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Hua, J., Björling, M., Larsson, R. & Shi, Y. (2022). Controllable superlubricity achieved with mixtures of green ionic liquid and glycerol aqueous solution via humidity. Journal of Molecular Liquids, 345, Article ID 117860.
Open this publication in new window or tab >>Controllable superlubricity achieved with mixtures of green ionic liquid and glycerol aqueous solution via humidity
2022 (English)In: Journal of Molecular Liquids, ISSN 0167-7322, E-ISSN 1873-3166, Vol. 345, article id 117860Article in journal (Refereed) Published
Abstract [en]

In this work, superlubricity between steel surfaces lubricated by mixtures of [Choline][Proline] ([Cho][Pro]) ionic liquid and glycerol aqueous solution has been reached by using a rotating tribometer. Stable superlubricity could be obtained even under the humidity between 7 to 9% RH. The lowest friction is observed when the lubricant contains 3 wt.% ionic liquid. It is found that adding 3 wt.% [Cho][Pro] is helpful to maintain enough water in the steady period to retain a low viscosity. According to the calculation, the superlubricity achieved in thin film lubrication region, which is attributed to the stern layer formed by [Cho][Pro] and hydrogen-bond network that enabled a thin water layer at the interface. Interestingly, it is observed that humidity can be used to control lubrication state between superlubricity and non-superlubricity. This study provides a new method to accomplish switchable superlubricity under low humidity.

Place, publisher, year, edition, pages
Elsevier, 2022
Keywords
Glycerol, Ionic liquid, Friction control, Superlubricity
National Category
Other Mechanical Engineering
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-87675 (URN)10.1016/j.molliq.2021.117860 (DOI)000713883900051 ()2-s2.0-85118129226 (Scopus ID)
Funder
Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning, 2016-01098; 2019-00904Swedish Research Council Formas, 2017-04914; 2019-04941Swedish Energy Agency, 2018-003910
Note

Validerad;2021;Nivå 2;2021-11-08 (beamah);

Forskningsfinansiär: Mistra Innovation foundation of Sweden (MI16.23)

Available from: 2021-10-28 Created: 2021-10-28 Last updated: 2025-02-14Bibliographically approved
Hua, J., Björling, M., Larsson, R. & Shi, Y. (2022). Friction Control of Chitosan-Ag Hydrogel by Silver Ion. ES Materials & Manufacturing, 16, 30-36
Open this publication in new window or tab >>Friction Control of Chitosan-Ag Hydrogel by Silver Ion
2022 (English)In: ES Materials & Manufacturing, ISSN 2578-0611, Vol. 16, p. 30-36Article in journal (Refereed) Published
Abstract [en]

The tunable friction behavior of Chitosan (CS)-Ag hydrogel enabled by altering metal ions is evaluated. Friction control could be achieved under boundary lubrication. When adding Ag+ into a CS solution, the formed gel provided lower friction. The difference in friction coefficient between the two phases can be reversibly switched by adding Cl- or excessive Ag+ ions. It also can be found that the gel phased lubricant has a better anti-wear ability under boundary lubrication conditions. Both solution and gel typed lubricants could achieve superlubricity under elastohydrodynamic lubrication. The switchable and tunable frictional hydrogels can extend the application in the design of smart control equipment.

Place, publisher, year, edition, pages
Engineered Science Publisher, 2022
Keywords
Friction control, Hydrogel, Superlubricity
National Category
Other Mechanical Engineering Polymer Chemistry
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-93012 (URN)10.30919/esmm5f555 (DOI)2-s2.0-85136314494 (Scopus ID)
Funder
Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning, 2016-01098, 2019-00904Swedish Research Council, 2017-04914, 2019-04941Swedish Energy Agency, 2018-003910Mistra - The Swedish Foundation for Strategic Environmental Research, MI16.23
Note

Validerad;2022;Nivå 1;2022-09-13 (sofila)

Available from: 2022-09-13 Created: 2022-09-13 Last updated: 2025-02-14Bibliographically approved
Hua, J., Björling, M., Larsson, R. & Shi, Y. (2021). Controlling friction in Ionic Liquid/Glycerol Aqueous Solution lubricated contacts by adjusting CO2 and water content. Tribology International, 161, Article ID 107070.
Open this publication in new window or tab >>Controlling friction in Ionic Liquid/Glycerol Aqueous Solution lubricated contacts by adjusting CO2 and water content
2021 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 161, article id 107070Article in journal (Refereed) Published
Abstract [en]

