Graphene as a lubricating additive holds great potential for industrial lubrication. However, its poor dispersity and compatibility with base oils and grease hinder maximizing performance. Here, the infuence of graphe...Graphene as a lubricating additive holds great potential for industrial lubrication. However, its poor dispersity and compatibility with base oils and grease hinder maximizing performance. Here, the infuence of graphene dispersion on the thickening efect and lubrication function is considered. A well-dispersed lubricant additive was obtained via trihexyl tetradecyl phosphonium bis(2-ethylhexyl) phosphate modifed graphene ([P_(66614)][DEHP]-G). Then lithium complex grease was prepared by saponifcation with 12-OH stearic acid, sebacic acid, and lithium hydroxide, using polyalphaolefn (PAO20) as base oil and the modifed-graphene as lubricating additive, with the original graphene as a comparison. The physicochemical properties and lubrication performance of the as-prepared greases were evaluated in detail. The results show that the as-prepared greases have high dropping point and colloidal stability. Furthermore, modifed-graphene lithium complex grease ofered the best friction reduction and anti-wear abilities, manifesting the reduction of friction coefcient and wear volume up to 18.84% and 67.34%, respectively. With base oil overfow and afux, well-dispersed [P_(66614)][DEHP]-G was readily adsorbed to the worn surfaces, resulting in the formation of a continuous and dense graphene deposition flm. The synergy of deposited graphene-flm, spilled oil, and adhesive grease greatly improves the lubrication function of grease. This research paves the way for modulating high-performance lithium complex grease to reduce the friction and wear of movable machinery.展开更多
In order to improve the curving performance of the conventional wheelset in sharp curves and resolve the steering ability problem of the independently rotating wheel in large radius curves and tangent lines, a differe...In order to improve the curving performance of the conventional wheelset in sharp curves and resolve the steering ability problem of the independently rotating wheel in large radius curves and tangent lines, a differential cou- pling wheelset （DCW） was developed in this work. The DCW was composed of two independently rotating wheels （IRWs） coupled by a clutch-type limited slip differential. The differential contains a static pre-stress clutch, which could lock both sides of IRWs of the DCW to ensure a good steering performance in curves with large radius and tangent track. In contrast, the clutch could unlock the two IRWs of the DCW in a sharp curve to endue it with the characteristic of an IRW, so that the vehicles can go through the tight curve smoothly. To study the dynamic performance of the DCW, a multi-body dynamic model of single bogie with DCWs was established. The self-centering capability, hunting stability, and self-steering performance on a curved track were analyzed and then compared with those of the conventional wheelset and IRW. Finally, the effect of coupling parameters of the DCW on the dynamic performance was investigated.展开更多
Designing novel lubricants with easily customized structures,devisable compositions,and simple and economic synthesis over traditional lubricants is critical to fulfilling complex applications,prolonging machine lifet...Designing novel lubricants with easily customized structures,devisable compositions,and simple and economic synthesis over traditional lubricants is critical to fulfilling complex applications,prolonging machine lifetime,and saving energy.Deep eutectic solvents(DESs),which show tunable composition,adjustable structure,easy fabrication,and environmental friendliness,are promising candidates for variable and complicated lubricants applications.To promote the use of DESs as lubricants,a series of PEG200-based DESs with active heteroatoms were fabricated to tailor the tribological performance via tribo-chemistry.Thereinto,PEG200/boric acid(BA)DES shows optimal lubrication performance by forming tribo-chemical reaction film composited of B2O3,iron oxides,and FeOOH,and PEG200/thiourea(TU)DES displays abrasive wear-reducing property by producing FeS tribo-chemical film.Given the excellent abrasive wear-resistance of PEG200/TU DES and friction reduction of PEG200/BA DES,ternary PEG200/BA/TU DESs,composited of PEG200/TU DES and PEG200/BA DES,are first exploited.The ternary DESs possess superior wettability and thermal stability,which render them potential lubricants.Tribological tests of the ternary DESs demonstrate that synergistic lubrication is achieved by forming a transfer film consisting of FexBy,BN,B2O3,and FeS.Wherein FexBy,BN,and B2O3 increase load bearing of the film,and FeS mitigates severe abrasive wear.The proposed design philosophy of novel DESs as lubricants opens up a unique realm that is unattainable by traditional DESs lubrication mechanisms and provides a platform to design next-generation DESs lubrication systems.展开更多
By simply switching the electrical circuit installed on steel/steel contact,the tribological behaviors of nanofluids(NFs)can be regulated in real time,thereby achieving the desired performance of friction reduction an...By simply switching the electrical circuit installed on steel/steel contact,the tribological behaviors of nanofluids(NFs)can be regulated in real time,thereby achieving the desired performance of friction reduction and wear resistance.Herein,solvent-free carbon spherical nanofluids(C-NFs)were successfully prepared for intelligent lubrication regulation.C-NFs with excellent lubrication performance can immediately reduce the coefficient of friction(COF)despite applying a weak electric potential(1.5 V).Moreover,polyethylene glycol 400(PEG400)containing 5.0 wt%C-NFs remained responsive to electrical stimulation under the intermittent voltage application with an average coefficient of friction(ACOF)reduction of 20.8%over PEG400.Such intelligent lubrication regulation of C-NFs under an external electric field(EEF)mainly depends on the orderly arranged double-electric adsorption film of ion canopy-adsorbed carbon spheres(CSs).The intermittent electrical application can continuously reinforce the adsorption film and its durability for real-time controlling the sliding interfaces.Electrical-stimulation-responsive intelligent lubricants provide a new technical support for realizing intelligent stepless control of devices.展开更多
