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tribological behavior of shape memory cyanate ester materials and their tunable friction mechanism

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Friction 2023年第10期11卷 1794-1803页

作者： Zhangzhang TANG Lihe GUO Mingkun XU Hongwei RUAN Jing YANG Tingmei WANG Jianqiang ZHANG Qihua WANG Yaoming ZHANG Key Laboratory of Science and Technology on Wear and Protection of Materials Lanzhou Institute of Chemical PhysicsChinese Academy of SciencesLanzhou 730000China College of Petrochemical Technology Lanzhou University of TechnologyLanzhou 730050China Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of SciencesBeijing 100049China

High-performance polymer friction materials with tunable tribological behavior to fit varied work conditions remain a challenge of widespread interest for a variety of applications.Shape memory polymer exhibits morphing and modulus changing over temperature changing provides a promising material to adjust the friction process.Herein,we investigated the tribological properties of shape memory cyanate ester(SMCE)under different conditions.The SMCE exhibits the tribological behavior of good friction material with stable high coefficient of friction(COF)and a low wear rate.Besides,the COF increases and wear rate decreases with the temperature increasing show the tunable friction property of the SMCE.We propose a new model of wear-compensation through shape recovery to explain the adjustable friction behavior of thermal-responsive polymer from the aspect of shape recovery and energy conversion.This study provides a high-performance friction material and paves the route for the application of shape memory polymer(SMP)in tribology field with tunable property.

关键词： tribological behavior shape memory polymer cyanate ester tunable friction wear rate

tribological behavior of WC-Al_(2)O_(3)-graphene composite at different temperatures

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International Journal of Smart and Nano Materials 2022年第4期13卷 691-712页

作者： Xiaoxiao Zhang Xiaoxia Sun Yifei Wang Jiayu Qin School of Mechanical and Electrical Engineering Suqian University223800SuqianChina College of Mechanical Engineering Donghua University201620ShanghaiChina College of Mechanical Engineering University of Shanghai for Science&Technology200093ShanghaiChina

WC-Al_(2)O_(3)-graphene composite powder was synthesized by ultrasonic treatment and ball milling,then consolidated by hot pressing sintering(HPS).For potential applications,the friction coefficient and wear resistance of the sintered bulks at different temperatures(room temperature,200,400,and 600℃)were investigated.The wear tracks were characterized by scanning electron microscope,energy dispersive spectroscopy and Raman spectroscopy,X-ray photoelectron spectroscopy,respectively.The results show that the friction coefficient decreases and the wear rate increases with the increase of temperature,mainly because oxidization wear occurs on the wear surface of WC-Al_(2)O_(3)-graphene composite under high temperature.The main wear mechanism is the destruction and formation of tribochemical compacted layer.Graphene reduces the wear rate of WC-Al_(2)O_(3)-graphene composite under high tampere.The reason is that graphene reduces oxidation wear by blocking or absorbing oxygen;moreover,graphene reduces the cycle frequency of damage and reconstruction of tribochemical compacted layer by reducing the peeling of it.

关键词： WC-Al_(2)O_(3)composite graphene tribological behavior oxidization

Formulation of lyotropic liquid crystal emulsion based on natural sucrose ester and its tribological behavior as novel lubricant

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Friction 2022年第11期10卷 1879-1892页

作者： Yumei GUO Jiusheng LI Xiaojie ZHOU Yuzhao TANG Xiangqiong ZENG Laboratory for Advanced Lubricating Materials Shanghai Advanced Research InstituteChinese Academy of SciencesShanghai 201210China University of Chinese Academy of Sciences Beijing 100049China National Facility for Protein Science in Shanghai Shanghai Advanced Research InstituteChinese Academy of SciencesShanghai 201210China

