The dual transmitter implements the equivalent anti-magnetic flux transient electromagnetic method, which can effectively reduce the scope of the transient electromagnetic detection blind area. However, this method is...The dual transmitter implements the equivalent anti-magnetic flux transient electromagnetic method, which can effectively reduce the scope of the transient electromagnetic detection blind area. However, this method is rarely reported in the detection of pipelines in urban geophysical exploration and the application of coal mines. Based on this, this paper realizes the equivalent anti-magnetic flux transient electromagnetic method based on the dual launcher. The suppression effect of this method on the blind area is analyzed by physical simulation. And the detection experiment of underground pipelines is carried out outdoors. The results show that the dual launcher can significantly reduce the turn-off time, thereby effectively reducing the impact of the blind area on the detection results, and the pipeline detection results verify the device’s effectiveness. Finally, based on the ground experimental results, the application prospect of mine advanced detection is discussed. Compared with other detection fields, the formation of blind areas is mainly caused by the equipment. If the dual launcher can be used to reduce the blind area, the accuracy of advanced detection can be improved more effectively. The above research results are of great significance for improving the detection accuracy of the underground transient electromagnetic method.展开更多
Macroscale superlubricity has attracted increasing attention owing to its high significance in engineering and economics.We report the superlubricity of engineering materials by the addition of partially oxidized blac...Macroscale superlubricity has attracted increasing attention owing to its high significance in engineering and economics.We report the superlubricity of engineering materials by the addition of partially oxidized black phosphorus(oBP)in an oleic acid(OA)oil environment.The phosphorus oxides produced by active oxidation exhibit lower friction and quick deposition performance compared to BP particles.The H-bond(–COOH…O–P,or–COOH…O=P)formed between P–O bond(or P=O)and OA molecule could benefit the lubricating state and decrease the possibility of direct contact between rough peaks.The analysis of the worn surface indicates that a three-layer tribofilm consisting of amorphous carbon,BP crystal,and phosphorus oxide forms during the friction,which replaces the shear interface from the steel/steel to carbon–oBP/carbon–oBP layer and enables macroscale superlubricity.展开更多
In recent years, a new 2D-layered material—black phosphorus(BP)—has been a rising star after the era of graphene owing to its high charge carrier mobility, tunable direct bandgap and unique in-plane anisotropic stru...In recent years, a new 2D-layered material—black phosphorus(BP)—has been a rising star after the era of graphene owing to its high charge carrier mobility, tunable direct bandgap and unique in-plane anisotropic structure. With the development of the synthesis and modification methods of BP, its extensive applications, e.g., transistors, batteries and optoelectronics have emerged. In order to explore its full potential, research into the tribological properties of BP 2D-layered materials such as lubrication additives and fillers in self-lubricating composite materials would be not only of high scientific value but also of practical significance. In this work, recent advances on the friction and lubrication properties of BP nanosheets made by our group, including the micro-friction properties, the lubrication properties of BP nanosheets as water-based and oil-based lubrication additives, and the friction and wear of BP/PVDF composites will be presented. Finally, the future challenges and opportunities in the use of BP materials as lubricants will be discussed.展开更多
Self-lubricating polymer composite coatings,with tailorable tribological and mechanical properties,have been widely employed on mechanical parts to reduce friction and wear,which saves energy and improves the overall ...Self-lubricating polymer composite coatings,with tailorable tribological and mechanical properties,have been widely employed on mechanical parts to reduce friction and wear,which saves energy and improves the overall performance for applications such as aerospace satellite parts,shafts,gears,and bushings.The addition of functional fillers can overcome the limitations of single-polymer coatings and extend the service life of the coatings by providing a combination of low friction,high wear resistance,high load bearing,high temperature resistance,and high adhesion.This paper compares the heat resistance,and the tribological and mechanical properties of common polymer matrices,as well as the categories of functional fillers that improve the coating performance.Applicable scopes,process parameters,advantages,and limitations of the preparation methods of polymer coatings are discussed in