J. J., Watanabe, S., Leckner, J., Shimpi, M. R., Rutland, M. W., . . . Glavatskih, S. (2023). Tribochemistry of imidazolium and phosphonium bis(oxalato)borate ionic liquids: Understanding the differences. Tribology International, 181, 108263, Article ID 108263.
Open this publication in new window or tab >>Tribochemistry of imidazolium and phosphonium bis(oxalato)borate ionic liquids: Understanding the differences
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2023 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 181, p. 108263-, article id 108263Article in journal (Refereed) Published
Abstract [en]

Lubrication properties of imidazolium and phosphonium bis(oxalato)borate ionic liquids (ILs) are compared in a reciprocating sliding contact at 80 degrees C and 140 degrees C. Both the influence of the alkyl chain length and the cation architecture on friction, wear and lubricant breakdown are investigated. Imidazolium ILs showed lower friction than phosphonium ILs though only phosphonium-based ILs reduced wear. A longer alkyl chain reduced friction only in the case of the imidazolium-based ILs. Analysis of the wear scars was consistent with chemical breakdown solely of the anion. Chemical changes in the ILs after the tribotests were more pronounced for imidazolium-based ILs, and comparison of breakdown and tribofilm formation implicated catalysis by the imidazolium center, which, in turn, had a strong dependence on the surface self-assembly.

Place, publisher, year, edition, pages
Elsevier BV, 2023
Keywords
Ionic liquid, Friction, Wear, Decomposition, Tribofilm, ToF-SIMS
National Category
Other Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-324650 (URN)10.1016/j.triboint.2023.108263 (DOI)000935164000001 ()2-s2.0-85147357958 (Scopus ID)
Note

QC 20230309

Available from: 2023-03-09 Created: 2023-03-09 Last updated: 2025-02-14Bibliographically approved
Rohlmann, P., Watanabe, S., Shimpi, M. R., Leckner, J., Rutland, M. W., Harper, J. B. & Glavatskih, S. (2021). Boundary lubricity of phosphonium bisoxalatoborate ionic liquids. Tribology International, 161, Article ID 107075.
Open this publication in new window or tab >>Boundary lubricity of phosphonium bisoxalatoborate ionic liquids
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2021 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 161, article id 107075Article in journal (Refereed) Published
Abstract [en]

The lubricating performance of trihexyl(tetradecyl)phosphonium bisoxalatoorthoborate (P-BOB) ionic liquid is analysed at 80 degrees C and 140 degrees C, and compared to an ionic liquid containing a partially hydrated version of the anion. The reduction of the anions produces oxalate complexes that contribute synergistically to lower friction. The role of oxalate in enhancing lubricity was indicated by the fact that the partially hydrated anion is a precursor orthoborate anion complexed with oxalic acid. It consequently showed the lowest friction at 80 degrees C. Upon heating, the precursor was converted into [BOB]- and displayed the same friction at 140 degrees C as the fully synthesised species. The mechanisms of the breakdown of the [BOB]- anion and formation of the tribofilm are elucidated.

Place, publisher, year, edition, pages
Elsevier BV, 2021
Keywords
Orthoborate, Oxalate, Friction, Wear
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-298666 (URN)10.1016/j.triboint.2021.107075 (DOI)000663722500004 ()2-s2.0-85106485187 (Scopus ID)
Note

QC 20210720

Available from: 2021-07-20 Created: 2021-07-20 Last updated: 2024-04-02Bibliographically approved
Pilkington, G., Welbourn, R., Oleshkevych, A., Watanabe, S., Pedraz, P., Radiom, M., . . . Rutland, M. W. (2020). Effect of water on the electroresponsive structuring and friction in dilute and concentrated ionic liquid lubricant mixtures. Physical Chemistry, Chemical Physics - PCCP, 22(48), 28191-28201
Open this publication in new window or tab >>Effect of water on the electroresponsive structuring and friction in dilute and concentrated ionic liquid lubricant mixtures
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2020 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 22, no 48, p. 28191-28201Article in journal (Refereed) Published
Abstract [en]