Nowadays, the awareness for the importance of green lubricants and green lubricating additives is increasing. In this work, [Choline][Proline] ([Cho][Pro]) was added into glycerol aqueous solution to receive a high-performance green lubricant. The effect of environment condition, e.g., CO2 and water, on the green lubricant was studied. It is found that the properties of the green lubricant could be modulated by CO2 and water content. As CO2 was absorbed by the liquid, the viscosity of the liquid increased, while the viscosity of liquid diminished after adding more water. The presence of CO2 led to an obvious increase of friction. At the same time, it is also found that the friction could be altered by water content. Thus, it is possible to control friction by changing CO2 and water content.

Place, publisher, year, edition, pages
Elsevier, 2021
Keywords
Controlling friction, Ionic liquids, Glycerol, CO2
National Category
Other Mechanical Engineering
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-84295 (URN)10.1016/j.triboint.2021.107070 (DOI)000663720600003 ()2-s2.0-85107114087 (Scopus ID)
Funder
Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning, 2016-01098, 2019-00904Swedish Research Council, 2017-04914, 2019-04941Swedish Energy Agency, 2018-003910
Note

Validerad;2021;Nivå 2;2021-05-17 (beamah)

Available from: 2021-05-17 Created: 2021-05-17 Last updated: 2025-02-14Bibliographically approved
Hua, J. (2021). Friction control in different lubrication regimes. (Doctoral dissertation). Luleå: Luleå University of Technology
Open this publication in new window or tab >>Friction control in different lubrication regimes
2021 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

We often strive to minimize friction but there are also many situations where high friction is desirable. In some cases, something in between, i.e. optimum friction, is attractive. Driven by the broad application prospects, many controllable friction systems regulated with external stimuli such as solvent, pH, temperature, electric potential, and magnetic fields have been designed and fabricated. When external stimuli are imposed on the smart materials, the macroscopic physicochemical properties of the materials are dramatically changed, making controllable friction behavior to become possible. However, most of these exploratory works are in nano/micro size, which cannot be applied in macroscale for industry applications. 

Lubrication is mainly classified as three regimes: boundary, mixed and full film lubrication. If considering molecular size as well, there exists thin film lubrication between boundary lubrication and elastohydrodynamic lubrication, with the lubricating film thickness of a few nanometers to tens of nanometers. This thesis attempts to find more versatile methods of friction control and tries to find the possibility to achieve friction control at macroscale in all these lubrication regimes.

In this thesis, we investigated the possibility of adjusting friction by controlling viscosity in a lubricated contact and it was found that friction of switchable ionic liquids could be controlled in the EHL regime enabled by CO2 absorption and desorption in Paper 1. Glycerol solution formulated with ionic liquid was employed in Paper 2 to obtain superlubricity in thin film lubrication, and it was observed that the lubrication state could be switched between superlubricity and non-superlubricity by adjusting humidity. Friction control of multi-functional green lubricant in mixed lubrication was evaluated in Paper 3. Finally, the macroscopic friction control of ionic liquids in boundary lubrication enabled by environmental humidity was described in Paper 4, and stimuli responsive hydrogel also could be used for achieving friction control in boundary lubrication, studied in Paper 5.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2021
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Keywords
friciton control, glycerol, lubrication regime
National Category
Other Mechanical Engineering
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-87593 (URN)978-91-7790-964-4 (ISBN)978-91-7790-965-1 (ISBN)
Public defence
2021-12-16, E231, Luleå, 09:00 (English)
Opponent
Supervisors
Available from: 2021-10-22 Created: 2021-10-21 Last updated: 2025-02-14Bibliographically approved
Hua, J., Björling, M., Larsson, R. & Shi, Y. (2020). Controllable Friction of Green Ionic Liquids via Environmental Humidity. Advanced Engineering Materials, 22(5), Article ID 1901253.
Open this publication in new window or tab >>Controllable Friction of Green Ionic Liquids via Environmental Humidity
2020 (English)In: Advanced Engineering Materials, ISSN 1438-1656, E-ISSN 1527-2648, Vol. 22, no 5, article id 1901253Article in journal (Refereed) Published
Abstract [en]