The bonded MoS_(2)solid lubricant coating is an effective measure to mitigate the fretting wear of AISI 1045 steel.In this work,the amino functionalized MoS_(2)was protonated with acetic acid to make the MoS_(2)positi...The bonded MoS_(2)solid lubricant coating is an effective measure to mitigate the fretting wear of AISI 1045 steel.In this work,the amino functionalized MoS_(2)was protonated with acetic acid to make the MoS_(2)positively charged.The directional arrangement of protonated MoS2 in the coating was achieved by electrophoretic deposition under the electric field force.The bonded directionally aligned MoS_(2)solid lubricant coating showed high adaptability to various loads and excellent lubrication performance under all three working conditions.At a load of 10 N,the friction coefficient and wear volume of the coating with 5 wt%protonated MoS_(2)decreased by 20.0%and 37.2%compared to the pure epoxy coating,respectively,and by 0.07%and 16.8%than the randomly arranged MoS_(2)sample,respectively.The remarkable lubricating properties of MoS_(2)with directional alignment were attributed to its effective load-bearing and mechanical support,barrier effect on longitudinal extension of cracks,and the formation of a continuous and uniform transfer film.展开更多
Efficient cooperative lubrication can be achieved via the introduction of core‒shell structure lubricant additives with hard core and soft shell,for obtaining the expected anti-wear performance from the structural cha...Efficient cooperative lubrication can be achieved via the introduction of core‒shell structure lubricant additives with hard core and soft shell,for obtaining the expected anti-wear performance from the structural changes in the friction process.In this study,C@Ag microspheres with a core‒shell structure were prepared by the redox method with carbon spheres as the core and Ag nanoparticles as the shell.Their tribological behaviors as base oil(G1830)additive with different concentrations were investigated in detail.Compared with base oil,the addition of C@Ag particles at 0.5 wt%can reduce the coefficient of friction(COF)and wear volume(Wv)up to 15.5%and 88%,respectively.More importantly,C@Ag particles provide superior lubrication performance to single additive(like carbon sphere(CS)and Ag nanoparticle).C@Ag core‒shell particles contribute to the formation of tribo-film by melt bonding of flexible Ag and carbon sphere(CS)toward excellent self-repair performance and high-efficiency lubrication.Hence,core‒shell structural nanoparticles with hard-core and soft-shell hold bright future for high-performance lubrication application.展开更多
Two-dimensional(2D)layered materials,represented by graphene/graphene oxide(GO)and Ti_(3)C_(2)T_(x),are rapidly advancing in their application within anti-corrosion coatings.Their remarkable features,such as large spe...Two-dimensional(2D)layered materials,represented by graphene/graphene oxide(GO)and Ti_(3)C_(2)T_(x),are rapidly advancing in their application within anti-corrosion coatings.Their remarkable features,such as large specific surface area,adjustable structure and functionality,and diverse arrangement forms,endow them with vast potential as anticorrosion materials.This paper,anchored in the highly oriented arrangement of 2D materials in coatings,provides an overview of the anti-corrosion potential of composite materials with ordered microstructures.It explores the dispersion and orientation of 2D materials in resin coating matrices under force field induction,electric field induction,and magnetic field induction.Additionally,it offers a detailed introduction to recent advances in the self-aligned arrangement of graphene/graphene oxide and Ti_(3)C_(2)T_(x)in resin coatings,focusing on their anti-corrosion applications and underlying mechanisms.Finally,the paper summarizes and anticipates the future prospects of directional distribution of 2D materials in the anti-corrosion field,aiming to provide new insights into the interface construction and performance regulation of these materials,and to inspire the development of high-performance anti-corrosion coatings with simple preparation processes and exceptional protective properties.展开更多
Two-dimensional Ti_(3)C_(2)T_(x) flakes have great application potential in various areas due to their optical,electronic,electrochemical and mechanical properties,but their anti-corrosion and wear-resistance performa...Two-dimensional Ti_(3)C_(2)T_(x) flakes have great application potential in various areas due to their optical,electronic,electrochemical and mechanical properties,but their anti-corrosion and wear-resistance performance were not well understood.The difficulties in achieving good dispersity and interface interaction of inorganic additives in organic coatings hinder the incorporation of Ti_(3)C_(2)T_(x) into the epoxy coating.Here,few-layered Ti_(3)C_(2)T_(x) sheets with amino-functionalization were prepared,and as reinforced-additives were added into the waterborne epoxy coating.Anti-corrosion and tribological properties of as-prepared composite coatings were investigated in detail.The results reveal that the composite coating with 0.5 wt.%amino-functionalized Ti_(3)C_(2)T_(x) sheets shows excellent corrosion protection(the lowest frequency impedance was 3.12×10^(9) cm^(2))and wear resistance(wear rate was reduced by 72.74%).The greatly improving performance of composite coatings mainly depends on:(a)good dispersity and compatibility of amino-functionalized Ti_(3)C_(2)T_(x) in organic matrix,(b)high adhesion strength between coating and metal substrate and(c)the intrinsic properties of Ti3C2Tx sheets.The work provides a good path for applications of MXene as multifunctional additives.展开更多
This paper investigates the self-loosening of threaded fasteners subjected to dynamic shear load. Three kinds of typical coatings, PTFE, MoS_2, and TiN applied to bolts and nuts, are tested in this investigation. The ...This paper investigates the self-loosening of threaded fasteners subjected to dynamic shear load. Three kinds of typical coatings, PTFE, MoS_2, and TiN applied to bolts and nuts, are tested in this investigation. The study experimentally examines the loosening mechanisms of fasteners and assesses the anti-loosening performance of the three tested coatings based on their tightening characteristics, loosening curves, and the damage of thread surface. Additionally, the anti-loosening performance of the three coatings is compared under different load forms. The results indicate that the PTFE and MoS_2 coatings have significant anti-loosening effect, whereas the anti-loosening performance of Ti N coating is not satisfactory. It is also found that an appropriate increase of the initial tightening torque can significantly improve the anti-loosening effect. In addition, the microscopic analyses of PTFE and MoS2 coating reveal that a reduced initial tightening torque leads to fretting wear on the thread contact surfaces of fasteners, thereby aggravating the damage.展开更多
