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: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:Guowei Huang;Qiangliang Yu;Zhengfeng Ma;Meirong Cai;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;Meirong Cai;Feng Zhou
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:Yange Feng, Youbin Zheng, Shuanhong Ma, Daoai Wang, Feng Zhou, Weimin Liu
Nano Energy 2016 Volume 19() pp:48-57
Publication Date(Web):January 2016
DOI:10.1016/j.nanoen.2015.11.017
•We fabricated PP nanowire based TENG.•The output performance was adjusted by structural control and surface functionalization.•After modified by PFTS, the device achieved a peak Voc of 1900 V and Jsc of 19 mA/m2.•The PFTS modified TENG can light up 372 commercial LEDs.•The PFTS modified TENG can power a simple temperature sensor.We report a new method to fabricate a polypropylene (PP) nanowire array based triboelectric nanogenerator (TENG) with high output through structural control and surface functionalization for harvesting friction mechanical energy. Compared with the smooth PP film based TENG, the short circuit current (Isc) and open circuit voltage (Voc) of the PP nanowire based TENGs with the nanowire diameter of about 100 nm and length of about 14 μm increase by more than 4 times. More importantly, after surface functionalization with a modifier of 1H,1H,2H,2H-perfluorooctyltrichlorosilane, the output of the PP nanowire based TENG is further increased to a maximum Voc of 1900 V and a short circuit current density of 19 mA/m2, increased by more than 100 times than that of the flat PP film based TENG. This TENG can light up 372 commercial LEDs. Furthermore, a self-powered temperature sensor is designed, which shows great potential application in daily life. By taking this simple and effective surface modification strategy, we believe various materials could be used for energy harvesting by TENGs and other devices with high performance.PP nanowire based TENGs with high output were fabricated by structural control and surface functionalization. The PP nanowire based TENG achieved a peak voltage of 1900 V and current density of 19 mA/m2 after modification with PFTS, which can light up 372 commercial LEDs and power a simple temperature sensor from room temperature to 100 oC.
Co-reporter:Xin Quan, Xiaoming Gao, Lijun Weng, Ming Hu, Dong Jiang, Desheng Wang, Jiayi Sun and Weimin Liu
RSC Advances 2015 vol. 5(Issue 80) pp:64892-64901
Publication Date(Web):17 Jul 2015
DOI:10.1039/C5RA10009G
In this paper, WS2-based solid/liquid systems were established successfully by combining pure WS2 films with FCPSO (trifluorinated-propyl and chlorinated-phenyl with methyl terminated silicone oil) and SiCH (silahydrocarbons) space oils, and the tribological performances and mechanisms were investigated. The results showed that the tribological properties of the WS2 film were improved greatly when associated with the SiCH oil, and hence this composite system exhibited a low/stable friction coefficient (<0.08) and a durable wear life (>3 × 106 sliding cycles) both in vacuum and air environments. However, the reverse effect was obtained from the WS2 film/FCPSO system. The selective adsorption of the WS2 crystallographic planes with the specific oils seemed to dominate the tribological performance of the composite systems. The SiCH and FCPSO oils have an affinity for the base and edge planes, respectively, of the WS2 films in their composite systems. The combination of the WS2 base plane with SiCH was more advantageous for the formation of perfect lubricating and transfer films at the friction contact area, resulting in improved friction and wear performances. This result provides a significant way for us to design solid/liquid lubricating systems based on lamellar solid lubricants.
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:Ming Hu, Xiaoming Gao, Lijun Weng, Jiayi Sun, Weimin Liu
Applied Surface Science 2014 Volume 313() pp:563-568
Publication Date(Web):15 September 2014
DOI:10.1016/j.apsusc.2014.06.023
Highlights
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The Ag/Cu multilayer films were prepared using magnetron sputtering technique at room temperature.
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The multilayer films had sharp interfaces between the Ag and Cu layers despite of similar crystal structure.
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The multilayer films showed improved microhardness which reached maximum value of 4.3 GPa.
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The small crystallite size and the hindering of the grain boundary sliding in Cu constituent layers were the main reasons for the hardness improvement.
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The multilayer films showed much better tribological performance than pure Ag film.