The effect of water on the electroactive structuring of a tribologically relevant ionic liquid (IL) when dispersed in a polar solvent has been investigated at a gold electrode interface using neutron reflectivity (NR). For all solutions studied, the addition of small amounts of water led to clear changes in electroactive structuring of the IL at the electrode interface, which was largely determined by the bulk IL concentration. At a dilute IL concentration, the presence of water gave rise to a swollen interfacial structuring, which exhibited a greater degree of electroresponsivity with applied potential compared to an equivalent dry solution. Conversely, for a concentrated IL solution, the presence of water led to an overall thinning of the interfacial region and a crowding-like structuring, within which the composition of the inner layer IL layers varied systematically with applied potential. Complementary nanotribotronic atomic force microscopy (AFM) measurements performed for the same IL concentration, in dry and ambient conditions, show that the presence of water reduces the lubricity of the IL boundary layers. However, consistent with the observed changes in the IL layers observed by NR, reversible and systematic control of the friction coefficient with applied potential was still achievable. Combined, these measurements provide valuable insight into the implications of water on the interfacial properties of ILs at electrified interfaces, which inevitably will determine their applicability in tribotronic and electrochemical contexts.

Place, publisher, year, edition, pages
Royal Society of Chemistry (RSC), 2020
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-289267 (URN)10.1039/d0cp05110a (DOI)000603167900024 ()33295339 (PubMedID)2-s2.0-85098937782 (Scopus ID)
Note

QC 20210127

Available from: 2021-01-27 Created: 2021-01-27 Last updated: 2024-04-02Bibliographically approved
Pilkington, G., Oleshkevych, A., Pedraz, P., Watanabe, S., Radiom, M., Reddy, A. B., . . . Rutland, M. W. (2020). Electroresponsive structuring and friction of a non-halogenated ionic liquid in a polar solvent: effect of concentration. Physical Chemistry, Chemical Physics - PCCP, 22(34), 19162-19171
Open this publication in new window or tab >>Electroresponsive structuring and friction of a non-halogenated ionic liquid in a polar solvent: effect of concentration
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2020 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 22, no 34, p. 19162-19171Article in journal (Refereed) Published
Abstract [en]

Neutron reflectivity (NR) measurements have been employed to study the interfacial structuring and composition of electroresponsive boundary layers formed by an ionic liquid (IL) lubricant at an electrified gold interface when dispersed in a polar solvent. The results reveal that both the composition and extent of the IL boundary layers intricately depend on the bulk IL concentration and the applied surface potential. At the lowest concentration (5% w/w), a preferential adsorption of the IL cation at the gold electrode is observed, which hinders the ability to electro-induce changes in the boundary layers. In contrast, at higher IL bulk concentrations (10 and 20% w/w), the NR results reveal a significantly larger concentration of the IL ions at the gold interface that exhibit significantly greater electroresponsivity, with clear changes in the layer composition and layer thickness observed for different potentials. In complementary atomic force microscopy (AFM) measurements on an electrified gold surface, such IL boundary layers are demonstrated to provide excellent friction reduction and electroactive friction (known as tribotronics). In agreement with the NR results obtained, clear concentration effects are also observed. Together such results provide valuable molecular insight into the electroactive structuring of ILs in solvent mixtures, as well as provide mechanistic understanding of their tribotronic behaviours.

Place, publisher, year, edition, pages
Royal Society of Chemistry (RSC), 2020
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-283279 (URN)10.1039/d0cp02736g (DOI)000567772700036 ()32812565 (PubMedID)2-s2.0-85090870483 (Scopus ID)
Note

QC 20201006

Available from: 2020-10-06 Created: 2020-10-06 Last updated: 2024-04-02Bibliographically approved
Watanabe, S., Pilkington, G., Oleshkevych, A., Pedraz, P., Radiom, M., Welbourn, R., . . . Rutland, M. W. (2020). Interfacial structuring of non-halogenated imidazolium ionic liquids at charged surfaces: effect of alkyl chain length. Physical Chemistry, Chemical Physics - PCCP, 22(16), 8450-8460
Open this publication in new window or tab >>Interfacial structuring of non-halogenated imidazolium ionic liquids at charged surfaces: effect of alkyl chain length
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2020 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 22, no 16, p. 8450-8460Article in journal (Refereed) Published
Abstract [en]

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 non-halogenated 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.