Surface and interface engineering plays a crucial role in modulating the properties of materials,especially two-dimensional(2D)materials.Hence,a strategy,forming heterostructures with MoS_(2),is proposed to overcome t...Surface and interface engineering plays a crucial role in modulating the properties of materials,especially two-dimensional(2D)materials.Hence,a strategy,forming heterostructures with MoS_(2),is proposed to overcome the natural agglomeration of Ti_(3)C_(2)T_(x) MXene nanosheets.Most importantly,the interactions between Ti_(3)C_(2)Tx and MoS_(2) were elaborately investigated by first-principles calculations based on density functional theory(DFT)for the first time.The calculations demonstrate that van der Waals forces dominate the interface interactions of Ti_(3)C_(2)T_(x) and MoS_(2),rendering Ti_(3)C_(2)T_(x)@MoS_(2) heterostructures favorable stability.The Ti_(3)C_(2)T_(x)@MoS_(2) heterostructure composites were synthesized through a facile one-step hydrothermal method and exhibit a 2D hierarchical structure.Furthermore,the corrosion and tribological properties of epoxy composite coatings with varying proportions of Ti_(3)C_(2)T_(x)@MoS_(2) composites were studied in detail.As a result,the epoxy composite coating with 0.1 wt.%Ti_(3)C_(2)T_(x)@MoS_(2) composites(Ti_(3)C_(2)T_(x)@MoS_(2)-0.1)exhibits excellent corrosion protection and antiwear performances.The Ti_(3)C_(2)T_(x)@MoS_(2)-0.1 keeps the largest low-frequency impedance modulus(|Z|_(0.)01 Hz)and coating resistance(R_(c))during the whole immersion period.Its wear rate is 0.09μm^(3)/(Nμm)under the load of 10 N,one half of that of pure epoxy coating(EP).This work further broadens the application of MXene-based heterostructure composites.展开更多
Thickener formulation plays a significant role in the performance characteristics of grease.The polyurea greases(PUGs)were synthesized using mineral oil(500SN)as the base oil,and by regulating the reaction of diphenyl...Thickener formulation plays a significant role in the performance characteristics of grease.The polyurea greases(PUGs)were synthesized using mineral oil(500SN)as the base oil,and by regulating the reaction of diphenylmethane diisocyanate(MDI)and different organic amines.The as‐prepared PUGs from the reaction of MDI and cyclohexylamine/p‐toluidine exhibit the optimum physicochemical and friction‐wear properties,confirming that the regulation of thickener formulation can improve the performance characteristics of grease,including friction reduction,wear,corrosion resistance,and load‐carrying capacity.The anticorrosion and lubrication properties of as‐prepared PUGs depend on good sealing functions and a boundary lubrication film(synergy of grease‐film and tribo‐chemical reaction film),as well as their chemical components and structure.展开更多
The operational safety and reliability of a variable gauge train are affected by the anti-fretting wear performance of the locking mechanism.The main purpose of this study is to optimize the surface treatment process ...The operational safety and reliability of a variable gauge train are affected by the anti-fretting wear performance of the locking mechanism.The main purpose of this study is to optimize the surface treatment process for a locking pin material under actual service conditions to alleviate fretting damage.Based on the two basic principles of surface strengthening and friction reduction,a substrate(AISI 4135 steel)surface was treated by laser quenching(LQ),plasma nitriding(PN),and bonded MoS2 coating.Systematic fretting wear tests were conducted,and the wear behavior and damage mechanism of various treated surfaces were comprehensively investigated.The results indicate that the wear resistances of the LQ-and PN-treated surfaces were significantly improved,and their main wear mechanisms were abrasive wear,delamination,and oxidation wear.The MoS_(2) coating exhibits the lowest friction coefficient and energy dissipation due to its self-lubricating property,but it incurs the highest wear rate and failure in the form of plastic deformation.Furthermore,the rough compound layer with a high hardness on the PN-treated surface is conducive to the formation and maintenance of the third-body contact at the fretting interface,consequently resulting in a significant reduction in wear.An optimal surface treatment process for alleviating fretting damage of the locking pin is recommended via comprehensive evaluation,which provides a reference for the anti-fretting protection of related mechanical components.展开更多
In this study,lithium complex grease(LCG)and polyurea grease(PUG)were synthesized using mineral oil(500 SN)and polyalphaolefin(PAO40)as base oil,adsorbed onto lithium complex soap and polyurea as thickeners,respective...In this study,lithium complex grease(LCG)and polyurea grease(PUG)were synthesized using mineral oil(500 SN)and polyalphaolefin(PAO40)as base oil,adsorbed onto lithium complex soap and polyurea as thickeners,respectively.The effects of grease formulation(thickener and base oil with different amounts(80,85,and 90 wt%)on the corrosion resistance and lubrication function were investigated in detail.The results have verified that the as-prepared greases have good anti-corrosion ability,ascribed to good salt-spray resistance and sealing function.Furthermore,the increase in the amount of base oil reduces the friction of the contact interface to some extent,whereas the wear resistance of these greases is not consistent with the friction reduction,because the thickener has a significant influence on the tribological property of greases,especially load-carrying capacity.PUG displays better physicochemical performance and lubrication function than LCG under the same conditions,mainly depending on the component/structure of polyurea thickener.The polyurea grease with 90 wt%PAO displays the best wear resistance owing to the synergistic lubrication of grease-film and tribochemical film,composed of Fe_(2)O_(3),FeO(OH),and nitrogen oxide.展开更多
The few-layer Ti_(3)C_(2)T_(x)/MoS_(2) heterostructure was successfully prepared via vertically growing of MoS_(2) nanosheets on the few-layer Ti3C2Tx matrix using hydrothermal method.The tribological properties as ad...The few-layer Ti_(3)C_(2)T_(x)/MoS_(2) heterostructure was successfully prepared via vertically growing of MoS_(2) nanosheets on the few-layer Ti3C2Tx matrix using hydrothermal method.The tribological properties as additive in mineral oil(150N)were evaluated in detail.The 0.3 wt% of few-layer Ti_(3)C_(2)T_(x)/MoS_(2) heterostructure addition amount can reduce the friction and wear of 150N by 39% and 85%,respectively.Moreover,the enhancement effect of few-layer Ti_(3)C_(2)T_(x)/MoS_(2) on tribological properties of 150N is superior to that of few-layer Ti_(3)C_(2)T_(x),MoS_(2) nanosheets,and their mechanical mixture.Based on the characterization and analysis of wear debris and wear track,such excellent tribological properties of the few-layer Ti_(3)C_(2)T_(x)/MoS_(2) heterostructure derive from its structural advantage toward good dispersion,the synergistic lubrication of Ti_(3)C_(2)T_(x) and MoS_(2) nanosheets during the rubbing process,and the formation of tribo-film.展开更多
In many industrial devices, impact-sliding wear is caused by a variety of complex vibrations between the contacted interfaces. Under actual conditions, impact and sliding motions do not occur in only one direction, an...In many industrial devices, impact-sliding wear is caused by a variety of complex vibrations between the contacted interfaces. Under actual conditions, impact and sliding motions do not occur in only one direction, and different complex impact-sliding motions exist on the tribology surfaces. In this study, an impact-sliding wear test rig is developed to investigate the wear effect of different complex motions. Using this rig, multi-type impact-sliding wear effects are realized and measured, such as those derived from unidirectional, reciprocating, and multi-mode combination motions. These three types of impact–sliding wear running behavior are tested and the wear damage mechanism is discussed.展开更多