Co-reporter:Shusheng Xu, Xiaoming Gao, Ming Hu, Jiayi Sun, Dong Jiang, Desheng Wang, Feng Zhou, Lijun Weng, Weimin Liu
Applied Surface Science 2014 Volume 298() pp:36-43
Publication Date(Web):15 April 2014
DOI:10.1016/j.apsusc.2014.01.002
Highlights
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Pure WS2 and WS2-Al composite films with different structures were prepared.
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The compactness of WS2 film was significantly improved due to incorporation of Al.
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Different mechanisms of atomic oxygen resistance of both the films were discussed.
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Films before and after AO irradiation kept the unchanged tribological properties.
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The composite films showed much better wear resistance than pure WS2 film.
Co-reporter:Shusheng Xu, Xiaoming Gao, Ming Hu, Jiayi Sun, Dong Jiang, Feng Zhou, Weimin Liu, Lijun Weng
Applied Surface Science 2014 Volume 288() pp:15-25
Publication Date(Web):1 January 2014
DOI:10.1016/j.apsusc.2013.09.024
Highlights
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A novel kind of nanostructured WS2–Ni composite films was prepared.
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The introduction of dopant Ni induced the microstructural change from loose columnar platelet structure with abundant inherent porosity to denser structure.
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The WS2–Ni composite films exhibited better anti-oxidation capability compared with the pure WS2 film.
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The suitable doping of Ni in the WS2 film induced film brittleness to a lesser extent, but was able to improve adhesion strength effectively.
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The composite films with low Ni content (about 5.2 at%) showed longer wear life and about sevenfold better than that of pure WS2 film in humid air.
Co-reporter:Bowen Zhang, Daoai Wang, Bo Yu, Feng Zhou and Weimin Liu
RSC Advances 2014 vol. 4(Issue 6) pp:2586-2589
Publication Date(Web):29 Oct 2013
DOI:10.1039/C3RA42507J
A straightforward method is presented for the synthesis of onion like carbon nanoparticles from candle soot (CS) that can be used as an effective electrode material for supercapacitors. Based on well shaped candle soot, a pompom like core–shell MnO2@CS nanocomposite material was also developed to increase the specific capacitance as high as 309 F g−1.
Co-reporter:Dongmei Li, Ping Gao, Xiaojun Sun, Songwei Zhang, Feng Zhou, Weimin Liu
Tribology International 2014 Volume 73() pp:83-87
Publication Date(Web):May 2014
DOI:10.1016/j.triboint.2014.01.005
•The anti-wear and antioxidant behaviors of TEMPOs were studied for the first time.•TEMPOs as additives can improve the antiwear and antioxidant behaviors of the lubrication oils.•A TEMPOs protection film formed on the steel surface during lubrication.•TEMPOs can improve the stability of lubrication oil under atomic oxygen radiation.•TEMPOs behave as the radical quenching agents under atomic oxygen radiation.The anti-wear and antioxidant behaviors of 2,2,6,6-tetramethyl-1-piperidinooxy (TEMPO) and its derivatives were studied. The tribological properties of lubrication oils with or without the addition of TEMPOs were investigated on an Optimol SRV IV oscillating friction wear tester and the oxidative stability was evaluated by RBOT test using SH/T-0193 and ASTM D2272 procedures. The results showed that the addition of TEMPOs can improve the antiwear and antioxidant behaviors of lubrication oils remarkably. Moreover, the addition of TEMPOs can improve the performance of lubrication oil under atomic oxygen radiation.
Co-reporter:Shusheng Xu, Xiaoming Gao, Jiayi Sun, Ming Hu, Desheng Wang, Dong Jiang, Feng Zhou, Lijun Weng, Weimin Liu
Surface and Coatings Technology 2014 Volume 247() pp:30-38
Publication Date(Web):25 May 2014
DOI:10.1016/j.surfcoat.2014.03.001
•Dense WS2 based film could be acquired by the incorporation of nanoscaled Cu layers.•Deep oxidation and residual stress change led to the variation of structure for loose WS2 film.•Loose film suffered deep but not severe oxidation due to WO3 cladding protection.•Fe substrate corrosion caused the deterioration of tribological properties of loose film further.•Tribological properties of the dense multilayer film remained unchanged after storage in humid air.Pure WS2 and WS2/Cu multilayer films were deposited by radio frequency sputtering method and the erosion behavior caused by moisture was studied. For the pure WS2 film, the morphology, microstructure, composition and also the tribological properties experienced substantial change upon storage in humid air environments. Depth XPS and Raman analysis showed that the pure WS2 film suffered deep oxidation due to the open structure, but the compact WS2/Cu multilayer film resisted oxidation very well. For the multilayer film, the oxidation was restricted on the surface layer owing to the protective effect of the reactive product cladding layer of W and Cu oxidation and the compact microstructure. The open lamella structure of pure WS2 film allowed moisture to diffuse into the film interior, and so the deep oxidation, evolution of structure and Fe substrate corrosion contributed to the deterioration of tribological properties. The WS2/Cu multilayer film exhibited better deep oxidation resistance even after storage for long durations in humid air environments, and accordingly still showed low and stable friction coefficient and long wear life.