The tribological behavior of oil-in-water emulsions formulated with natural lyotropic liquid crystal(LLC)emulsifiers based on natural sucrose ester was studied for the first time.Polarized optical microscopy,synchrotron radiation small-angle X-ray scattering,wide-angle X-ray scattering,and synchrotron radiation infrared microspectroscopy demonstrated that LLC emulsifiers were tightly ordered at the oil–water interface with a distinct nematic texture.The viscosity of emulsion was observed to change over time.Moreover,the zeta potential and laser particle size distribution verified the emulsion’s satisfactory stability.The frictional shearing test proved that the coefficient of friction of the emulsion versus pure oil decreased by 34.2%.The coefficient of friction of the emulsion with liquid crystal decreased 10.1%versus that without liquid crystal.Although liquid crystal emulsion did not exhibit outstanding anti-wear performance compared with pure oil,its wear volume was 29.4%less than the emulsion without liquid crystal.X-ray photoelectron spectroscopy and scanning electron microscope–energy dispersive X-ray spectroscopy(SEM–EDS)proved that the tribo-film of the emulsion with liquid crystal was formed synergistically by the liquid crystal phase with the base oil.The formulation affecting the lubricant quality was further studied by orthogonal experiments.The resulting Stribeck curve behavior suggested that proper composition with a slightly higher viscosity can better reduce friction in both boundary lubrication and mixed lubrication regimes.The lubrication mechanism indicated that the periodically ordered liquid crystal was transported to the sliding asperity in the form of emulsion droplets,which bored the pressure and released the oil to form a tribo-film.This LLC emulsion is environmentally friendly and potentially non-irritant to the skin.Thus,it has promising application prospects as novel water-based and biological lubricants.

关键词： lyotropic liquid crystal(LLC) emulsion aqueous lubrication tribological behavior

tribological behavior of nanocarbon materials with different dimensions in aqueous systems

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Friction 2020年第1期8卷 29-46页

作者： Hongmei YANG Jiusheng LI Xiangqiong ZENG Laboratory for Advanced Lubricating Materials Shanghai Advanced Research InstituteChinese Academy of SciencesUniversity of Chinese Academy of SciencesShanghai 201210China

Due to the widespread use of nanocarbon materials(NCMs),more researchers are studying their tribological performances.In this work,the tribological behaviors of the following five types of NCMs with different geometric shapes were evaluated in a novel oil‐in‐water system:spherical fullerenes(C60,0D),tubular multi‐walled carbon nanotubes(MWCNT,1D),sheet graphene oxide(GO,2D),sheet graphene oxide derivative(Oct‐O‐GO,2D),and lamellar graphite(G,3D).Among these,GO with two types of oxidation degrees,i.e.,GO(1),GO(2),and Oct‐O‐GO(1)were synthesized and characterized using Fourier‐transform infrared spectroscopy,Raman spectroscopy,x‐ray diffraction,thermogravimetric analysis,scanning electron microscopy,and contact angle measurements.The load‐carrying capacity of the NCM emulsions were evaluated using a four‐ball test machine,and the lubrication performances were investigated using a high‐frequency reciprocating friction and wear tester with a sliding distance of 1,800 mm under different loads(50 N and 100 N)at 0.5 Hz.The results revealed that the Oct‐O‐GO(1)emulsion exhibited the best load‐carrying capacity,and the best friction‐reducing and anti‐wear properties compared to other emulsions.Moreover,the anti‐wear advantage was more prominent under high load conditions,whereas the other emulsions exhibited a certain degree of abrasive or adhesive wear.The lubrication mechanism was determined through the analysis of worn surfaces using scanning electron microscopy/energy‐dispersive x‐ray spectroscopy,micro‐Raman spectroscopy,and x‐ray photoelectron spectroscopy.The results revealed that during frictional sliding,the ingredients in the emulsion can absorb and react with the freshly exposed metal surface to form surface‐active films to protect the surfaces from abrasion.Moreover,it was found that the higher the amount of ingredients that contain alkyl and O‐H/C=O,the better was the lubrication performance in addition to an increase in the carbon residue in the tribofilm generated on the meal surface.