Tribological property of c-axis textured shell-like Ti3AlC2 ceramic was investigated using reciprocating sliding balls (SUS304) under loads of 1,5,and 9 N.It was found that the textured top surface (TTS),corresponding...Tribological property of c-axis textured shell-like Ti3AlC2 ceramic was investigated using reciprocating sliding balls (SUS304) under loads of 1,5,and 9 N.It was found that the textured top surface (TTS),corresponding to the (000l) plane,shows the lowest mean coefficient of friction in comparison with those measured on the textured side surface (TSS),where the sliding directions are parallel (TSS-1) and perpendicular (TSS-2) to c axis,under the same load.Among all the tested orientations,the TSS-2 exhibited the lowest wear rate of 1.51 × 10-3 mm3/(N·m) under the load of 9 N.The worn mechanisms on the TTS and TSS-1 were delamination,grain fracture,and grain spalling-off.On the TSS-2,plowing effect against balls was the dominating mechanism.This work suggests the criteria to maximize the wear resistance in the load range of 1-9 N.展开更多
Deep eutectic solvents(DESs)have been considered as novel and economic alternatives to traditional lubricants because of their similar physicochemical performance.In this study,choline chloride(ChCl)DESs were successf...Deep eutectic solvents(DESs)have been considered as novel and economic alternatives to traditional lubricants because of their similar physicochemical performance.In this study,choline chloride(ChCl)DESs were successfully synthesized via hydrogen-bonding networks of urea and thiourea as the hydrogen bond donors(HBDs).The as-synthesized ChCl-urea and ChCl-thiourea DESs had excellent thermal stability and displayed good lubrication between steel/steel tribo-pairs.The friction coefficient and wear rate of ChCl-thiourea DES were 50.1%and 80.6%,respectively,lower than those of ChCl-urea DES for GCr15/45 steel tribo-pairs.However,for GCr15/Q45 steel,ChCl-urea DES decreased the wear rate by 85.0%in comparison to ChCl-thiourea DES.Under ChCl-thiourea DES lubrication,the tribo-chemical reaction film composed of FeS formed at the interfaces and contributed to low friction and wear.However,under high von Mises stress,the film could not be stably retained and serious wear was obtained through direct contact of friction pairs.This illustrated that the evolution of the tribo-chemical reaction film was responsible for the anti-friction and anti-wearproperties of the DESs.展开更多
The impact-sliding wear behavior of steam generator tubes in nuclear power plants is complex owing to the dynamic nature of the mechanical response and self-induced tribological changes.In this study,the effects of im...The impact-sliding wear behavior of steam generator tubes in nuclear power plants is complex owing to the dynamic nature of the mechanical response and self-induced tribological changes.In this study,the effects of impact and sliding velocity on the impact-sliding wear behavior of a 2.25Cr1Mo steel tube are investigated experimentally and numerically.In the experimental study,a wear test rig that can measure changes in the impact and friction forces as well as the compressive displacement over different wear cycles,both in real time,is designed.A semi-analytical model based on the Archard wear law and Hertz contact theory is used to predict wear.The results indicate that the impact dynamic effect by the impact velocity is more significant than that of the sliding velocity,and that both velocities affect the friction force and wear degree.The experimental results for the wear depth evolution agree well with the corresponding simulation predictions.展开更多
Deformation twin is one of the most important strain accommodation mechanisms and ultimately influences the mechanical properties for magnesium and its alloys.Especially,{1011}twin is usually thought to be closely rel...Deformation twin is one of the most important strain accommodation mechanisms and ultimately influences the mechanical properties for magnesium and its alloys.Especially,{1011}twin is usually thought to be closely related to the fracture or fatigue process of magnesium alloys.In the present work,the characteristics of microstructure near fracture region of deformed magnesium alloy have been investigated by a combination of electron back-scatter diffraction(EBSD)and transmission electron microscope(TEM).It has found that a large of deformation twins occur near fraction region,including{1012}and{1011}primary twins,{1011}-{1012}double twin and{1011}-{1012}-{1011}-{1012}quadruple twin.The actual boundaries of{1011}twins at atomic scale consist of{1011}coherent twinning boundaries(TBs)and parallel basal-pyramidal(BPy/Py B)planes.The tip of{1011}twin can even end up with BPy/Py B interfaces only.The experimental observations also reveal that when two{1011}twin variants sharing a common[1120]zone axis approach each other,the growth of one twin is usually hindered by the boundaries of the other twin.In addition,an apparent"crossing"phenomenon is also discovered when interaction of two{1011}twins takes place.According to these experimental observations,the possible underlying mechanisms behind such phenomena are proposed and discussed.These finding are expected to provide an insight into understanding the twinning behavior and the relationship between twin and fracture in magnesium and other materials with hexagonal structure.展开更多
In this study,spherical and mesoporous NiAl particles(abbreviated as sNiAl and mNiAl)were introduced as lubricant additives into two alkyl-imidazolium ionic liquids(ILs)(l-butyl-3-methylimidazolium tetrafluoroborate(L...In this study,spherical and mesoporous NiAl particles(abbreviated as sNiAl and mNiAl)were introduced as lubricant additives into two alkyl-imidazolium ionic liquids(ILs)(l-butyl-3-methylimidazolium tetrafluoroborate(LB104)and l-butyl-3-methyl imidazolium hexafluorophosphate(LP104))to explore their tribological properties.The sNiAl and mNiAl particles were modified in-situ by anion and cation moieties of ILs through chemical interaction,thereby enhancing their dispersibility and stability in ILs.The mNiAl particles have better dispersibility than the sNiAl ones in ILs because of high specific surface area.LP104-modified sNiAl particles show better friction reduction and wear resistance,mainly relying on the synergy of the hybrid lubricant.These particles form a protective layer that prevents friction pairs from straight asperity contact and improves the tribological behaviors.展开更多
基金Supported by National Natural Science Foundation of China(Grant Nos.52075458 and U2141211).