Co-reporter:Zenghong Song;Yongmin Liang;Mingjin Fan;Feng Zhou
Friction 2014 Volume 2( Issue 4) pp:392
Publication Date(Web):2014 December
DOI:10.1007/s40544-014-0066-y
Co-reporter:Shusheng Xu, Xiaoming Gao, Ming Hu, Jiayi Sun, Desheng Wang, Feng Zhou, Lijun Weng, Weimin Liu
Surface and Coatings Technology 2014 Volume 238() pp:197-206
Publication Date(Web):15 January 2014
DOI:10.1016/j.surfcoat.2013.10.074
•The WS2–Ag thin composite films with columnar structure were prepared.•Ag induced the size of platelets and pores decreased but number of those increased.•Suitable doping of Ag induced film brittleness, but improved its adhesion strength.•The composite films with low Ag content (about 9.0 at.%) showed longest wear life.•That provided a feasible way of improving wear resistance of space lubricant films.The WS2–Ag composite films were prepared by radio frequency co-sputtering method. The effects of alloying Ag content on composition, microstructure, mechanical properties and friction behaviors have been analyzed by X-ray photoelectron spectroscopy (XPS), grazing incidence X-ray diffraction (GIXRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS) and high resolution transmission electron microscope (HRTEM), scratch tester, nano-indentation tester and ball-on-disk tribo-tester. The Ag addition was in present of nanocrystalline phase in the boundary of the crystalline WS2 matrix and induced morphology change, but could not completely prevent the columnar platelets. The columnar platelet was composed of a great deal of nanocrystalline and a small amount of amorphous WS2 phase. There were no substantial variations in the hardness of the composite films when the Ag content was in the range of 0–20.3 at.%. The suitable amount of Ag content was benefited for improving the film adhesive strength and wear resistance both in vacuum and humid air environment. Particularly, the composite film with 9.0 at.% Ag exhibited the longest wear life (about 7.6 × 105 cycles in vacuum, 6.7 × 105 cycles in humid air) under high Hertzian contact pressure (as high as 1.0 GPa). The wear mechanism was discussed in terms of the rearrangement of wear track and formation of transfer film.
Co-reporter:Shusheng Xu;Xiaoming Gao;Ming Hu;Desheng Wang;Dong Jiang
Tribology Letters 2014 Volume 55( Issue 1) pp:1-13
Publication Date(Web):2014 July
DOI:10.1007/s11249-014-0322-3
To improve the tribological properties of WS2 film both in vacuum and in humid air conditions, its microstructure was optimized by doping different concentrations of Cu via radio frequency co-sputtering method. The film microstructure and composition were investigated by field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, grazing incidence X-ray diffraction and high-resolution transmission electron microscopy. It was verified that Cu was presented in amorphous phase in the WS2 matrix and could also induce amorphization and densification of the composite films gradually. The film microstructure changed from coarse columnar platelet structure at low Cu content (0–5.8 at.%) to transition structure with two separate layers at increased Cu content (11.5–16.2 at.%) and to a featureless structure at high Cu content (above 24.4 at.%). The mechanical and tribological properties of films were evaluated using the scratch tester and ball-on-disk tribometer, respectively. It was found that the incorporation of a suitable content of Cu dopant could significantly improve the film toughness, but excess amount of Cu dopant lead to high brittleness. All the composite films exhibited much lower wear rate and longer wear life than those of pure WS2 film both in vacuum and in humid air conditions. The wear mechanisms were proposed after correlating the mechanical performance with film microstructure.
Co-reporter:Jiaxing Wei;Meirong Cai;Feng Zhou
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.