Place, publisher, year, edition, pages
Royal Society of Chemistry (RSC), 2020
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-276918 (URN)10.1039/d0cp00360c (DOI)000537175100016 ()32271337 (PubMedID)2-s2.0-85084167320 (Scopus ID)
Note

QC 20200622

Available from: 2020-06-22 Created: 2020-06-22 Last updated: 2024-04-02Bibliographically approved
Kawada, S., Watanabe, S., Tadokoro, C. & Sasaki, S. (2018). Effects of Alkyl Chain Length of Sulfate and Phosphate Anion-Based Ionic Liquids on Tribochemical Reactions. Tribology letters, 66(1), Article ID 8.
Open this publication in new window or tab >>Effects of Alkyl Chain Length of Sulfate and Phosphate Anion-Based Ionic Liquids on Tribochemical Reactions
2018 (English)In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 66, no 1, article id 8Article in journal (Refereed) Published
Abstract [en]

Ionic liquids are expected to become increasingly popular lubricants as they feature a number of attractive properties. This investigation focused on sulfate and phosphate anion-based ionic liquids and the improvement in lubricating performance with the addition of these anions. However, the detailed lubricating mechanism and effect of alkyl chain length on tribochemical reactions are unclear. This study investigates tribochemical reaction processes using a quadrupole mass spectrometer (Q-MS) and X-ray photoelectron spectroscopy. Seven types of ionic liquids: 1-ethyl-3-methylimidazolium hydrogensulfate ([EMIM][HSO4]), 1-ethyl-3-methylimidazolium methylsulfate ([EMIM][MSU]), 1-ethyl-3-methylimidazolium ethylsulfate ([EMIM][ESU]), 1-ethyl-3-methylimidazolium n-octylsulfate ([EMIM][OSU]), 1-ethyl-3-methylimidazolium dimethyl phosphate ([EMIM][DMP]), 1-ethyl-3-methylimidazolium diethyl phosphate ([EMIM][DEP]), and 1-ethyl-3-methylimidazolium dibutyl phosphate ([EMIM][DBP]), were selected as lubricants. The friction coefficient of sulfate anion-based ionic liquids increased as their alkyl chain lengthened. However, wear scar diameter in this case showed the opposite tendency. The friction coefficient and wear scar diameter of phosphate anion-based ionic liquids increased with an increase in the alkyl chain length. Q-MS results indicated that the main outgassing components during sliding were the cation components, whereas the anion remained on the sliding surface and formed a tribofilm. The ionic liquids with short alkyl chains reacted with the sliding surface easily and led to very low friction. However, corrosive wear occurred in the case of the sulfate anion. On the other hand, anions with long alkyl chains underwent gradual tribochemical reactions because that led the mitigation of contact with nascent surface. The phosphate-based ionic liquids with long alkyl chains were unable to cause the lubricating effect due to low reactivity.

Place, publisher, year, edition, pages
Springer-Verlag New York, 2018
Keywords
Ionic liquids, Phosphate, Quadrupole mass spectrometer, Sulfate, Tribochemical reaction
National Category
Other Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-220192 (URN)10.1007/s11249-017-0962-1 (DOI)000426475600024 ()2-s2.0-85037054268 (Scopus ID)
Note

QC 20171218

Available from: 2017-12-18 Created: 2017-12-18 Last updated: 2025-02-14Bibliographically approved
Kawada, S., Watanabe, S., Sasaki, S. & Miyatake, M. (2018). Evaluation of friction behavior and surface interactions of cyano-based ionic liquids under different sliding contacts and high vacuum condition. Lubricants, 6(3), Article ID 69.
Open this publication in new window or tab >>Evaluation of friction behavior and surface interactions of cyano-based ionic liquids under different sliding contacts and high vacuum condition
2018 (English)In: Lubricants, ISSN 2075-4442, Vol. 6, no 3, article id 69Article in journal (Refereed) Published
Abstract [en]