文摘Graphene as a lubricating additive holds great potential for industrial lubrication. However, its poor dispersity and compatibility with base oils and grease hinder maximizing performance. Here, the infuence of graphene dispersion on the thickening efect and lubrication function is considered. A well-dispersed lubricant additive was obtained via trihexyl tetradecyl phosphonium bis(2-ethylhexyl) phosphate modifed graphene ([P_(66614)][DEHP]-G). Then lithium complex grease was prepared by saponifcation with 12-OH stearic acid, sebacic acid, and lithium hydroxide, using polyalphaolefn (PAO20) as base oil and the modifed-graphene as lubricating additive, with the original graphene as a comparison. The physicochemical properties and lubrication performance of the as-prepared greases were evaluated in detail. The results show that the as-prepared greases have high dropping point and colloidal stability. Furthermore, modifed-graphene lithium complex grease ofered the best friction reduction and anti-wear abilities, manifesting the reduction of friction coefcient and wear volume up to 18.84% and 67.34%, respectively. With base oil overfow and afux, well-dispersed [P_(66614)][DEHP]-G was readily adsorbed to the worn surfaces, resulting in the formation of a continuous and dense graphene deposition flm. The synergy of deposited graphene-flm, spilled oil, and adhesive grease greatly improves the lubrication function of grease. This research paves the way for modulating high-performance lithium complex grease to reduce the friction and wear of movable machinery.
基金supported by the National Key Technology R&D Program of China (No. 2009BAG12A02)the National Basic Research Program of China (No. 2011CB711106)+2 种基金the Program for Innovative Research Team in University (No. IRT1178)the Program for New Century Excellent Talents in University (No. NCET-10-0664)the National Key Technology R&D Program (No. 2009BAG12A01)
文摘In order to improve the curving performance of the conventional wheelset in sharp curves and resolve the steering ability problem of the independently rotating wheel in large radius curves and tangent lines, a differential cou- pling wheelset （DCW） was developed in this work. The DCW was composed of two independently rotating wheels （IRWs） coupled by a clutch-type limited slip differential. The differential contains a static pre-stress clutch, which could lock both sides of IRWs of the DCW to ensure a good steering performance in curves with large radius and tangent track. In contrast, the clutch could unlock the two IRWs of the DCW in a sharp curve to endue it with the characteristic of an IRW, so that the vehicles can go through the tight curve smoothly. To study the dynamic performance of the DCW, a multi-body dynamic model of single bogie with DCWs was established. The self-centering capability, hunting stability, and self-steering performance on a curved track were analyzed and then compared with those of the conventional wheelset and IRW. Finally, the effect of coupling parameters of the DCW on the dynamic performance was investigated.
基金support from the National Natural Science Foundation of China(Nos.52175190 and 51805455)and the Fundamental Research Funds for the Central Universities(No.2682021CX117).
文摘Designing novel lubricants with easily customized structures,devisable compositions,and simple and economic synthesis over traditional lubricants is critical to fulfilling complex applications,prolonging machine lifetime,and saving energy.Deep eutectic solvents(DESs),which show tunable composition,adjustable structure,easy fabrication,and environmental friendliness,are promising candidates for variable and complicated lubricants applications.To promote the use of DESs as lubricants,a series of PEG200-based DESs with active heteroatoms were fabricated to tailor the tribological performance via tribo-chemistry.Thereinto,PEG200/boric acid(BA)DES shows optimal lubrication performance by forming tribo-chemical reaction film composited of B2O3,iron oxides,and FeOOH,and PEG200/thiourea(TU)DES displays abrasive wear-reducing property by producing FeS tribo-chemical film.Given the excellent abrasive wear-resistance of PEG200/TU DES and friction reduction of PEG200/BA DES,ternary PEG200/BA/TU DESs,composited of PEG200/TU DES and PEG200/BA DES,are first exploited.The ternary DESs possess superior wettability and thermal stability,which render them potential lubricants.Tribological tests of the ternary DESs demonstrate that synergistic lubrication is achieved by forming a transfer film consisting of FexBy,BN,B2O3,and FeS.Wherein FexBy,BN,and B2O3 increase load bearing of the film,and FeS mitigates severe abrasive wear.The proposed design philosophy of novel DESs as lubricants opens up a unique realm that is unattainable by traditional DESs lubrication mechanisms and provides a platform to design next-generation DESs lubrication systems.
基金gratefully acknowledged the financial support provided by the National Natural Science Foundation of China(Nos.52075458 and U2141211)Meanwhile,the authors gratefully acknowledged University-Industry Collaborative Education Program,Fundamental Research Funds for the Central Universities(No.2682021CG008)Analysis&Testing Center of Southwest Jiaotong University,China,for supporting the SEM measurements.
文摘By simply switching the electrical circuit installed on steel/steel contact,the tribological behaviors of nanofluids(NFs)can be regulated in real time,thereby achieving the desired performance of friction reduction and wear resistance.Herein,solvent-free carbon spherical nanofluids(C-NFs)were successfully prepared for intelligent lubrication regulation.C-NFs with excellent lubrication performance can immediately reduce the coefficient of friction(COF)despite applying a weak electric potential(1.5 V).Moreover,polyethylene glycol 400(PEG400)containing 5.0 wt%C-NFs remained responsive to electrical stimulation under the intermittent voltage application with an average coefficient of friction(ACOF)reduction of 20.8%over PEG400.Such intelligent lubrication regulation of C-NFs under an external electric field(EEF)mainly depends on the orderly arranged double-electric adsorption film of ion canopy-adsorbed carbon spheres(CSs).The intermittent electrical application can continuously reinforce the adsorption film and its durability for real-time controlling the sliding interfaces.Electrical-stimulation-responsive intelligent lubricants provide a new technical support for realizing intelligent stepless control of devices.
基金the financial support of National Natural Science Foundation of China(Nos.52075458 and U2141211)Sichuan Science Foundation for Distinguished Young Scholars(No.2023NSFSC1957)the Analytical and Testing Center of Southwest Jiaotong University for support of the scanning electron microscopy(SEM)and Raman measurements.
