Difficult-to-machine materials (DMMs) are extensively applied in critical fields such as aviation,semiconductor,biomedicine,and other key fields due to their excellent material properties.However,traditional machining...Difficult-to-machine materials (DMMs) are extensively applied in critical fields such as aviation,semiconductor,biomedicine,and other key fields due to their excellent material properties.However,traditional machining technologies often struggle to achieve ultra-precision with DMMs resulting from poor surface quality and low processing efficiency.In recent years,field-assisted machining (FAM) technology has emerged as a new generation of machining technology based on innovative principles such as laser heating,tool vibration,magnetic magnetization,and plasma modification,providing a new solution for improving the machinability of DMMs.This technology not only addresses these limitations of traditional machining methods,but also has become a hot topic of research in the domain of ultra-precision machining of DMMs.Many new methods and principles have been introduced and investigated one after another,yet few studies have presented a comprehensive analysis and summarization.To fill this gap and understand the development trend of FAM,this study provides an important overview of FAM,covering different assisted machining methods,application effects,mechanism analysis,and equipment design.The current deficiencies and future challenges of FAM are summarized to lay the foundation for the further development of multi-field hybrid assisted and intelligent FAM technologies.展开更多
Investigations of technological characteristics and bonding mechanism of field-assisted bonding are done, which are for bonding of electrolytes (Pyrex glass) to monocrystal silicon and aluminum. The features of micros...Investigations of technological characteristics and bonding mechanism of field-assisted bonding are done, which are for bonding of electrolytes (Pyrex glass) to monocrystal silicon and aluminum. The features of microstructure and the distribution of the diffused elements in the bonding interface area are studied by means of SEM, EDX and XRD, and the influence of the technological factors on the bonding process is also studied. The model of 'metal-oxides-glass' of bonding structure and ions diffusion and bonding in the condition of electrical field-assisted are indicated.展开更多
Soda-lime glasses were treated by electric field-assisted diffusion(EFAD) process. The mechanical properties and structural evolution on both glass anode and cathode surfaces were investigated, respectively. It was ...Soda-lime glasses were treated by electric field-assisted diffusion(EFAD) process. The mechanical properties and structural evolution on both glass anode and cathode surfaces were investigated, respectively. It was found that the EFAD resulted in the formation of a Na depletion layer on anode surface, which caused the relaxation of the glass anode surface network and the formation of a number of defects. Correspondingly, the hardness and flexural strength declined in anode surface compared to that of the original glass. On the other hand, the EFAD also created a compressive layer on cathode surface, causing the improvement of the hardness and flexural strength on cathode surface. The defected structure could be reconstructed by additional annealing process.展开更多
Manufacturing flexible magnetic-driven actuators with complex structures and magnetic arrangements to achieve diverse functionalities is becoming a popular trend.Among various manufacturing technologies,magnetic-assis...Manufacturing flexible magnetic-driven actuators with complex structures and magnetic arrangements to achieve diverse functionalities is becoming a popular trend.Among various manufacturing technologies,magnetic-assisted digital light processing(DLP)stands out because it enables precise manufacturing of macro-scale structures and micro-scale distributions with the assistance of an external magnetic field.Current research on manufacturing magnetic flexible actuators mostly employs single materials,which limits the magnetic driving performance to some extent.Based on these characterizations,we propose a multi-material magnetic field-assisted DLP technology to produce flexible actuators with an accuracy of 200μm.The flexible actuators are printed using two materials with different mechanical and magnetic properties.Considering the interface connectivity of multi-material printing,the effect of interfaces on mechanical properties is also explored.Experimental results indicate good chemical affinity between the two materials we selected.The overlap or connection length of the interface moderately improves the tensile strength of multi-material structures.In addition,we investigate the influence of the volume fraction of the magnetic part on deformation.Simulation and experimental results indicate that increasing the volume ratio(20%to 50%)of the magnetic structure can enhance the responsiveness of the actuator(more than 50%).Finally,we successfully manufacture two multi-material flexible actuators with specific magnetic arrangements:a multi-legged crawling robot and a flexible gripper capable of crawling and grasping actions.These results confirm that this method will pave the way for further research on the precise fabrication of magnetic flexible actuators with diverse functionalities.展开更多