Co-reporter:Guoqiang Liu, Xiaolong Wang, Feng Zhou, and Weimin Liu
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 21) pp:10842
Publication Date(Web):October 11, 2013
DOI:10.1021/am403041r
Thermoresponsive microgels, poly(N-isopropylacrylamide)-graft-poly(ethylene glycol) (PNIPAAm-g-PEG), were synthesized via emulsifier-free emulsion polymerization and the tribological property as water lubricating additive was studied. The microgels had good thermoresponsive collapse/swelling performance with lower critical solution temperature (LCST) ca. 38.4 °C. The rheological characterization and tribological tests showed that the microgels had a good lubricating performance in aqueous lubrication through interfacial physisorption and hydration lubrication, but the friction coefficient was impacted by temperature (below and above LCST). The tunable thermosensitive tribological property was attributed to the hydrophobic interaction and the enhanced interfacial absorption, which were both triggered by the elevated temperature. Furthermore, in order to avoid the water erosion in aqueous lubrication, the microgels were used together with 1H-benzotriazoles (BTA). Because of the good antifriction and anticorrosion property of BTA and the interplay between microgels and BTA, the microgels/BTA exhibited a synergistic effect in aqueous lubrication and the tribological property was more sensitive around the LCST. The present work is beneficial to understanding the tribological property of responsive microgels in aqueous lubrication and provides a novel approach for achieving low-friction through soft matters.Keywords: hydration lubrication; microgels; soft matter; thermoresponsive; tribology;
Co-reporter:Zenghong Song, Meirong Cai, Yongmin Liang, Mingjin Fan, Feng Zhou and Weimin Liu
RSC Advances 2013 vol. 3(Issue 44) pp:21715-21721
Publication Date(Web):16 Aug 2013
DOI:10.1039/C3RA42092B
Methoxy tris-ethoxy methylene benzotriazole (BTAG3) was synthesized and has good solubility in multiply-alkylated cyclopentanes (MACs) only when equal molar ratios of lithium salts, LiBF4, LiPF6, LiSO3CF3 or LiTFSI, were co-added into MACs due to the formation of ionic liquids (ILs), [Li(BTAG3)]BF4, [Li(BTAG3)]PF6, [Li(BTAG3)]SO3CF3 and [Li(BTAG3)]TFSI. The as-synthesized ILs have better solubilities in MACs than the conventional imidazolium ILs, 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (L-F108) and 1-butyl-3-methylimidazolium tetrafluoroborate (L-B104) or the unfunctionalized lithium-based IL, [Li(G3)]TFSI, which are insoluble in MACs. They were evaluated as anti-wear and anti-corrosion additive of MACs for steel–steel contact at room temperature (RT). It was found that the ILs possessed excellent friction-reducing and anti-wear properties in MACs compared with zinc dialkyldithiophosphate. Besides, the presence of benzotriazole means that these synthetic ILs have good anti-corrosion properties compared with the conventional IL, L-B104.
Co-reporter:Meirong Cai, Yongmin Liang, Feng Zhou, Weimin Liu
Wear 2013 Volume 306(1–2) pp:197-208
Publication Date(Web):30 August 2013
DOI:10.1016/j.wear.2012.09.001
Imidazolium ionic liquids (ILs) containing sterically hindered phenol and benzotriazole groups were synthesized and evaluated as combined antiwear (AW), antioxidation, and anticorrosion additive in poly(ethylene glycol) (PEG) for steel/steel contacts at room temperature and 100 °C. The physical properties of the synthetic ILs and PEG with the additive were measured. The antioxidation and anticorrosion properties of the synthetic ILs were assessed via the thermal analysis, an accelerated corrosion test and copper strip corrosion test, which showed the excellent antioxidation and anticorrosion properties in comparison with the pure PEG and the selected conventional ILs having no functional groups. Tribological results indicated that these ILs as the additives could effectively reduce friction and wear of sliding pairs in PEG. The tribological properties were generally better than the common IL (L-P106) in PEG. The wear mechanisms are tentatively discussed according to the morphology observation of worn surfaces of steel discs by scanning electron microscope (SEM) and the surface composition analysis was obtained by X-ray photoelectron spectroscopy (XPS).Highlights► Imidazolium salts bearing sterically hindered phenol and benzotriazole were synthesized. ► The imidazolium salts have combined antiwear, antioxidation and anticorrosion function. ► Synergistic effect of ionic liquid component, phenol and benzotriazole was found.