文摘The bonded MoS_(2)solid lubricant coating is an effective measure to mitigate the fretting wear of AISI 1045 steel.In this work,the amino functionalized MoS_(2)was protonated with acetic acid to make the MoS_(2)positively charged.The directional arrangement of protonated MoS2 in the coating was achieved by electrophoretic deposition under the electric field force.The bonded directionally aligned MoS_(2)solid lubricant coating showed high adaptability to various loads and excellent lubrication performance under all three working conditions.At a load of 10 N,the friction coefficient and wear volume of the coating with 5 wt%protonated MoS_(2)decreased by 20.0%and 37.2%compared to the pure epoxy coating,respectively,and by 0.07%and 16.8%than the randomly arranged MoS_(2)sample,respectively.The remarkable lubricating properties of MoS_(2)with directional alignment were attributed to its effective load-bearing and mechanical support,barrier effect on longitudinal extension of cracks,and the formation of a continuous and uniform transfer film.
基金the National Natural Science Foundation of China(Nos.52075458 and U2141211)the Sichuan Science Foundation for Distinguished Young Scholars(No.2023NSFSC1957)。
文摘Efficient cooperative lubrication can be achieved via the introduction of core‒shell structure lubricant additives with hard core and soft shell,for obtaining the expected anti-wear performance from the structural changes in the friction process.In this study,C@Ag microspheres with a core‒shell structure were prepared by the redox method with carbon spheres as the core and Ag nanoparticles as the shell.Their tribological behaviors as base oil(G1830)additive with different concentrations were investigated in detail.Compared with base oil,the addition of C@Ag particles at 0.5 wt%can reduce the coefficient of friction(COF)and wear volume(Wv)up to 15.5%and 88%,respectively.More importantly,C@Ag particles provide superior lubrication performance to single additive(like carbon sphere(CS)and Ag nanoparticle).C@Ag core‒shell particles contribute to the formation of tribo-film by melt bonding of flexible Ag and carbon sphere(CS)toward excellent self-repair performance and high-efficiency lubrication.Hence,core‒shell structural nanoparticles with hard-core and soft-shell hold bright future for high-performance lubrication application.
基金financial support provided by National Natural Science Foundation of China(U2141211,52201095)Sichuan Science Foundation for Distinguished Young Scholars(2023NSFSC1957)Fundamental Research Funds for the Central Universities(2682024GF006).
文摘Two-dimensional(2D)layered materials,represented by graphene/graphene oxide(GO)and Ti_(3)C_(2)T_(x),are rapidly advancing in their application within anti-corrosion coatings.Their remarkable features,such as large specific surface area,adjustable structure and functionality,and diverse arrangement forms,endow them with vast potential as anticorrosion materials.This paper,anchored in the highly oriented arrangement of 2D materials in coatings,provides an overview of the anti-corrosion potential of composite materials with ordered microstructures.It explores the dispersion and orientation of 2D materials in resin coating matrices under force field induction,electric field induction,and magnetic field induction.Additionally,it offers a detailed introduction to recent advances in the self-aligned arrangement of graphene/graphene oxide and Ti_(3)C_(2)T_(x)in resin coatings,focusing on their anti-corrosion applications and underlying mechanisms.Finally,the paper summarizes and anticipates the future prospects of directional distribution of 2D materials in the anti-corrosion field,aiming to provide new insights into the interface construction and performance regulation of these materials,and to inspire the development of high-performance anti-corrosion coatings with simple preparation processes and exceptional protective properties.
基金the National Natural Science Foundation of China(Nos.51705435 and 51575459)the Key Project of Sichuan Department of Science and Technology(Nos.2018JZ0048 and 2019YFG0292)。
文摘Two-dimensional Ti_(3)C_(2)T_(x) flakes have great application potential in various areas due to their optical,electronic,electrochemical and mechanical properties,but their anti-corrosion and wear-resistance performance were not well understood.The difficulties in achieving good dispersity and interface interaction of inorganic additives in organic coatings hinder the incorporation of Ti_(3)C_(2)T_(x) into the epoxy coating.Here,few-layered Ti_(3)C_(2)T_(x) sheets with amino-functionalization were prepared,and as reinforced-additives were added into the waterborne epoxy coating.Anti-corrosion and tribological properties of as-prepared composite coatings were investigated in detail.The results reveal that the composite coating with 0.5 wt.%amino-functionalized Ti_(3)C_(2)T_(x) sheets shows excellent corrosion protection(the lowest frequency impedance was 3.12×10^(9) cm^(2))and wear resistance(wear rate was reduced by 72.74%).The greatly improving performance of composite coatings mainly depends on:(a)good dispersity and compatibility of amino-functionalized Ti_(3)C_(2)T_(x) in organic matrix,(b)high adhesion strength between coating and metal substrate and(c)the intrinsic properties of Ti3C2Tx sheets.The work provides a good path for applications of MXene as multifunctional additives.
基金the financial support provided by the National Science Funds for Distinguished Young Scholars(No.51025519)the Changjiang Scholarships and Innovation Team Development Plan(No.IRT1178)the Self-Topic Fund of Traction Power State Key Laboratory(No.2016TPL-Z03)
文摘This paper investigates the self-loosening of threaded fasteners subjected to dynamic shear load. Three kinds of typical coatings, PTFE, MoS_2, and TiN applied to bolts and nuts, are tested in this investigation. The study experimentally examines the loosening mechanisms of fasteners and assesses the anti-loosening performance of the three tested coatings based on their tightening characteristics, loosening curves, and the damage of thread surface. Additionally, the anti-loosening performance of the three coatings is compared under different load forms. The results indicate that the PTFE and MoS_2 coatings have significant anti-loosening effect, whereas the anti-loosening performance of Ti N coating is not satisfactory. It is also found that an appropriate increase of the initial tightening torque can significantly improve the anti-loosening effect. In addition, the microscopic analyses of PTFE and MoS2 coating reveal that a reduced initial tightening torque leads to fretting wear on the thread contact surfaces of fasteners, thereby aggravating the damage.