detail.The tribological properties of the composite coatings with different matrices and fillers are compared,and the lubrication mechanisms are analyzed.Fillers reduce friction by promoting the formation of transfer films or liquid shear films.Improvement of the mechanical properties of the composite coatings with fillers of different morphologies is described in terms of strengthening and toughening mechanisms,including a stress transfer mechanism,shear yielding,crack bridging,and interfacial debonding.The test and enhancement methods for the adhesion properties between the coating and substrate are discussed.The coating adhesion can be enhanced through mechanical treatment,chemical treatment,and energy treatment of the substrate.Finally,we propose the design strategies for high-performance polymer composite coating systems adapted to specific operating conditions,and the limitations of current polymer composite coating research are identified.展开更多
In modern electric equipment,especially electric vehicles,inverter control systems can lead to complex shaft voltages and bearing currents.Within an electric motor,many parts have electrical failure problems,and among...In modern electric equipment,especially electric vehicles,inverter control systems can lead to complex shaft voltages and bearing currents.Within an electric motor,many parts have electrical failure problems,and among which bearings are the most sensitive and vulnerable components.In recent years,electrical failures in bearing have been frequently reported in electric vehicles,and the electrical failure of bearings has become a key issue that restricts the lifetime of all‐electric motor‐based power systems in a broader sense.The purpose of this review is to provide a comprehensive overview of the bearing premature failure in the mechanical systems exposed in an electrical environment represented by electric vehicles.The electrical environments in which bearing works including the different components and the origins of the shaft voltages and bearing currents,as well as the typical modes of electrical bearing failure including various topographical damages and lubrication failures,have been discussed.The fundamental influence mechanisms of voltage/current on the friction/lubrication properties have been summarized and analyzed,and corresponding countermeasures have been proposed.Finally,a brief introduction to the key technical flaws in the current researches will be made and the future outlook of frontier directions will be discussed.展开更多
In recent years, attempts to improve the mechanical properties of composites have increased remarkably owing to the inadequate utilization of matrices in demanding technological systems where efficiency, durability, a...In recent years, attempts to improve the mechanical properties of composites have increased remarkably owing to the inadequate utilization of matrices in demanding technological systems where efficiency, durability, and environmental compatibility are the key requirements. The search for novel materials that can potentially have enhanced mechanical properties continues. Recent studies have demonstrated that two-dimensional (2D) nanomaterials can act as excellent reinforcements because they possess high modulus of elasticity, high strength, and ultralow friction. By incorporating 2D nanomaterials in a composite, 2D nanomaterial-based composites (2DNBCs) have been developed. In view of this, a critical review of recent mechanical and tribological studies based on 2DNBCs has been undertaken. Matrices such as polymers, ceramics, and metals, as well as most of the representative 2D nanomaterial reinforcements such as graphene, boron nitride (BN), molybdenum disulfide (MoS2), and transition metal carbides and nitrides (MXenes) have been included in this review. Their preparation strategies, intrinsic mechanical properties, friction and lubrication performances, strengthening mechanisms, influencing factors, and potential applications have been comprehensively discussed. A brief summary and prospects are given in the final part, which would be useful in designing and fabricating advanced 2D nanocomposites in the future.展开更多
Ultralow friction polymer composites were prepared by adding oil-loaded microcapsules into epoxy(EP)resin.Mono-dispersed polystyrene(PS)/poly alpha olefin(PAO)microcapsules with a diameter of~2μm and a shell thicknes...Ultralow friction polymer composites were prepared by adding oil-loaded microcapsules into epoxy(EP)resin.Mono-dispersed polystyrene(PS)/poly alpha olefin(PAO)microcapsules with a diameter of~2μm and a shell thickness of~30 nm were prepared by solvent evaporation method in an oil-in-water emulsion.The lubrication behaviors of the EP resin composites with oil-loaded microcapsules have been investigated under different loads and sliding speeds.As compared with the pure EP resin,the friction coefficient of the composite could be reduced to 4%(from 0.71 to 0.028)and the wear rate could be decreased up to two orders of magnitude.It was demonstrated that the released PAO oil from the microcapsules during the friction process produced a boundary lubricating film,which could prevent the direct contact of two rubbing surfaces,and thus leading to an extremely low friction coefficient and wear rate.Moreover,the composites with microcapsules could achieve comparable lubrication properties to the case under the external lubrication condition,while the former case could effectively minimize the lubricant leakage and improve the lubrication efficiency.展开更多
