Co-reporter:Qiangliang Yu, Yang Wu, DongMei Li, Meirong Cai, Feng Zhou, Weimin Liu
Journal of Colloid and Interface Science 2017 Volume 487() pp:130-140
Publication Date(Web):1 February 2017
DOI:10.1016/j.jcis.2016.10.020
A new class of ionic liquid gels (ionogels) is prepared through the supramolecular self-assembly of imidazolium-based ionic liquids (ILs) bearing the urea group as gelators in normal ILs. The ILs gelator can self-assemble through hydrogen bonding and hydrophobic interaction to form analogous lamellar structures and solidify base ILs. The obtained ionogels exhibit superior anticorrosion and conductivity characteristics. Moreover, ionogels show fully thermoreversible and favorable thixotropic characteristics, such that they can be used as high-performance semisolid conductive lubricants. The tribological tests reveal that these ionogels lubricants can effectively reduce the friction of sliding pairs effectively and have better tribological performance than the pure ILs under harsh conditions. Ionogel lubricants not only maintain the excellent tribological properties and conductivity of ILs, but also prevent base liquids from creeping and leakage. Therefore, ionogel lubricants can be potentially used in the conductive parts of electrical equipments.
Co-reporter:Guowei Huang, Qiangliang Yu, Zhengfeng Ma, Meirong Cai, Weimin liu
Tribology International 2017 Volume 107() pp:152-162
Publication Date(Web):March 2017
DOI:10.1016/j.triboint.2016.08.027
•Two kinds of oil-soluble ionic liquids (ILs) with the same cation but different anions are synthesized, which exhibit more favourable solubility property in PAO10 than tradition ILs.•The tribological results indicate that the mixtures perform excellent lubricating performance compared with neat PAO10 for steel/steel contacts.•Many characterization methods, such as quartz crystal monitor (QCM), plasma treatment, external potential and X-ray photoelectron spectroscopy (XPS), are applied comprehensively to clarify the lubricating mechanism of ILs as additives.To clarify the lubricating mechanism, two kinds of oil-soluble ionic liquids (ILs) with the same cation but different anions are synthesized, and then they are added into PAO10 as additives with different mass concentration. The tribological results indicate that the mixtures perform better lubricating performance than neat PAO10 for steel/steel contacts. Then quartz crystal monitor (QCM), X-ray photoelectron spectroscopy (XPS), plasma treatment, and external potential are introduced to clarify the lubricating mechanism of ILs as additives. The lubricating mechanism of the kind of ILs can be attributed to the good adsorptivity of cations and tribochemical films on the sliding surfaces.The lubrication mechanism of ILs as the lubricant additive for the steel–steel contact.
Co-reporter:Yurong Wang, Qiangliang Yu, Meirong Cai, Lei Shi, Feng Zhou, Weimin Liu
Tribology International 2017 Volume 113(Volume 113) pp:
Publication Date(Web):1 September 2017
DOI:10.1016/j.triboint.2016.10.035
•A new [Li(non-ionic surfactant)]TFSI was prepared in-situ without the synthesis process.•The ionic liquid as additives has good solubility in water and reduces metal corrosion.•The ionic liquid can significantly improve the tribological performance of water based lubricant.•The synergy comes from the in-situ formation of ionic liquids type of complex.The paper reports the synergistic effect of lithium salt and non-ionic surfactant in improving the tribological and anticorrosion performance of water based lubricant. The synergy comes from the in-situ formation of ionic liquids type of complex. The lubricating and anti-wear behaviour of 2% lithium salt +18% non-ionic surfactants additives in water for steel/steel contacts were evaluated with lithium salt and surfactant only as the control comparisons. The tribological results show that this additive has better lubricating performance than 2% lithium salt or 20% non-ionic surfactant. The lubricating mechanism was tentatively discussed according to electrical contact resistance measurement and X-ray photoelectron spectroscopy analysis.Download high-res image (229KB)Download full-size image
Co-reporter:Guowei Huang, Qiangliang Yu, Meirong Cai, Feng Zhou, Weimin Liu
Tribology International 2017 Volume 114(Volume 114) pp:
Publication Date(Web):1 October 2017
DOI:10.1016/j.triboint.2017.04.010
•Guanidinium ionic liquids (GILs) exhibit higher temperature thermal stability than PFPE and LF106.•GILs perform excellent lubricating performance in wide temperature range (from RT to 300 °C) comparing with PFPE and LF106.•GILs also exhibit better lubricating performance than PFPE and LF106 after the high temperature treatment (200 ˚C) for 100 h.The guanidinium ionic liquids (GILs) are synthesized and have better thermal stability than perfluoropolyether (PFPE) and 1-hexyl-3-methylimidazolium bis(trifluoromethyl sulfony)imide (LF106) according to thermogravimetric analysis. GILs possess better antifriction and antiwear performance in wide temperature range (from RT to 300 °C) than PFPE and LF106. Meanwhile, GILs have the smaller weight loss and still perform good lubricating property after the treatment of high-temperature. Then, energy dispersive spectrometer (EDS), corrosion, electrochemical and quartz crystal monitor tests are carried out to investigate the influence of adsorbability of cations to the lubricating property of GILs and LF106 under different temperature conditions.Download high-res image (207KB)Download full-size image