The friction coefficients of ionic liquids were evaluated by many investigations. Most investigations used fluorine-based ionic liquids as lubricants. However, these ionic liquids produce the corrosion wear. This investigation focuses on the use of cyano-based ionic liquids as lubricants. Compared to fluorine-based ionic liquids, cyano-based ionic liquids exhibit high friction coefficients against steel material. This work examines how the friction coefficients of cyano-based ionic liquids are influenced by the type of sliding material used (AISI 52100, TiO2, and tetrahedral amorphous carbon). TiO2 lubricated with 1-ethyl-3-methylimidazolium tricyanomethanide, and ta-C lubricated with 1-butyl-1methylpyrrolidinium tetracyanoborate exhibited very low friction coefficients, smaller than fluorine-based ionic liquids. Time-of-Flight Secondary Ion Mass Spectrometry analysis showed that anions adsorb onto the worn surface, suggesting that anion adsorption is a critical parameter influencing friction coefficients. Quadrupole Mass Spectrometry measurements revealed that cations decompose on the nascent surface, preventing adsorption on the worn surface. These results suggest that low friction coefficients require the decomposition of cations and adsorption of anions. The reactivity of nascent surface changes with the sliding material used due to varying catalytic activity of the nascent surfaces.

Place, publisher, year, edition, pages
MDPI AG, 2018
Keywords
Cyano-based ionic liquids, Quadrupolemass spectrometer, Tribo-chemical reaction, Vacuum
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-247197 (URN)10.3390/lubricants6030069 (DOI)000448335500013 ()2-s2.0-85056378000 (Scopus ID)
Note

QC 20190423

Available from: 2019-04-23 Created: 2019-04-23 Last updated: 2022-06-26Bibliographically approved
Abbott, A., Liu, S., Rutland, M. W., Watanabe, S. & Wishart, J. (2018). Ionic liquids at interfaces: general discussion. Faraday discussions, 206, 549-586
Open this publication in new window or tab >>Ionic liquids at interfaces: general discussion
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2018 (English)In: Faraday discussions, ISSN 1359-6640, E-ISSN 1364-5498, Vol. 206, p. 549-586Article in journal, Editorial material (Other academic) Published
Place, publisher, year, edition, pages
Royal Society of Chemistry (RSC), 2018
National Category
Other Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-303469 (URN)10.1039/C7FD90094E (DOI)000418096900029 ()29199731 (PubMedID)2-s2.0-85038396580 (Scopus ID)
Note

QC 20211014

Available from: 2021-10-14 Created: 2021-10-14 Last updated: 2025-02-14Bibliographically approved
Kawada, S., Watanabe, S., Tadokoro, C., Tsuboi, R. & Sasaki, S. (2018). Lubricating mechanism of cyano-based ionic liquids on nascent steel surface. Tribology International, 119, 474-480
Open this publication in new window or tab >>Lubricating mechanism of cyano-based ionic liquids on nascent steel surface
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2018 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 119, p. 474-480Article in journal (Refereed) Published
Abstract [en]

This study investigates the lubricating mechanism of cyano-based ionic liquids on steel surfaces using Q-MS, ToF-SIMS, and TGA. [EMIM][DCN], [EMIM][TCC], [EMIM][TCB], [BMPL][DCN], [BMPL][TCC], and [BMPL][TCB] were selected as lubricants. [EMIM][TCB] exhibited the highest friction coefficient. The others exhibited very low friction coefficients of less than 0.08. Q-MS analysis indicated that the cation components were detected in outgassing during sliding tests. However, anion components were not detected. ToF-SIMS results showed that the anions remained on the worn surfaces which would lead low friction coefficients. To achieve low friction coefficient, the tribo-decomposition of the ionic liquids and adsorption of anion were required. TGA indicated thermal stability was an index for tribo-decomposition on the nascent steel surface.