Biomedical tribology has developed rapidly with the joint efforts of medical and tribological researchers,and it concerns various kinds of friction that existed inside and out side the body,such as the friction of joi...Biomedical tribology has developed rapidly with the joint efforts of medical and tribological researchers,and it concerns various kinds of friction that existed inside and out side the body,such as the friction of joints,the friction between skin and clothing,and the friction in the lumen(blood vessels,trachea,digestive tube,and excretory tube),which causes maiiy physiological changes and diseases in the human body.Besides,many medical devices have been used to treat or alleviate various diseases.Biomedical tribology plays a vital role in solving the widespread tribological issues in the medical devices field,aiming to improve the performance of medical devices and prolong the service life.展开更多
To utilize Cu-benzene-1,3,5-tricarboxylate(Cu-BTC)adsorbed lubricant oils in the self-lubricating field,the adsorption properties of Cu-BTC on different 1-olefins must be clarified.In this work,1-hexene,1-octene,1-non...To utilize Cu-benzene-1,3,5-tricarboxylate(Cu-BTC)adsorbed lubricant oils in the self-lubricating field,the adsorption properties of Cu-BTC on different 1-olefins must be clarified.In this work,1-hexene,1-octene,1-nonene,1-decene,1-undecene,and 1-dodecene were studied by the Monte Carlo method and experimentally.The adsorption limit of Cu-BTC for n-olefins was determined as 1-undecene by the adsorption isotherms.This suggested a limit for even straight-chain molecules to the adsorption of Cu-BTC.The maximum ratio of the olefin length of the largest pore diameter(L/D)of Cu-BTC was approximately 1.57.Furthermore,theoretical calculations(radial distribution function(RDF))and experiments(infrared(IR)spectra)confirmed the interaction of n-olefin adsorbates and the Cu-BTC framework occurred between the-CH=of olefins and the Cu and O atoms of the Cu-BTC framework.This work adds to the understanding and investigation of the adsorption of liquid lubricants using Cu-BTC as a metal-organic framework(MOF).展开更多
文摘The dual transmitter implements the equivalent anti-magnetic flux transient electromagnetic method, which can effectively reduce the scope of the transient electromagnetic detection blind area. However, this method is rarely reported in the detection of pipelines in urban geophysical exploration and the application of coal mines. Based on this, this paper realizes the equivalent anti-magnetic flux transient electromagnetic method based on the dual launcher. The suppression effect of this method on the blind area is analyzed by physical simulation. And the detection experiment of underground pipelines is carried out outdoors. The results show that the dual launcher can significantly reduce the turn-off time, thereby effectively reducing the impact of the blind area on the detection results, and the pipeline detection results verify the device’s effectiveness. Finally, based on the ground experimental results, the application prospect of mine advanced detection is discussed. Compared with other detection fields, the formation of blind areas is mainly caused by the equipment. If the dual launcher can be used to reduce the blind area, the accuracy of advanced detection can be improved more effectively. The above research results are of great significance for improving the detection accuracy of the underground transient electromagnetic method.
基金supported by the Beijing Natural Science Foundation(Grant No.JQ21008)the National Natural Science Foundation of China(Grant No.52275197)the Tsinghua-Foshan Innovation Special Fund(TFISF)(Grant No.2020THFS0127).
文摘Macroscale superlubricity has attracted increasing attention owing to its high significance in engineering and economics.We report the superlubricity of engineering materials by the addition of partially oxidized black phosphorus(oBP)in an oleic acid(OA)oil environment.The phosphorus oxides produced by active oxidation exhibit lower friction and quick deposition performance compared to BP particles.The H-bond(–COOH…O–P,or–COOH…O=P)formed between P–O bond(or P=O)and OA molecule could benefit the lubricating state and decrease the possibility of direct contact between rough peaks.The analysis of the worn surface indicates that a three-layer tribofilm consisting of amorphous carbon,BP crystal,and phosphorus oxide forms during the friction,which replaces the shear interface from the steel/steel to carbon–oBP/carbon–oBP layer and enables macroscale superlubricity.