Co-reporter:Fei Li;Jun Cheng;Zhuhui Qiao;Jiqiang Ma;Shengyu Zhu;Licai Fu
Tribology Letters 2013 Volume 49( Issue 3) pp:573-577
Publication Date(Web):2013 March
DOI:10.1007/s11249-012-0101-y
It is a challenge to design self-lubricating materials that exhibit and maintain reduced friction coefficient as well as high strength over a wide range of temperatures. A high-temperature self-lubricating nickel-alloy-based composite was created using the hot pressing technique. The composite exhibited high relative density, and simultaneously superior lubricating properties, average friction coefficient below 0.25 from room temperature to 800 °C, and high strength, 470 MPa of tensile strength and 1500 MPa of compressive strength. The composite was very promising in high-temperature tribology.
Co-reporter:Junfeng Yan;Bin Li;Bo Yu; Wilhelm T. S. Huck; Weimin Liu; Feng Zhou
Angewandte Chemie International Edition 2013 Volume 52( Issue 35) pp:
Publication Date(Web):
DOI:10.1002/anie.201305978
Co-reporter:Junfeng Yan;Bin Li;Bo Yu; Wilhelm T. S. Huck; Weimin Liu; Feng Zhou
Angewandte Chemie International Edition 2013 Volume 52( Issue 35) pp:9125-9129
Publication Date(Web):
DOI:10.1002/anie.201304449
Co-reporter:MeiRong Cai;RuiSheng Guo;Feng Zhou
Science China Technological Sciences 2013 Volume 56( Issue 12) pp:2888-2913
Publication Date(Web):2013 December
DOI:10.1007/s11431-013-5403-2
Both the academic society and the industry are hunting for new energy forms for the future. However, the world should not forget the conventional technologies that contribute to the sustainable society by technical innovations. Among them, lubrication plays a significant role in energy saving and in low CO2 emission by increasing the fuel efficiency and by prolonging the service life of machines. With the advance of novel synthetic approaches, and nanoscience and technologies, novel lubrication oils and additives and their formulations are being developed to reduce friction and wear, and novel surface treatment routes and surface coatings are invented and provide more efficient lubrication. These technologies create tremendous chances for machines to work more efficiently with low energy consumption. Here we review the recent progresses and challenges associated with some novel lubrication techniques that include novel surface treatment (such as texturing, high-performance nanocomposite coatings, adapting coating), tribology design (solid and liquid lubrication), energy-conserving engine oil and novel lubricants and formula (such as ionic liquids, low S, P content additives) which are to be adopted to enhance the fuel efficiency to achieve energy saving and low carbon emission. There is increased demand to replace fossil lubricants by degradable green lubricants. Specially designed coatings can reduce drag significantly during navigation of both airplanes and ships. All these aspects will be also reviewed in the paper.
Co-reporter:Qiangbing Wei, Meirong Cai, Feng Zhou, and Weimin Liu
Macromolecules 2013 Volume 46(Issue 23) pp:9368-9379
Publication Date(Web):November 27, 2013
DOI:10.1021/ma401537j
We present a paradigm that dramatically tunes friction from superior lubrication (μ ∼ 10–3) to ultrahigh friction (μ > 1) using responsive polyelectrolyte brushes. The tunable friction is based on counterion-driven interactions in polyelectrolyte brushes that can be simply achieved by exchanging the counterions. We systematically investigated the effects of opposite counterions of different types on the friction properties of polyanionic, polycationic, and polyzwitterionic brushes. For cationic brushes with quaternary ammonium groups, the friction coefficient was progressively tuned from ∼10–3 to ∼100 according to the counterions series Cl– < ClO4– < PF6– < TFSI–. The friction of anionic brushes can be tuned by oppositely charged surfactants (tetraalkylammonium) with different length of hydrophobic tails, multivalent metal ions, and protons. The friction increase of cationic brushes is due to the dehydration and the collapse of polyelectrolyte chains induced by ion-pairing interactions. For anionic brushes, the friction increased with the length of hydrophobic tails of surfactants, which resulted from hydrophobicity induced electrostatic interaction among surfactants and polymer chains. The anionic brushes with the carboxylate and the sulfonate side groups revealed different friction responses, which is owing to the carboxylate groups getting stronger specific interaction with the quaternary ammonium and thus with the multivalent metal ions as well. The mechanism of tuning friction was finally concluded; that is, highly hydrated and swelling polymer brushes show superior lubrication, partially collapsed polymer chains have moderate lubrication, and completely dehydrated and collapsed conformation loses lubricating capability.