Intelligent control of friction is an attractive but challenging topic. In this work, it is investigated if it would be possible to adjust friction in a lubricated contact by controlling environmental humidity. By exploiting the ability to adjust the environmental humidity by various saturated salt solutions, friction behavior of contacts lubricated with Choline l‐Proline ([Cho][Pro]) is modulated in a wide range of relative humidity (RH). The friction increases when the environmental humidity is increased and decreases when water is partially evaporated to a lower RH. It is thus possible to control friction by environmental humidity. The addition of water in ionic liquids (ILs) causes a decrease in viscosity, but as the tests are calculated to be performed in boundary lubrication the viscosity change is not the main factor for the change in friction. The friction sensitivity of RH can be explained by the effect of adhesion on the water uptake from humid air by [Cho][Pro]. Furthermore, the reversible changes of H‐bond types determined by the water content could be another explanation to the altered friction.

Place, publisher, year, edition, pages
John Wiley & Sons, 2020
Keywords
friction control, humidity, ionic liquids, viscosity
National Category
Other Mechanical Engineering
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-77681 (URN)10.1002/adem.201901253 (DOI)000512078300001 ()2-s2.0-85079450714 (Scopus ID)
Funder
Swedish Research Council Formas, 2016-01098Swedish Research Council, 2017-04914Swedish Energy Agency, 2018-003910
Note

Validerad;2020;Nivå 2;2020-06-03 (alebob)

Available from: 2020-02-10 Created: 2020-02-10 Last updated: 2025-02-14Bibliographically approved
Xi, Y., Hua, J. & Shi, Y. (2020). Noncontact Triboelectric Nanogenerator for Human Motion Monitoring and Energy Harvesting. Nano Energy, 69, Article ID 104390.
Open this publication in new window or tab >>Noncontact Triboelectric Nanogenerator for Human Motion Monitoring and Energy Harvesting
2020 (English)In: Nano Energy, ISSN 2211-2855, E-ISSN 2211-3282, Vol. 69, article id 104390Article in journal (Refereed) Published
Abstract [en]

Monitoring human motion and harvesting its energy is an interesting and important topic. Triboelectric nanogenerators (TENGs) have shown their potential for signal detecting and energy harvesting. In this paper, a noncontact paper-based TENG is creatively proposed to be used as a self-powered human motion monitoring sensor and also to be used for human motion energy harvesting. The noncontact mode avoids the requirement of direct physical contact between the TENG and the human subject, which fascinates the application of TENG and can increase its service life. It is found that the walking gait cycle (leg raising and falling), moving direction, walking or running speed and moving path can be reflected by the output voltage signals directly and clearly. Noncontact human motion energy harvesting is also achieved by using this TENG with a rectification circuit. It is also surprisingly found that this TENG is able to detect human motion even through a building wall, and the output voltage is strong enough to be captured by a normal multimeter without any additional amplification circuit. This study opens up a new method for self-powered noncontact human movement detecting and monitoring.

Place, publisher, year, edition, pages
Elsevier, 2020
Keywords
noncontact, self-powered, human motion monitoring, triboelectric nanogenerator, energy harvesting
National Category
Other Mechanical Engineering
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-77218 (URN)10.1016/j.nanoen.2019.104390 (DOI)000513814400044 ()2-s2.0-85076430364 (Scopus ID)
Note

Validerad;2020;Nivå 2;2020-01-27 (johcin)

Available from: 2019-12-18 Created: 2019-12-18 Last updated: 2025-02-14Bibliographically approved
Hua, J., Björling, M., Grahn, M., Larsson, R. & Shi, Y. (2019). A smart friction control strategy enabled by CO2 absorption and desorption. Scientific Reports, 9(1), Article ID 13262.
Open this publication in new window or tab >>A smart friction control strategy enabled by CO2 absorption and desorption
Show others...
2019 (English)In: Scientific Reports, E-ISSN 2045-2322, Vol. 9, no 1, article id 13262Article in journal (Refereed) Published
Abstract [en]

Intelligent control of friction is an attractive but challenging topic and it has rarely been investigated for full size engineering applications. In this work, it is instigated if it would be possible to adjust friction by controlling viscosity in a lubricated contact. By exploiting the ability to adjust the viscosity of the switchable ionic liquids, 1,8-Diazabicyclo (5.4.0) undec-7-ene (DBU)/ glycerol mixture via the addition of CO2, the friction could be controlled in the elastohydrodynamic lubrication (EHL) regime. The friction decreased with increasing the amount of CO2 to the lubricant and increased after partial releasing CO2. As CO2 was absorbed by the liquid, the viscosity of the liquid increased which resulted in that the film thickness increased. At the same time the pressure-viscosity coefficient decreased with the addition of CO2. When CO2 was released again the friction increased and it was thus possible to control friction by adding or removing CO2.