基金support of the National Natural Science Foundation of China(Grant Nos.51527901,51335005,51475256,and 51605249)
文摘In recent years, a new 2D-layered material—black phosphorus(BP)—has been a rising star after the era of graphene owing to its high charge carrier mobility, tunable direct bandgap and unique in-plane anisotropic structure. With the development of the synthesis and modification methods of BP, its extensive applications, e.g., transistors, batteries and optoelectronics have emerged. In order to explore its full potential, research into the tribological properties of BP 2D-layered materials such as lubrication additives and fillers in self-lubricating composite materials would be not only of high scientific value but also of practical significance. In this work, recent advances on the friction and lubrication properties of BP nanosheets made by our group, including the micro-friction properties, the lubrication properties of BP nanosheets as water-based and oil-based lubrication additives, and the friction and wear of BP/PVDF composites will be presented. Finally, the future challenges and opportunities in the use of BP materials as lubricants will be discussed.
基金This work was supported by National Natural Science Foundation of China(Grant No.51822505)Beijing Natural Science Foundation of China(Grant No.3182010)+1 种基金Major Scientific Research and Development Project in Jiangxi(Grant No.20173ABC28008)the National Key Research and Development Program of China(Grant No.2018YFB2000202).
文摘Self-lubricating polymer composite coatings,with tailorable tribological and mechanical properties,have been widely employed on mechanical parts to reduce friction and wear,which saves energy and improves the overall performance for applications such as aerospace satellite parts,shafts,gears,and bushings.The addition of functional fillers can overcome the limitations of single-polymer coatings and extend the service life of the coatings by providing a combination of low friction,high wear resistance,high load bearing,high temperature resistance,and high adhesion.This paper compares the heat resistance,and the tribological and mechanical properties of common polymer matrices,as well as the categories of functional fillers that improve the coating performance.Applicable scopes,process parameters,advantages,and limitations of the preparation methods of polymer coatings are discussed in detail.The tribological properties of the composite coatings with different matrices and fillers are compared,and the lubrication mechanisms are analyzed.Fillers reduce friction by promoting the formation of transfer films or liquid shear films.Improvement of the mechanical properties of the composite coatings with fillers of different morphologies is described in terms of strengthening and toughening mechanisms,including a stress transfer mechanism,shear yielding,crack bridging,and interfacial debonding.The test and enhancement methods for the adhesion properties between the coating and substrate are discussed.The coating adhesion can be enhanced through mechanical treatment,chemical treatment,and energy treatment of the substrate.Finally,we propose the design strategies for high-performance polymer composite coating systems adapted to specific operating conditions,and the limitations of current polymer composite coating research are identified.
基金supported by the National Natural Science Foundation of China(Grant Nos.51822505 and 51527901)Tsinghua University Initiative Scientific Research Program(Grant No.2019Z08QCX11)Beijing Natural Science Foundation of China(Grant No.3182010)
文摘In modern electric equipment,especially electric vehicles,inverter control systems can lead to complex shaft voltages and bearing currents.Within an electric motor,many parts have electrical failure problems,and among which bearings are the most sensitive and vulnerable components.In recent years,electrical failures in bearing have been frequently reported in electric vehicles,and the electrical failure of bearings has become a key issue that restricts the lifetime of all‐electric motor‐based power systems in a broader sense.The purpose of this review is to provide a comprehensive overview of the bearing premature failure in the mechanical systems exposed in an electrical environment represented by electric vehicles.The electrical environments in which bearing works including the different components and the origins of the shaft voltages and bearing currents,as well as the typical modes of electrical bearing failure including various topographical damages and lubrication failures,have been discussed.The fundamental influence mechanisms of voltage/current on the friction/lubrication properties have been summarized and analyzed,and corresponding countermeasures have been proposed.Finally,a brief introduction to the key technical flaws in the current researches will be made and the future outlook of frontier directions will be discussed.
基金The authors gratefully acknowledge the financial support from the National Natural Science Foundation of China(Grant No.51822505)Major Scientific Research and Development Project in Jiangxi(Grant No.20173ABC28008)+2 种基金Tsinghua University Initiative Scientific Research Program(Grant No.2019Z08QCX11)Beijing Natural Science Foundation of China(Grant No.3182010)The authors thank Dr.Jie CHENG,Feng HE,Dr.Xiao YANG,Zhendong LIAO,and Guangzhi XIONG for their invaluable contributions to this collaboration.