Energy field-assisted machining technology has the potential to overcome the limitations of machining difficult-to-machine metal materials,such as poor machinability,low cutting efficiency,and high energy consumption....Energy field-assisted machining technology has the potential to overcome the limitations of machining difficult-to-machine metal materials,such as poor machinability,low cutting efficiency,and high energy consumption.High-speed dry milling has emerged as a typical green processing technology due to its high processing efficiency and avoidance of cutting fluids.However,the lack of necessary cooling and lubrication in high-speed dry milling makes it difficult to meet the continuous milling requirements for difficult-to-machine metal materials.The introduction of advanced energy-field-assisted green processing technology can improve the machinability of such metallic materials and achieve efficient precision manufacturing,making it a focus of academic and industrial research.In this review,the characteristics and limitations of high-speed dry milling of difficult-to-machine metal materials,including titanium alloys,nickel-based alloys,and high-strength steel,are systematically explored.The laser energy field,ultrasonic energy field,and cryogenic minimum quantity lubrication energy fields are introduced.By analyzing the effects of changing the energy field and cutting parameters on tool wear,chip morphology,cutting force,temperature,and surface quality of the workpiece during milling,the superiority of energy-field-assisted milling of difficult-to-machine metal materials is demonstrated.Finally,the shortcomings and technical challenges of energy-field-assisted milling are summarized in detail,providing feasible ideas for realizing multi-energy field collaborative green machining of difficult-to-machine metal materials in the future.展开更多
A novel Y_(3)Si_(2)C_(2)material was synthesized at a relatively low temperature(900℃)using a molten salt method for the first time,and subsequently used as the joining material for carbon fiber reinforced SiC(Cf/SiC...A novel Y_(3)Si_(2)C_(2)material was synthesized at a relatively low temperature(900℃)using a molten salt method for the first time,and subsequently used as the joining material for carbon fiber reinforced SiC(Cf/SiC)composites.The sound near-seamless joints with no obvious remaining interlayer were obtained at 1600℃using an electric field-assisted sintering technique(FAST).During joining,a liquid phase was formed by the eutectic reaction among Y_(3)Si_(2)C_(2),γ(Y–C)phase,and SiC,followed by the precipitation of SiC particles.The presence of the liquid promoted the sintering of newly formed SiC particles,leading to their complete consolidation with the Cf/SiC matrix.On the other hand,the excess of the liquid was pushed away from the joining area under the effect of a uniaxial pressure of 30 MPa,leading to the formation of the near-seamless joints.The highest shear strength(Ä)of 17.2±2.9 MPa was obtained after being joined at 1600℃for 10 min.The failure of the joints occurred in the Cf/SiC matrix,indicating that the interface was stronger than that of the Cf/SiC matrix.The formation of a near-seamless joint minimizes the mismatch of thermal expansion coefficients and also irradiation-induced swelling,suggesting that the proposed joining strategy can be potentially applied to SiC-based ceramic matrix composites(CMCs)for extreme environmental applications.展开更多
The exponential-doping GaN nanowire arrays(GaN NWAs)photocathode has a"light-trapping effect",and the built-in electric field can promote the concentration of the photogene rated carrier center to the top su...The exponential-doping GaN nanowire arrays(GaN NWAs)photocathode has a"light-trapping effect",and the built-in electric field can promote the concentration of the photogene rated carrier center to the top surface of the nanowire.However,in the preparation ofactual NWAs photocathodes,the problem that photons emitted from the sides of the nanowires cannot be effectively collected has been encountered.Our proposed field-assisted exponential-doping GaN NWAs can bend the motion trajectory of the emitted electrons toward the collecting side.In this study,the quantum efficiency(QE)and collection efficiency(CE)of the external field-assisted exponential-doping GaN NWAs photocathode are derived based on the two-dimensional carrier diffusion equation and the initial energy and angular distribution,respectively.For a field-assisted exponential-doping GaN NWAs with a width d=200 nm and a height H=400 nm,the optimal structural parameters are obtained:the incident angleθ=50°and the nanowire spacing is L=335.6 nm.On this basis,the field intensity of 0.5 V/μm can maximize the CE of the NWAs.All the results show that the field-assisted approach does contribute to the collection of emitted electrons,which can provide theoretical guidance for high-performance electron sources based on exponential-doping GaN NWAs photocathodes.And field-assisted exponential-doping GaN NWAs cathode is expected to be verified by the experimental results in the future.展开更多
Charge transfer mechanisms of contact electrification(CE)are essential for widening applications of the triboelectric nanogenerator,and thus are widely studied by scientists around the world.However,the quantitative m...Charge transfer mechanisms of contact electrification(CE)are essential for widening applications of the triboelectric nanogenerator,and thus are widely studied by scientists around the world.However,the quantitative modeling of CE,especially that between polymers,is still lacking.Herein,a model was proposed to describe the contributions from different mechanisms,including electron transfer and mass transfer in polymer/polymer CE through the fieldassisted thermionic emission,where three groups of charge transfer mechanisms were distinguished by the polarity of the charge transfer and the corresponding electric field.The results indicated that the total generated charge in CE is actually much larger than the measured net surface charge,confirming the bidirectional material-dependent charge transfer mechanisms between two surfaces,which is meaningful for understanding the millennium puzzle in triboelectrification and provides a new perspective for promoting the applications to tailor surface charge generation.展开更多
Silver nanoclusters(NCs) embedded in soda-lime glass was synthesized by the electric fieldassisted diffusion(EFAD) and successive annealing. The samples were characterized by UV-Vis absorption spectroscopy, photol...Silver nanoclusters(NCs) embedded in soda-lime glass was synthesized by the electric fieldassisted diffusion(EFAD) and successive annealing. The samples were characterized by UV-Vis absorption spectroscopy, photoluminescence spectroscopy, X-ray photoelectron spectroscopy(XPS), and lifetime measurements. The experimental results show that the growth of silver clusters is favored by the annealing temperature and dwell time. The as-diffused and annealed glass samples show photoluminescence around 550 nm under UV excitation, which can be associated with the presence of L-center and Ag3~+ cluster. And the increasing of the annealing temperature and dwell time results in an appearance of the SPR peak and the decreasing of the luminescence intensities because the Ag3~+ clusters grow up into the Ag nanoparticles.展开更多