Co-reporter:Yurong Wang;Qiangliang Yu;Lei Shi;Feng Zhou
Tribology Letters 2017 Volume 65( Issue 2) pp:
Publication Date(Web):2017 June
DOI:10.1007/s11249-017-0840-x
Ibuprofen-based (L-Ibu) halogen-free ionic liquids (ILs) were synthesized and evaluated as water-based lubricant additive. In contrast to the conventional ILs with fluoro-containing anions, the present L-Ibu ILs have no corrosive attack to steel and cast iron even in the water environment and exhibit extremely stable hydrolytic stability in water–ethylene glycol (W–EG) system. In addition, the Ibuprofen ILs as the water-based lubricant additives have better friction-reducing, extreme-pressure and antiwear properties than a commercial antiwear water-based lubricant additive of Hostagliss L4. The mechanism for excellent lubricating characteristics is investigated by combining electrical contact resistance measurement, X-ray photoelectron spectroscopy and interfacial adsorption behaviour by quartz crystal microbalance. The results indicate that a formed protective film on the contact surface prevents the direct contact of sliding pairs and contributes to the friction reduction and antiwear properties. More importantly, the prepared ILs provide a comparatively green alternative to the traditional halogenated ILs for the water-based lubrication application owing to halogen-, sulphur-, and phosphorus-free. So, these ILs are expected to develop into a highly efficient lubricant additive applied in water-based hydraulic fluids.
Co-reporter:Yurong Wang, Qiangliang Yu, Zhengfeng Ma, Guowei Huang, Meirong Cai, Feng Zhou, Weimin Liu
Tribology International 2017 Volume 112(Volume 112) pp:
Publication Date(Web):1 August 2017
DOI:10.1016/j.triboint.2017.03.034
•A N-(3-(diethoxyphosphoryl)propyl)-N,N-dimethyloctadecan- 1-ammonium bromide (NP) was synthesized.•The NP can significantly reduce the coefficient of friction to 0.076.•The NP presents remarkable extreme-pressure and abrasion resistance behaviors.•The NP significantly enhances the anti-friction capability of cationic surfactant by phosphonate functionality.A new N-(3-(diethoxyphosphoryl)propyl)-N,N-dimethyloctadecan- 1-ammonium bromide (NP) surfactant was synthesized. The NP together with 1 wt% sodium D-gluconate or 1 wt% triethanolamine displays remarkable lubricating property as the water-based lubricant additive and provides a non-corrosive environment for steel in aqueous solution. The lubricating mechanism was tentatively discussed according to electrical contact resistance, X-ray photoelectron spectroscopy and Quartz Crystal Microbalance measurement. These results show a stable protective film is formed on the contact surface by physical adsorption and tribo-chemical reactions. Surprisingly, the water-based additive has excellent anti-friction properties comparable to oil-based lubricants and superior to cationic surfactant analogue. Therefore, this NP is a potential efficient additive in water-based lubricating fluids.Download high-res image (311KB)Download full-size image
Co-reporter:Guowei Huang;Qiangliang Yu;Zhengfeng Ma;Feng Zhou
Tribology Letters 2017 Volume 65( Issue 1) pp:
Publication Date(Web):2017 March
DOI:10.1007/s11249-017-0812-1
In order to improve the tribological properties of perfluoropolyethers (PFPE), fluorinated candle soot is adopted as the lubricant additive because of their special onion-like structure. The candle soot particles (CSP) are modified by 1H,1H,2H,2H-perfluorooctanol (CSP-PFHE nanoparticles), and after the fluorination, they exhibit good dispersivity in PFPE. The mixtures composed of CSP-PFHE nanoparticles and PFPE possess better tribological performance than neat PFPE under different test conditions including variable temperature, the irradiation of atomic oxygen and extreme pressure. The reason can be attributed to that the graphene layers are exfoliated from the surfaces of nanoparticles and adhere onto the steel surfaces to form the tribofilm, which can protect the sliding pairs surfaces from friction and severe wear. Meanwhile, the redundant nanoparticles act as the rolling bearing between the sliding surfaces to decrease the wear and some are packed into the corrosion pits generated by PFPE to prevent further erosion in the process of friction. At the end, the lubricating mechanism of CSP-PFHE nanoparticles as additives of PFPE is proposed based on the test results of scanning electron microscope, contact electrical resistance and X-ray photoelectron spectroscopy.