文摘In recent years, attempts to improve the mechanical properties of composites have increased remarkably owing to the inadequate utilization of matrices in demanding technological systems where efficiency, durability, and environmental compatibility are the key requirements. The search for novel materials that can potentially have enhanced mechanical properties continues. Recent studies have demonstrated that two-dimensional (2D) nanomaterials can act as excellent reinforcements because they possess high modulus of elasticity, high strength, and ultralow friction. By incorporating 2D nanomaterials in a composite, 2D nanomaterial-based composites (2DNBCs) have been developed. In view of this, a critical review of recent mechanical and tribological studies based on 2DNBCs has been undertaken. Matrices such as polymers, ceramics, and metals, as well as most of the representative 2D nanomaterial reinforcements such as graphene, boron nitride (BN), molybdenum disulfide (MoS2), and transition metal carbides and nitrides (MXenes) have been included in this review. Their preparation strategies, intrinsic mechanical properties, friction and lubrication performances, strengthening mechanisms, influencing factors, and potential applications have been comprehensively discussed. A brief summary and prospects are given in the final part, which would be useful in designing and fabricating advanced 2D nanocomposites in the future.
基金supported by the National Natural Science Foundation of China(Grant Nos.51822505,51811530014,and 51605008)Beijing Natural Science Foundation of China(Grant No.3182010)。
文摘Ultralow friction polymer composites were prepared by adding oil-loaded microcapsules into epoxy(EP)resin.Mono-dispersed polystyrene(PS)/poly alpha olefin(PAO)microcapsules with a diameter of~2μm and a shell thickness of~30 nm were prepared by solvent evaporation method in an oil-in-water emulsion.The lubrication behaviors of the EP resin composites with oil-loaded microcapsules have been investigated under different loads and sliding speeds.As compared with the pure EP resin,the friction coefficient of the composite could be reduced to 4%(from 0.71 to 0.028)and the wear rate could be decreased up to two orders of magnitude.It was demonstrated that the released PAO oil from the microcapsules during the friction process produced a boundary lubricating film,which could prevent the direct contact of two rubbing surfaces,and thus leading to an extremely low friction coefficient and wear rate.Moreover,the composites with microcapsules could achieve comparable lubrication properties to the case under the external lubrication condition,while the former case could effectively minimize the lubricant leakage and improve the lubrication efficiency.
文摘Biomedical tribology has developed rapidly with the joint efforts of medical and tribological researchers,and it concerns various kinds of friction that existed inside and out side the body,such as the friction of joints,the friction between skin and clothing,and the friction in the lumen(blood vessels,trachea,digestive tube,and excretory tube),which causes maiiy physiological changes and diseases in the human body.Besides,many medical devices have been used to treat or alleviate various diseases.Biomedical tribology plays a vital role in solving the widespread tribological issues in the medical devices field,aiming to improve the performance of medical devices and prolong the service life.
基金The National Natural Science Foundation of China(Grant No.51905297)Natural Science Foundation of Hebei Province of China(Grant No.E2021203092)the Opening Foundation of State Key Laboratory of Tribology,Tsinghua University(Grant No.SKLTKF21B13)are acknowledged.
文摘To utilize Cu-benzene-1,3,5-tricarboxylate(Cu-BTC)adsorbed lubricant oils in the self-lubricating field,the adsorption properties of Cu-BTC on different 1-olefins must be clarified.In this work,1-hexene,1-octene,1-nonene,1-decene,1-undecene,and 1-dodecene were studied by the Monte Carlo method and experimentally.The adsorption limit of Cu-BTC for n-olefins was determined as 1-undecene by the adsorption isotherms.This suggested a limit for even straight-chain molecules to the adsorption of Cu-BTC.The maximum ratio of the olefin length of the largest pore diameter(L/D)of Cu-BTC was approximately 1.57.Furthermore,theoretical calculations(radial distribution function(RDF))and experiments(infrared(IR)spectra)confirmed the interaction of n-olefin adsorbates and the Cu-BTC framework occurred between the-CH=of olefins and the Cu and O atoms of the Cu-BTC framework.This work adds to the understanding and investigation of the adsorption of liquid lubricants using Cu-BTC as a metal-organic framework(MOF).