基金financially supported by the National Natural Science Foundation of China(No.52075458)the Sichuan Science and Technology Program(No.2021JDRC0094)。
文摘Surface and interface engineering plays a crucial role in modulating the properties of materials,especially two-dimensional(2D)materials.Hence,a strategy,forming heterostructures with MoS_(2),is proposed to overcome the natural agglomeration of Ti_(3)C_(2)T_(x) MXene nanosheets.Most importantly,the interactions between Ti_(3)C_(2)Tx and MoS_(2) were elaborately investigated by first-principles calculations based on density functional theory(DFT)for the first time.The calculations demonstrate that van der Waals forces dominate the interface interactions of Ti_(3)C_(2)T_(x) and MoS_(2),rendering Ti_(3)C_(2)T_(x)@MoS_(2) heterostructures favorable stability.The Ti_(3)C_(2)T_(x)@MoS_(2) heterostructure composites were synthesized through a facile one-step hydrothermal method and exhibit a 2D hierarchical structure.Furthermore,the corrosion and tribological properties of epoxy composite coatings with varying proportions of Ti_(3)C_(2)T_(x)@MoS_(2) composites were studied in detail.As a result,the epoxy composite coating with 0.1 wt.%Ti_(3)C_(2)T_(x)@MoS_(2) composites(Ti_(3)C_(2)T_(x)@MoS_(2)-0.1)exhibits excellent corrosion protection and antiwear performances.The Ti_(3)C_(2)T_(x)@MoS_(2)-0.1 keeps the largest low-frequency impedance modulus(|Z|_(0.)01 Hz)and coating resistance(R_(c))during the whole immersion period.Its wear rate is 0.09μm^(3)/(Nμm)under the load of 10 N,one half of that of pure epoxy coating(EP).This work further broadens the application of MXene-based heterostructure composites.
文摘Thickener formulation plays a significant role in the performance characteristics of grease.The polyurea greases(PUGs)were synthesized using mineral oil(500SN)as the base oil,and by regulating the reaction of diphenylmethane diisocyanate(MDI)and different organic amines.The as‐prepared PUGs from the reaction of MDI and cyclohexylamine/p‐toluidine exhibit the optimum physicochemical and friction‐wear properties,confirming that the regulation of thickener formulation can improve the performance characteristics of grease,including friction reduction,wear,corrosion resistance,and load‐carrying capacity.The anticorrosion and lubrication properties of as‐prepared PUGs depend on good sealing functions and a boundary lubrication film(synergy of grease‐film and tribo‐chemical reaction film),as well as their chemical components and structure.
基金This work was supported by the National Natural Science Foundation of China(Grant No.51627806).
文摘The operational safety and reliability of a variable gauge train are affected by the anti-fretting wear performance of the locking mechanism.The main purpose of this study is to optimize the surface treatment process for a locking pin material under actual service conditions to alleviate fretting damage.Based on the two basic principles of surface strengthening and friction reduction,a substrate(AISI 4135 steel)surface was treated by laser quenching(LQ),plasma nitriding(PN),and bonded MoS2 coating.Systematic fretting wear tests were conducted,and the wear behavior and damage mechanism of various treated surfaces were comprehensively investigated.The results indicate that the wear resistances of the LQ-and PN-treated surfaces were significantly improved,and their main wear mechanisms were abrasive wear,delamination,and oxidation wear.The MoS_(2) coating exhibits the lowest friction coefficient and energy dissipation due to its self-lubricating property,but it incurs the highest wear rate and failure in the form of plastic deformation.Furthermore,the rough compound layer with a high hardness on the PN-treated surface is conducive to the formation and maintenance of the third-body contact at the fretting interface,consequently resulting in a significant reduction in wear.An optimal surface treatment process for alleviating fretting damage of the locking pin is recommended via comprehensive evaluation,which provides a reference for the anti-fretting protection of related mechanical components.
基金the financial support provided by the National Natural Science Foundation of China(No.51705435)Fundamental Research Funds for the Central Universities(2018GF05)Key Laboratory of Material Corrosion and Protection of Sichuan(2018CL14)。
文摘In this study,lithium complex grease(LCG)and polyurea grease(PUG)were synthesized using mineral oil(500 SN)and polyalphaolefin(PAO40)as base oil,adsorbed onto lithium complex soap and polyurea as thickeners,respectively.The effects of grease formulation(thickener and base oil with different amounts(80,85,and 90 wt%)on the corrosion resistance and lubrication function were investigated in detail.The results have verified that the as-prepared greases have good anti-corrosion ability,ascribed to good salt-spray resistance and sealing function.Furthermore,the increase in the amount of base oil reduces the friction of the contact interface to some extent,whereas the wear resistance of these greases is not consistent with the friction reduction,because the thickener has a significant influence on the tribological property of greases,especially load-carrying capacity.PUG displays better physicochemical performance and lubrication function than LCG under the same conditions,mainly depending on the component/structure of polyurea thickener.The polyurea grease with 90 wt%PAO displays the best wear resistance owing to the synergistic lubrication of grease-film and tribochemical film,composed of Fe_(2)O_(3),FeO(OH),and nitrogen oxide.
基金The authors gratefully acknowledge the financial support provided by National Natural Science Foundation of China(No.52075458)Sichuan Science and Technology Program(No.2021JDRC0094).
文摘The few-layer Ti_(3)C_(2)T_(x)/MoS_(2) heterostructure was successfully prepared via vertically growing of MoS_(2) nanosheets on the few-layer Ti3C2Tx matrix using hydrothermal method.The tribological properties as additive in mineral oil(150N)were evaluated in detail.The 0.3 wt% of few-layer Ti_(3)C_(2)T_(x)/MoS_(2) heterostructure addition amount can reduce the friction and wear of 150N by 39% and 85%,respectively.Moreover,the enhancement effect of few-layer Ti_(3)C_(2)T_(x)/MoS_(2) on tribological properties of 150N is superior to that of few-layer Ti_(3)C_(2)T_(x),MoS_(2) nanosheets,and their mechanical mixture.Based on the characterization and analysis of wear debris and wear track,such excellent tribological properties of the few-layer Ti_(3)C_(2)T_(x)/MoS_(2) heterostructure derive from its structural advantage toward good dispersion,the synergistic lubrication of Ti_(3)C_(2)T_(x) and MoS_(2) nanosheets during the rubbing process,and the formation of tribo-film.
基金supported by the National Natural Science Foundation of China (Nos.51375407,U1530136,and 51627806)the Young Scientific Innovation Team of Science and Technology of Sichuan (No.2017TD0017)
文摘In many industrial devices, impact-sliding wear is caused by a variety of complex vibrations between the contacted interfaces. Under actual conditions, impact and sliding motions do not occur in only one direction, and different complex impact-sliding motions exist on the tribology surfaces. In this study, an impact-sliding wear test rig is developed to investigate the wear effect of different complex motions. Using this rig, multi-type impact-sliding wear effects are realized and measured, such as those derived from unidirectional, reciprocating, and multi-mode combination motions. These three types of impact–sliding wear running behavior are tested and the wear damage mechanism is discussed.