关键词： nano‐carbon materials tribological behavior modified graphene oxide oil‐in‐water emulsion

Stable graphene oxide-based lyotropic liquid crystals for interfacial lubrication

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Friction 2024年第5期12卷 954-967页

作者： Yumei GUO Hanglin LI Jiusheng LI Xiangqiong ZENG Laboratory for Advanced Lubricating Materials Shanghai Advanced Research InstituteChinese Academy of SciencesShanghai201210China University of Chinese Academy of Sciences Beijing100049China

Lyotropic liquid crystals have lubricating properties due to their ordered assembly and fluidity,whose mesogens are often characterized by amphiphilic properties.Despite the attention that graphene oxide(GO)has been studied as a novel amphiphilic lyotropic mesogen this decade,and GO applied as a lubrication additive has been demonstrated in both oil and water-based systems,little research reveals the interfacial lubrication of GO liquid crystals yet.This work reports that GO aqueous dispersion can form lyotropic liquid crystals above a specific critical concentration of 5.00 mg/mL,providing a form of stable water-based lubricant,which can keep stable for several months and can reduce friction by 37.3%and wear by 25.24%.The liquid crystal phase was verified by polarizing microscope and synchrotron radiation small-angle X-ray scattering,and its rheological properties and viscoelasticity were studied by interfacial rheometer.The formation of lyotropic liquid crystals can enhance the stability of GO aqueous dispersions at high density,simultaneously ensuring friction decrease and anti-wear effect.It is attributed to the stable nematic network by the ordered GO sheets.The ordered assembly structure bears vertical shear force,therefore,reducing the wear.It is also assumed that the wide lateral size of graphene oxide promotes the nematic phase thus smoothes the graphene oxide film composed spontaneously under the coincidence of lamellar liquid crystal and 2D layered material.Through this work,the interlayer lubrication of GO was optimized,and the problem of GO dispersion sedimentation was solved by self-assembly.The range of interfacial lubrication of GO aqueous dispersion has been expanded and the synergistic effect is conducive to the environmentally friendly lubricants.

关键词： lyotropic liquid crystal graphene oxide aqueous lubrication tribological behavior

tribological behavior and microstructural evolution of lubricating film of silver matrix self-lubricating nanocomposite

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Friction 2021年第5期9卷 941-951页

作者： Xiao KANG Shuang YU Hailin YANG Yang SUN Lei ZHANG State Key Laboratory for Powder Metallurgy Central South UniversityChangsha 410083China Shanghai Institute of Astronautical Systems Engineering Shanghai 201108China

The aim of this study is to fabricate the nanocomposite with low friction and high wear resistance using binary solid lubricant particles.The microstructure and tribological performance of the nanocomposite are evaluated,and the composition and film thickness of the lubricating film are observed and analyzed by scanning electron microscopy(SEM)and X‐ray photoelectron spectroscopy(XPS).The nanocomposite exhibited improved tribological properties with a friction coefficient as low as 0.12 and a low wear rate of 2.17×10^(-6) mm^(3)/(N∙m)in high‐purity nitrogen atmosphere.Decreasing sliding speed can increase lubricating film thickness,and the thickest lubricating film is approximately 125 nm.As the film thickness of the lubricating film exceeded 90 nm,the friction coefficient curves became smooth.In compared with WS_(2),MoS_(2) can be more effective in forming the transfer layer on the worn surfaces at the initial stage of the tribological process.