Place, publisher, year, edition, pages
Elsevier Ltd, 2018
Keywords
Ionic liquids, Q-MS, TGA, ToF-SIMS, Ions, Liquids, Lubrication, Negative ions, Secondary ion mass spectrometry, Tribology, Friction coefficients, Low friction coefficients, Lubricating mechanism, Sliding test, Steel surface, ToF SIMS, Worn surface, Friction
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-223132 (URN)10.1016/j.triboint.2017.11.019 (DOI)000424960500045 ()2-s2.0-85034861265 (Scopus ID)
Note

Export Date: 13 February 2018; Article; CODEN: TRBIB; Correspondence Address: Kawada, S.; Graduate School of Tokyo University of Science, Department of Mechanical EngineeringJapan; email: 4515702@ed.tus.ac.jp; Funding details: 15J05958, JSPS, Japan Society for the Promotion of Science; Funding details: JP26630041; Funding details: JP16H02310. QC 20180327

Available from: 2018-03-27 Created: 2018-03-27 Last updated: 2022-06-26Bibliographically approved
Kawada, S., Sato, K., Watanabe, S. & Sasaki, S. (2017). Lubricating property of cyano-based ionic liquids against hard materials. Journal of Mechanical Science and Technology, 31(12), 5745-5750
Open this publication in new window or tab >>Lubricating property of cyano-based ionic liquids against hard materials
2017 (English)In: Journal of Mechanical Science and Technology, ISSN 1738-494X, E-ISSN 1976-3824, Vol. 31, no 12, p. 5745-5750Article in journal (Refereed) Published
Abstract [en]

Ionic liquids are expected to be used as a new lubricants and lubricant additives because of their unique properties. However, cyano-based ionic liquids have exhibited poor lubricating property with steel/steel contacts. We evaluated the lubricating properties of cyano-based ionic liquids with steel/hard materials contacts. TiO2, Al2O3, and tetrahedral amorphous carbon (ta-C) DLC were used as hard materials. Six types of ionic liquids, as combination of two types of cations ([EMIM], [BMPL]) and three types of cyanide anions ([DCN], [TCC] and [TCB]), were selected. In sliding tests of steel/TiO2 and steel/Al2O3 lubricated with [EMIM][DCN], [BMPL][DCN], [EMIM][TCC], [BMPL][TCC] exhibited low friction coefficients of less than 0.1. In addition, steel/Al2O3 and steel/ta-C DLC lubricated with [BMPL][TCB] exhibited very low friction coefficients less than 0.05. On the other hand, high friction coefficients were observed at steel/TiO2 and steel/Al2O3 contacts lubricated with [EMIM][TCB] and steel/ta-C DLC contact lubricated with [EMIM] cation group. Peeling of the ta-C DLC was observed when [EMIM] cation group was used. ToF-SIMS analysis indicated that the anion was adsorbed on the worn surfaces in the case of low frictional conditions. However, both ions were hardly observed in the case of high frictional conditions. It is considered that the ionic liquids underwent tribo-decomposition on the worn surfaces at low friction coefficient. To evaluate the degree of tribo-decomposition, Thermogravimetric analysis (TGA) was used. TGA results indicated that [EMIM][TCB], which exhibited high friction coefficient, had the most highest stability among all ionic liquids. Low stability ionic liquids, however, showed a tendency for low friction coefficient. These results suggest that lubricating properties are related to the stability of ionic liquids.

Place, publisher, year, edition, pages
KOREAN SOC MECHANICAL ENGINEERS, 2017
Keywords
Ceramics, DLC, Ionic liquids, TGA, ToF-SIMS, Vacuum
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-220843 (URN)10.1007/s12206-017-1116-y (DOI)000418144900016 ()2-s2.0-85038128980 (Scopus ID)
Note

QC 20180111

Available from: 2018-01-11 Created: 2018-01-11 Last updated: 2022-06-26Bibliographically approved
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