Co-reporter:Guowei Huang;Qiangliang Yu;Feng Zhou;Weimin Liu
Advanced Materials Interfaces 2016 Volume 3( Issue 3) pp:
Publication Date(Web):
DOI:10.1002/admi.201500489
The effect of the frictional interfacial interaction of two types of gel lubricants on lubrication mechanisms is investigated. The structure of the two types of gelators, polyhydric gelator (PG) and thiol functionalized polyhydric gelator (FPG), is identical except for one of them having thiol groups. The tribological properties of these gels as lubricants are evaluated for the contacts of steel/steel, steel/aluminum, steel/copper, and steel/alumina ceramic. It is shown that these gels have better friction reduction and antiwear (AW) performance than blank 500SN. Under medium–high pressure, the gel at the interface is liquefied and a growing number of gelator molecules will adsorb onto the metal surface by polar hydroxyl and thiol headgroups. Hydroxylation treatment of sliding pairs can significantly enhance the interfacial absorption interaction and improve tribological properties. Interestingly, FPG gel lubricant exhibits better lubricating and AW properties compared with PG gel under the same test conditions. Quartz crystal microbalance (QCM) measurements suggest that FPG containing the thiol and hydroxyl dual polar groups has better adsorption ability on the contact surface than PG only with hydroxyl groups. FPG gel lubricants therefore form more robust protective films.
Co-reporter:Qiangliang Yu, Guowei Huang, Meirong Cai, Feng Zhou, Weimin Liu
Tribology International 2016 Volume 95() pp:55-65
Publication Date(Web):March 2016
DOI:10.1016/j.triboint.2015.10.032
•Novel zwitterionic gel lubricants were prepared by supramolecular assembly of low molecular weight zwitterionic gelator (ZG) in different base lubricating oils.•The dipolar structure makes ZG universal absorption ability on the various substrates.•The gel lubricants have good thermoreversibility and thixotropic characteristics.•The gel possessed better tribological properties than 500SN and Li-base grease.We report a new type of zwitterionic gelator, which cannot only gelate base lubricating oils by supramolecular self-assembly, but be used as additive in oils for significantly improved the tribological performances. The self-assembly mechanism is confirmed by NMR. The as-prepared zwitterionic gels have good thermoreversible and thixotropic characteristics, which make them as potential high performance semi-solid lubricants. The tribological results showed that the gel lubricants possessed excellent friction-reducing and anti-wear properties compared with blank 500SN and Li-base grease with 2 wt% MoS2. The morphologies of the worn surfaces were analyzed by scanning electron microscope (SEM). The lubrication mechanism is proposed according to in-situ electrical contact resistance and the surface composition analysis at the worn surfaces.Abbreviated lubrication mechanism of the gel lubricant.