Place, publisher, year, edition, pages
Springer, 2019
National Category
Chemical Engineering Other Mechanical Engineering
Research subject
Chemical Technology; Machine Elements
Identifiers
urn:nbn:se:ltu:diva-76046 (URN)10.1038/s41598-019-49864-w (DOI)000485680900059 ()31519987 (PubMedID)2-s2.0-85072208170 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-09-18 (johcin)

Available from: 2019-09-18 Created: 2019-09-18 Last updated: 2025-02-18Bibliographically approved
Hua, J. (2019). Active friction control by using CO2 and moisture. (Licentiate dissertation). Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>Active friction control by using CO2 and moisture
2019 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Nowadays the demand for intelligent control of tribological interactions is strongly increasing in various applications. We often strive to minimize friction but there are also many situations where high friction is desirable. In some cases, something in between, i.e. optimum friction, is attractive. Driven by the broad application prospects, many controllable friction systems regulated with external stimuli such as solvent, pH, temperature, electric potential, and magnetic field have been designed and fabricated. When external stimuli are imposed on the smart materials, the macroscopic physicochemical properties of the materials are dramatically changed, making controllable friction behavior to become possible. However, most of these exploratory works are in nano/micro size and it’s difficult to use these incredible methods in macroscale directly due to that macroscopic laws of friction do not generally apply to nanoscale contacts. This thesis attempts to find more versatile methods of friction control and try to find the possibility to achieve friction control at macro-size.

Firstly, since viscosity plays an important role in elastohydrodynamic lubrication (EHL) at macro-size, it is instigated if it would be possible to adjust friction by controlling viscosity in a lubricated contact. By exploiting the ability to adjust the viscosity of the switchable ionic liquids, 1,8-Diazabicyclo (5.4.0) undec-7-ene (DBU)/ glycerol mixture via the addition of CO2, the friction could be controlled in the EHL regime (Paper Ⅰ). In order to understand more about the lubricating mechanism of DBU/glycerol/CO2 mixture, the central film thickness of the lubricants as a function of the entrainment speed was investigated.

Secondly, due to that adhesion could have influence on boundary lubrication (BL) friction at macro-size, it is investigated if it would be possible to adjust friction in a lubricated contact by controlling environmental humidity, which can alter the H-bond types, leading the change of adhesion. By exploiting the ability to adjust the environmental humidity by various saturated salt solutions, friction behavior lubricated by Choline L-Proline ([Cho][Pro]) could be modulated in a wide range of relative humidities (RH) (Paper Ⅱ).

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2019
Series
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
Keywords
friction control
National Category
Other Mechanical Engineering
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-76512 (URN)978-91-7790-488-5 (ISBN)978-91-7790-489-2 (ISBN)
Presentation
2019-12-05, E231, Luleå uninversity of technology, Luleå, 16:29 (English)
Opponent
Supervisors
Available from: 2019-10-28 Created: 2019-10-25 Last updated: 2025-02-14Bibliographically approved
Hua, J. & Shi, Y. (2019). Non-corrosive Green Lubricant With Dissolved Lignin in Ionic Liquids Behave as Ideal Lubricants for Steel-DLC Applications. Frontiers in Chemistry, 7, Article ID 857.
Open this publication in new window or tab >>Non-corrosive Green Lubricant With Dissolved Lignin in Ionic Liquids Behave as Ideal Lubricants for Steel-DLC Applications
2019 (English)In: Frontiers in Chemistry, E-ISSN 2296-2646, Vol. 7, article id 857Article in journal (Refereed) Published
Abstract [en]