基金'ChuYing' Program of Southwest Jiaotong University and Thousand Talents Program of Sichuan Province.Also,we thank for the supports of National Natural Science Foundation of China，Grant-in-Aid for Scientific Research B (No.23350104) from Japan Society for the Promotion Science,the Fundamental Research Program of Korean Institute of Materials Science，UK EPSRC Material Systems for Extreme Environments Programme Grant
文摘Tribological property of c-axis textured shell-like Ti3AlC2 ceramic was investigated using reciprocating sliding balls (SUS304) under loads of 1,5,and 9 N.It was found that the textured top surface (TTS),corresponding to the (000l) plane,shows the lowest mean coefficient of friction in comparison with those measured on the textured side surface (TSS),where the sliding directions are parallel (TSS-1) and perpendicular (TSS-2) to c axis,under the same load.Among all the tested orientations,the TSS-2 exhibited the lowest wear rate of 1.51 × 10-3 mm3/(N·m) under the load of 9 N.The worn mechanisms on the TTS and TSS-1 were delamination,grain fracture,and grain spalling-off.On the TSS-2,plowing effect against balls was the dominating mechanism.This work suggests the criteria to maximize the wear resistance in the load range of 1-9 N.
基金The authors acknowledge the supports from the National Natural Science Foundation of China(No.51805455)Sichuan Science and Technology Program(Nos.2019YFG0306 and 2019YFSY0012)the Fundamental Research Funds for the Central Universities(No.2682020CX04).
文摘Deep eutectic solvents(DESs)have been considered as novel and economic alternatives to traditional lubricants because of their similar physicochemical performance.In this study,choline chloride(ChCl)DESs were successfully synthesized via hydrogen-bonding networks of urea and thiourea as the hydrogen bond donors(HBDs).The as-synthesized ChCl-urea and ChCl-thiourea DESs had excellent thermal stability and displayed good lubrication between steel/steel tribo-pairs.The friction coefficient and wear rate of ChCl-thiourea DES were 50.1%and 80.6%,respectively,lower than those of ChCl-urea DES for GCr15/45 steel tribo-pairs.However,for GCr15/Q45 steel,ChCl-urea DES decreased the wear rate by 85.0%in comparison to ChCl-thiourea DES.Under ChCl-thiourea DES lubrication,the tribo-chemical reaction film composed of FeS formed at the interfaces and contributed to low friction and wear.However,under high von Mises stress,the film could not be stably retained and serious wear was obtained through direct contact of friction pairs.This illustrated that the evolution of the tribo-chemical reaction film was responsible for the anti-friction and anti-wearproperties of the DESs.
基金This study is supported by the National Natural Science Foundation of China(No.U1530136)Young Scientific Innovation Team of Science and Technology of Sichuan(No.2017TD0017)The author Meigui YIN acknowledges the financial support from the China Scholarship Council(CSC No.201907000021).
文摘The impact-sliding wear behavior of steam generator tubes in nuclear power plants is complex owing to the dynamic nature of the mechanical response and self-induced tribological changes.In this study,the effects of impact and sliding velocity on the impact-sliding wear behavior of a 2.25Cr1Mo steel tube are investigated experimentally and numerically.In the experimental study,a wear test rig that can measure changes in the impact and friction forces as well as the compressive displacement over different wear cycles,both in real time,is designed.A semi-analytical model based on the Archard wear law and Hertz contact theory is used to predict wear.The results indicate that the impact dynamic effect by the impact velocity is more significant than that of the sliding velocity,and that both velocities affect the friction force and wear degree.The experimental results for the wear depth evolution agree well with the corresponding simulation predictions.
基金supported financially by National Natural Science Foundation of China(Nos.51801165 and 51575459)the Natural Science Foundation of Shandong Province(No.ZR2018BEM001)+1 种基金the Sichuan Science and Technology Program(No.2019YFH0046)the Basic and Advanced Research Project of CQ CSTC(No.cstc2017jcyjAX0381)。
文摘Deformation twin is one of the most important strain accommodation mechanisms and ultimately influences the mechanical properties for magnesium and its alloys.Especially,{1011}twin is usually thought to be closely related to the fracture or fatigue process of magnesium alloys.In the present work,the characteristics of microstructure near fracture region of deformed magnesium alloy have been investigated by a combination of electron back-scatter diffraction(EBSD)and transmission electron microscope(TEM).It has found that a large of deformation twins occur near fraction region,including{1012}and{1011}primary twins,{1011}-{1012}double twin and{1011}-{1012}-{1011}-{1012}quadruple twin.The actual boundaries of{1011}twins at atomic scale consist of{1011}coherent twinning boundaries(TBs)and parallel basal-pyramidal(BPy/Py B)planes.The tip of{1011}twin can even end up with BPy/Py B interfaces only.The experimental observations also reveal that when two{1011}twin variants sharing a common[1120]zone axis approach each other,the growth of one twin is usually hindered by the boundaries of the other twin.In addition,an apparent"crossing"phenomenon is also discovered when interaction of two{1011}twins takes place.According to these experimental observations,the possible underlying mechanisms behind such phenomena are proposed and discussed.These finding are expected to provide an insight into understanding the twinning behavior and the relationship between twin and fracture in magnesium and other materials with hexagonal structure.
基金support provided by the National Natural Science Fuulaliunl uf Cuild(Nu.51705435 auul Nu.51627806)key project of Sichuan Department of Science and Technology(No.2018JZ0048)Fundamental Research Funds for the Central Universities(2018GF05).
文摘In this study,spherical and mesoporous NiAl particles(abbreviated as sNiAl and mNiAl)were introduced as lubricant additives into two alkyl-imidazolium ionic liquids(ILs)(l-butyl-3-methylimidazolium tetrafluoroborate(LB104)and l-butyl-3-methyl imidazolium hexafluorophosphate(LP104))to explore their tribological properties.The sNiAl and mNiAl particles were modified in-situ by anion and cation moieties of ILs through chemical interaction,thereby enhancing their dispersibility and stability in ILs.The mNiAl particles have better dispersibility than the sNiAl ones in ILs because of high specific surface area.LP104-modified sNiAl particles show better friction reduction and wear resistance,mainly relying on the synergy of the hybrid lubricant.These particles form a protective layer that prevents friction pairs from straight asperity contact and improves the tribological behaviors.