Co-reporter:Qiangliang Yu;Dongmei Li;Feng Zhou;Weimin Liu
Tribology Letters 2016 Volume 61( Issue 2) pp:
Publication Date(Web):2016 February
DOI:10.1007/s11249-015-0634-y
This work presents an amino acid-derived urea as the low molecular weight gelators (LMWGs) to solidify a variety of base-lubricating oils as well as different organic solvents. LMWGs self-assemble to form fibrous structures by intermolecular hydrogen bonding and van der Waals forces, and the gelation mechanism was proposed according to the NMR analysis. The obtained gels can liquefy upon heating and gelate again after cooling down, showing reversible temperature-induced phase transition. They showed good thixotropic characteristics so that they became mobile under shearing. Therefore, it a great advantage of these supramolecular gels to be used as potential high-performance semisolid lubricants, which can guarantee both good lubrication and the ability to restrain base oil creeping, oil permeation, or leakage, especially for the gears and rolling bearings. The tribological testing results suggest that these gel lubricants could effectively reduce friction and wear of sliding pairs compared with the corresponding blank base oils and greases.
Co-reporter:Qiangliang Yu, Mingjin Fan, Dongmei Li, Zenghong Song, Meirong Cai, Feng Zhou, and Weimin Liu
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 18) pp:15783
Publication Date(Web):August 11, 2014
DOI:10.1021/am502832z
The present paper investigates a new type of thermoreversible gel lubricant obtained by supramolecular assembly of low-molecular-weight organic gelator (LMWG) in different base oils. The LMWG is a nonionic surfactant with polar headgroup and hydrophobic tail that can self-assemble through collective noncovalent intermolecular interactions (H-bonding, hydrophobic interaction) to form fibrous structures and trap base oils (mineral oils, synthetic oils, and water) in the as-formed cavities. The gel lubricants are fully thermoreversible upon heating-up and cooling down and exhibit thixotropic characteristics. This makes them semisolid lubricants, but they behave like oils. The tribological test results disclosed that the LMWG could also effectively reduce friction and wear of sliding pairs compared with base oils without gelator. It is expected that when being used in oil-lubricated components, such as gear, rolling bearing, and so on, gel lubricant may effectively avoid base oil leak and evaporation loss and so is a benefit to operation and lubrication failure for a long time.Keywords: gel lubricant; lubrication; supramolecular assembly; thermoreversible; wear
Co-reporter:Qiangbing Wei;Xiaowei Pei;Junying Hao;Feng Zhou;Weimin Liu
Advanced Materials Interfaces 2014 Volume 1( Issue 5) pp:
Publication Date(Web):
DOI:10.1002/admi.201400035
Diamond-like carbon (DLC) film has emerged as a promising material for biomedical applications, but its low tribological properties in air could not be adapted in water and biological fluids. Herein, mussel-inspired catechol adhesive is presented to functionalize DLC film and then polymer brushes are grafted by surface initiated atom transfer radical polymerization (SI-ATRP) to mimic excellent biological lubrication of articular cartilage. Macroscopic tribological evaluation demonstrates low and stable friction coefficient of polymer brushe modified DLC film in water and biological fluids when sliding with a soft polydimethylsiloxane (PDMS) hemisphere, owing to viscous fluid-like boundary lubricant film being formed by high hydration of polymer chains. The strong adhesive capability of catechol anchors also prevents polymer chains being sheared off from the substrate during friction tests. The friction responsiveness of PSPMA brushes is observed in electrolyte solution due to the conformation change of polymer chains. The successful functionalization of DLC with polymer brushes affords DLC film excellent biological lubrication and thus will broaden the scope of its applications in biomedical field.
Co-reporter:Jiaxing Wei;Feng Zhou;Weimin Liu
Tribology Letters 2014 Volume 53( Issue 3) pp:521-531
Publication Date(Web):2014 March
DOI:10.1007/s11249-013-0290-z
An onion-like carbon material was prepared from candle soot, and its tribological properties as an additive were investigated in water. The material assumed a spherical shape with a layered nanostructure based on high-resolution transmission electron microscopic analysis and had considerable sp2 hybrid carbon as revealed by Raman spectroscopy. The tribological properties were determined on an optimal SRV-IV oscillating reciprocating friction and wear tester. The results indicate that these candle soots as additives are able to effectively reduce both the friction and wear of sliding pairs in water. In addition, the chemical reactivity, physical stability, surface charge, and size of candle soot had a key impact on their lubrication properties. Based on our characterization of the wear scars by scanning electron microscopy and in situ Raman spectroscopy, we suggest a rolling and sliding lubrication mechanism.