Diamond-like carbon (DLC)–steel contacts become more and more popular in the industry now. Since the surface chemical properties of DLC are quite different from those of iron, traditional formulated lubricants have problems to form tribo-chemical films, which are effective to improve the tribological performance for steel-steel contacts, on the surface of DLC. Thus, new lubricants formulation strategies are needed to be considered for steel-DLC applications. A kind of green lubricant (lignin-[Choline][L-Proline] (L-[CH][Pro])) without any traditional tribo-chemical active element, i.e., free of P, S, B, etc., was studied in this paper for the steel-DLC contact. To find the difference between this new ILs and the traditional lubricants, a commercially available fully formulated lubricant was used as a reference. An Optimol SRV-III oscillating friction and wear tester was used to evaluate the tribological performance. Three different kinds of commercially available DLC coatings (Tribobond 40(Cr + a-C:H:W), Tribobond 43 [(Cr+) a-C:H), and Tribobond 44(a-C:Cr)] were investigated. The results show that the ILs exhibit an obviously lower friction coefficient than that of the traditional commercially available fully formulated lubricant. Among those three DLC coatings, the (Cr+) a-C:H DLC coating exhibits the biggest improvement of wear resistance lubricated with the new ILs than that of the commercially available fully formulated lubricant. It's expected that its excellent tribological properties are attributed to the affinity of the ILs to the metal surface and the strength of the ionic liquids interactions by hydrogen bonding. Thus, forming strong physical adsorption strategy, instead of forming chemical tribo-films, is recommended to enhance the lubricating performance of lubricants for DLC.

Place, publisher, year, edition, pages
Frontiers Media S.A., 2019
Keywords
lubricants, ionic liquids, ILs, lignin, DLC
National Category
Other Mechanical Engineering
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-77086 (URN)10.3389/fchem.2019.00857 (DOI)000504261100001 ()31867310 (PubMedID)2-s2.0-85077268948 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-12-11 (johcin)

Available from: 2019-12-06 Created: 2019-12-06 Last updated: 2025-02-14Bibliographically approved
Mu, L., Ma, X., Guo, X., Chen, M., Ji, T., Hua, J., . . . Shi, Y. (2019). Structural strategies to design bio-ionic liquid: Tuning molecular interaction with lignin for enhanced lubrication. Journal of Molecular Liquids, 280, 49-57
Open this publication in new window or tab >>Structural strategies to design bio-ionic liquid: Tuning molecular interaction with lignin for enhanced lubrication
Show others...
2019 (English)In: Journal of Molecular Liquids, ISSN 0167-7322, E-ISSN 1873-3166, Vol. 280, p. 49-57Article in journal (Refereed) Published
Abstract [en]

Lignin strengthened ionic liquids (ILs) have shown high potential to be used as high performance green lubricants. Strengthened lignin-ILs molecular interaction is an effective approach to improve their lubrication properties. The molecular interactions of ILs’ cation and anion containing different functional groups with lignin and efficiency on the lubricating properties have rarely been studied yet. In this work, a series of novel green lubricants with dissolved lignin in [Choline][Amino Acid] ([CH][AA]), [Tetramethylammonium][Glycine] ([N 1111 ][Gly]) and [Tetrabutylammonium][Glycine] ([N 4444 ][Gly]) ILs have been synthesized and their tribological properties were systematically investigated. The longer alkyl chain in cation without reciprocal H-bond interaction between ILs’ cation and anion has the positive effect on the anti-wear properties. In addition, the less steric effect and more negative natural charges of amino acid anion synergistically contribute to the stronger H-bond interaction between lignin and choline base ILs, which enhances lubrication film strength and thus resulting in the better tribological property of ILs/lignin green lubricants. Specifically, the wear volume loss of the steel disc lubricated by [N 4444 ][Gly] with the addition of 15% lignin is only 12% of the one lubricated by pure [N 4444 ][Gly]. This work presents a method to tune molecular interaction between lignin and ILs via the structural design of ILs’ cation and anion, which are revealed as the key factor that bridges the individual components and improves overall lubricating properties. 

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Amino acid, Hydrogen bond, Ionic liquids, Lignin, Lubrication, Structure
National Category
Other Mechanical Engineering
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-72933 (URN)10.1016/j.molliq.2019.02.022 (DOI)000464089800007 ()2-s2.0-85061426516 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-02-18 (svasva)

Available from: 2019-02-18 Created: 2019-02-18 Last updated: 2025-02-14Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-8157-4644

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