Co-reporter:Zenghong Song;Yongmin Liang;Mingjin Fan;Feng Zhou
Friction 2013 Volume 1( Issue 3) pp:222-231
Publication Date(Web):2013 September
DOI:10.1007/s40544-013-0019-x
Two lithium-based ionic liquids (ILs, L-C3N3, and L-P3N3) were synthesized and evaluated as novel lubricant additives for multiply alkylated cyclopentanes (MACs). They were found to be approximately 1.0% soluble in MACs at room temperature (RT), whereas traditional ILs, such as 1-ethyl-3-methylimidazolium tetrafluoroborate (L-B102), 1-hexyl-3-methylimidazolium hexafluorophosphate (L-P106), and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (L-F102), could not be dissolved in this base oil. Friction tests indicated that these ILs exhibit excellent friction-reducing and anti-wear properties both at RT and at 100 °C. They can improve the tribological properties of MACs at RT to a greater extent than the commonly used lubricant zinc dialkyldithiophosphate (T204), even at a concentration of 0.1%. The load ramp test showed that MACs with L-C3N3 and L-P3N3 also exhibit high load-carrying capabilities. Scanning electron microscope (SEM) and X-ray photoelectron spectrometer (XPS) results indicated that physical adsorption and complex tribochemical reactions occurred between the ILs and metal surfaces during the sliding process, thereby forming a surface protective film that significantly contributed to the excellent tribological properties of the new ILs.
Co-reporter:Mingjin Fan, Zenghong Song, Yongmin Liang, Feng Zhou, and Weimin Liu
ACS Applied Materials & Interfaces 2012 Volume 4(Issue 12) pp:6683
Publication Date(Web):November 27, 2012
DOI:10.1021/am3018042
A novel way of in situ forming ionic liquids (ILs) in synthetic esters is presented. Lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) can form ILs with synthetic esters, [Li(synthetic ester)]TFSI, by the donation of lone pairs on carbonyl oxygen atoms of an ester molecule to a lithium ion to form a weakly Lewis-acidic complex cation [Li(synthetic ester)]+ and following interaction with the weakly Lewis-basic anion TFSI– to generate [Li(synthetic ester)]TFSI. LiTFSI has high solubility in synthetic esters because of the complex formation. The physicochemical and tribological properties of [Li(synthetic ester)]TFSI as lubricant additives were investigated. The easy preparation, extremely good solubility and excellent tribological properties of the type of ILs make them great advantages as compared with conventional ILs that can hardly be used as lubricant additives in synthetic esters due to their low solubility. The lubrication mechanism of these ILs is tentatively discussed.Keywords: coordination; ionic liquid; lithium bis(trifluoromethylsulfonyl)imide; lubricant additive; synthetic ester;
Co-reporter:Ming Hu, Xiaoming Gao, Jiayi Sun, Lijun Weng, Feng Zhou, Weimin Liu
Applied Surface Science 2012 Volume 258(Issue 15) pp:5683-5688
Publication Date(Web):15 May 2012
DOI:10.1016/j.apsusc.2012.02.062
Abstract
The Ag film, and double layer films of Ag/Si and Ag/SiNx were deposited by magnetron sputtering technique. The atomic oxygen (AO) irradiation tests were conducted using a ground AO simulation facility. The microstructure and composition of these films before and after AO irradiation tests were analyzed using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), respectively, atomic force microscope (AFM) and scanning electron microscopy (SEM), respectively. Then the protective effects of nanoscaled amorphous Si and SiNx layers on the atomic oxygen resistant property of Ag film were investigated. The results show that nanoscaled Si or SiNx protective layer can provide better protection to Ag film against oxidation caused by AO irradiation. The silica layer formed on the surface of amorphous protective layers during AO exposure process plays the key role in protecting Ag film from oxidation. On the other hand, the tribological performance of Ag film and the multilayer films was comparatively studied using a ball-on-disc tribometer in vacuum condition. The tribotest results indicate that Ag/Si and Ag/SiNx films show the better lubricating performance before and after AO irradiation than pure Ag film.