关键词： lubricating film metal matrix self‐lubricating composite tribological behavior binary solid lubricants X‐ray photoelectron spectroscopy(XPS)

Comparative tribological behavior of friction composites containing natural graphite and expanded graphite

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Friction 2020年第4期8卷 684-694页

作者： Hongyun JIN Keke ZHOU Zhengjia JI Xiaocong TIAN Ying CHEN Luhua LU Yazhou REN Chunhui XU Shanshan DUAN Jiangyu LI Shu-en HOU Faculty of Materials Science and Chemistry China University of GeosciencesWuhan 430074China Department of Mechanical Engineering University of WashingtonSeattleWA 98195-2600USA

In this study, expanded graphite and natural graphite were introduced into resin-based friction materials, and the tribological behavior of the composites was investigated. The tribo-performance of the two friction composites was evaluated using a constant speed friction tester. The results showed that the expanded graphite composite (EGC) displayed better lubricity in both the fading and the recovery processes. The wear rate of the EGC decreased by 22.43%more than that of the natural graphite composite (NGC). In the fading process, and the EGC enhanced the stability of the coefficient of friction. The recovery maintenance rate of the NGC was 4.66% higher than that of the EGC. It can be concluded that expanded graphite plays an important role in the formation of a stable contact plateau and can effectively reduce the wear.

关键词： natural graphite expanded graphite tribological behavior wear mechanism

A molecular dynamics study on the tribological behavior of molybdenum disulfide with grain boundary defects during scratching processes

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Friction 2021年第5期9卷 1198-1212页

作者： Boyu WEI Ning KONG Jie ZHANG Hongbo LI Zhenjun HONG Hongtao ZHU Yuan ZHUANG Bo WANG School of Mechanical Engineering University of Science and Technology BeijingBeijing 100083China School of Mechanical Materials&Mechatronics EngineeringUniversity of WollongongWollongongNSW 2522Australia Beijing Institute of Spacecraft System Engineering Beijing 100094China

The effect of grain boundary(GB)defects on the tribological properties of MoS_(2) has been investigated by molecular dynamics(MD)simulations.The GB defects‐containing MoS_(2) during scratching process shows a lower critical breaking load than that of indentation process,owing to the combined effect of pushing and interlocking actions between the tip and MoS_(2) atoms.The wear resistance of MoS_(2) with GB defects is relevant to the misorientation angle due to the accumulation of long Mo-S bonds around the GBs.Weakening the adhesion strength between the MoS_(2) and substrate is an efficient way to improve the wear resistance of MoS_(2) with low‐angle GBs.

关键词： MoS_(2) grain boundary tribological behavior molecular dynamics misorientation angle

Effect of K2TiO(C2O4)2 Addition in Electrolyte on the Microstructure and tribological behavior of Micro-Arc Oxidation Coatings on Aluminum Alloy

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Acta Metallurgica Sinica(English Letters) 2017年第11期30卷 1109-1118页

作者： Jian-Li Wang Wei Yang Da-Peng Xu Xiao-Fei Yao School of Materials Science and Chemical Engineering Xi'an Technological University Xi'an 710021 China

Micro-arc oxidation （MAO） coatings with different concentrations of K2TiO（C2O4）2 in the sodium silicate base electrolyte were prepared on 6061 aluminum alloy with the aim of promoting a better understanding of the formation mechanisms and tribological behaviors of the coatings. Scanning electron microscopy （SEM） assisted with energy-dis- persive X-ray spectroscopy （EDS）, X-ray photoelectron spectroscopy （XPS） and friction test were employed to charac- terize the MAO processes and microstructure of the resultant coatings. Results showed that the composition and microstructure of the coatings were significantly affected by the addition of KETiO（CaO4）2. A sealing microstructure of MAO coating was obtained with the addition of K2TiO（C2O4）2. Ti element from K2TiO（C2O4）2 was only absorbed into the defects of micropores under surface energy in the early stage, while in the later stage, Ti element was predominant in the micropores and distributed on the coatings under plasma discharge to form TiO2. It was demonstrated that Ti and Si elements from the electrolyte could interact with each other during the MAO process and the interaction mechanism was systematically analyzed. Wear resistance of the MAO coatings with K2TiO（C2O4）2 addition was significantly improved compared with that of the MAO coatings without K2TiO（C2O4）2 addition.

关键词： Aluminum alloy Micro-arc oxidation K2TiO（C2O4）2 Coating formation mechanism tribological behavior