Co-reporter:Xiaoming Gao, Jiayi Sun, Ming Hu, Lijun Weng, Feng Zhou, Weimin Liu
Applied Surface Science 2011 Volume 257(Issue 17) pp:7643-7648
Publication Date(Web):15 June 2011
DOI:10.1016/j.apsusc.2011.03.154
Abstract
Ag–Cu alloy film was deposited by arc ion plating (AIP). Atomic oxygen (AO) irradiation experiments were conducted using a ground AO simulation facility. The structure, morphology, composition and tribological property of the Ag–Cu alloy film before and after AO irradiation were investigated and compared with Ag film using X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), X-ray photoelectron spectroscope (XPS) and ball-on-disk tribometer, respectively. In depth XPS analysis clearly shows that the affected thickness of Ag–Cu alloy film was greatly reduced and the oxidation product was mainly Ag2O, but AgO and Ag2O in case of pure Ag film. As a result, the Ag–Cu alloy film exhibited better AO resistant behaviors, and showed a stable friction and low wear after the AO irradiation. The AO resistant behaviors of the Ag–Cu alloy film were discussed in terms of the film microstructure.
Co-reporter:Dongmei Li, Meirong Cai, Dapeng Feng, Feng Zhou, Weimin Liu
Tribology International 2011 Volume 44(Issue 10) pp:1111-1117
Publication Date(Web):September 2011
DOI:10.1016/j.triboint.2011.04.017
In order to improve the lubrication performance and inhibit the serious corrosivity of conventional ionic liquids (ILs) at elevated temperatures, a series of vinyl functionalized ILs were synthesized in this work. The corrosion behavior of the ILs was evaluated with copper sheet corrosion test and their tribological properties were investigated on an Optimol SRV-IV oscillating friction and wear tester at elevated temperatures. The results showed that ILs with vinyl group, such as 1-vinyl-3-butyl imidazolium tetrafluoroborate (VBImBF4), can reduce corrosion effectively and its extreme pressure reached up to 1500 N at 150 °C. Based on the XPS analysis, ILs with vinyl group could interact with the iron surface and a protecting layer would form on the surface of steel possibly. Thus, ILs lubricants with good lubricating performance and low corrosivity at elevated temperature were achieved.Highlights► A series of olefin/vinyl functionalized imidazolium ionic liquids was synthesized. ► The lubricant possesses superior corrosion resistance and high load carrying capacity. ► The good performance is ascribed to the coordination of olefin group with fresh iron. ► The strong absorption and the tribochemical reaction film lead to excellent performance.
Co-reporter:Meirong Cai;Zhu Zhao;Yongmin Liang;Feng Zhou
Tribology Letters 2010 Volume 40( Issue 2) pp:215-224
Publication Date(Web):2010 November
DOI:10.1007/s11249-010-9624-2
Five room temperature ionic liquids (ILs), 1-butyl-3-methylimidazolium hexafluorophosphate (L-P104), 1-hexyl-3-methylimidazolium hexafluorophosphate (L-P106), 1-octyl-3-methylimidazolium hexafluorophosphate (L-P108), 1-decyl-3-methylimidazolium hexafluorophosphate (L-P110), and 1-hexyl-3-methylimidazolium tetrafluoroborate (LB106) were studied as 1 wt% additives of polyurea grease for steel/steel contacts. Their tribological behaviors as additives of polyurea grease for steel/steel contacts were evaluated on an Optimol SRV-IV oscillating reciprocating friction and wear tester and an MRS-1J (G) four-ball tester at room and high temperatures. The friction test results showed that the ILs, as 1 wt% additives in polyurea grease for steel/steel contacts, had better friction reduction and anti-wear properties at high temperature than at room temperature, and ILs can significantly improve the friction reduction and anti-wear properties of polyurea grease compared with base grease containing 1 wt% of zinc dialkyldithiophosphate (T204). The excellent tribological properties are attributed to the formation of a surface protective film composed of FeF2, nitrides, and compound containing the P–O bonding on the lubricated metal surface by a tribochemical reaction. The ordered adsorbed films and good miscibility of ILs with the base grease also contributed to the excellent tribological properties. Wear mechanisms and worn steel surfaces were studied by a PHI-5702 multifunctional X-ray photoelectron spectrometer and a JSM-5600LV scanning electron microscope.
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