In this study,the effect of transverse magnetic field-assisted directional solidification(MFADS)on the microstructures in Ni-Mn-Ga alloys has been investigated.The results show that the magnetic field is capable of in...In this study,the effect of transverse magnetic field-assisted directional solidification(MFADS)on the microstructures in Ni-Mn-Ga alloys has been investigated.The results show that the magnetic field is capable of inducing transversal macrosegregation perpendicular to the magnetic field,causing the emergence of martensite clusters in the austenite matrix.Moreover,the magnetic field alleviates the microseg-regation on a dendritic scale and promotes the preferred growth of austenite dendrites.On the basis of the above investigation,several special samples are designed using the MFADS to study the crystallographic evolution and mechanical behavior during thermal/stress-induced martensite transformation.The martensite cluster in the austenite matrix is used to investigate the martensite transformation and growth under cooling-heating cycles.The crystallographic relationship and phase boundary microstructure between martensite and austenite have been characterized.In addition,the microsegregation on a dendritic scale can significantly influence the martensite variant distribution,corresponding to the performance during compressive circles based on the analysis of the deformation gradient tensor.The stress-induced superelasticity is closely dependent on orientation,well explained from the perspective of different resolved shear stress factors and correspondence variant pair formation transformation strain.The crystallographic evolution has been characterized during in-situ stress-induced transformation.The findings not only deepen the understanding of martensite transformation and mechanical behavior under a thermal/stress field in Ni-Mn-Ga alloys but also propose a promising strategy to obtain microstructure-controllable functional alloys by MFADS.展开更多
Rechargeable batteries are essential for the increased demand for energy storage technologies due to their ability to adapt intermittent renewable energies into electric devices,such as electric vehicles.To boost the ...Rechargeable batteries are essential for the increased demand for energy storage technologies due to their ability to adapt intermittent renewable energies into electric devices,such as electric vehicles.To boost the battery performance,applying external fields to assist the electrochemical process has been developed and exhibits significant merits in energy efficiency and cycle stability enhancement.This perspective focuses on recent advances in the development of external field–assisted battery technologies,including photo-assisted,magnetic field–assisted,sound field–assisted,and multiple field–assisted.The workingmechanisms of external field–assisted batteries and their challenges and opportunities are highlighted.展开更多
Electricity is an efficient form of energy,and the growing interest in electricity-assisted manufacturing is motivated by its inherent energy saving and reduced environmental impact.Beyond this,Electromagnetic Process...Electricity is an efficient form of energy,and the growing interest in electricity-assisted manufacturing is motivated by its inherent energy saving and reduced environmental impact.Beyond this,Electromagnetic Processing of Materials(EPM)allows the fabrication of materials with new compositions,metastable phases and nanograined microstructures that cannot be obtained using conventional heating processes using furnaces.This review covers EPM for the manufacture of ceramic and metal bulk components,with a specific focus on the effects of electric fields and electromagnetic radiations on processing in a wide spectrum of frequencies ranging from DC(f=0 Hz)to visible light(f=10^(14)–10^(15)Hz).The manuscript is divided into two parts.The first part provides a comprehensive overview of the interactions between matter and electric field/current,including heating phenomena(resistive Joule,induction,dielectric heating,electric arcs)and athermal effects(electromigration,electroplasticity,electrochemical reactions,ponderomotive force and others).The second part is focused on the technological application of the techniques,covering heat treatments,joining,sintering and forming.Seven distinct physical phenomena are involved in EPM:resistive Joule and induction heating,electrochemical reactions,electroplasticity,electric arcs and electromagnetic heating based on radio and microwave frequencies(mainly used for heating dielectric materials;i.e.,dielectric heating)or on the IR/visible light(IR heating and lasers).展开更多
Processing of materials in the form of ceramics normally involves several steps including calcination at a relatively low temperature for synthesis of the end-product powder and sintering at a high temperature for den...Processing of materials in the form of ceramics normally involves several steps including calcination at a relatively low temperature for synthesis of the end-product powder and sintering at a high temperature for densification.The work we have been developing introduces a novel approach enabling synthesis plus sintering of materials in a single running experiment by using electric fields,ending with dense ceramics that display grains noticeably finer than in conventional processing.This new paradigm is fully illustrated with experiments conducted on amorphous CaCu3Ti4O12 precursor powder,shown to experience,on heating,crystallization through intermediate phases,followed by chemical reaction leading to synthesis of the end-product powder,plus densification depending on field adjustment.The processing time and furnace temperature are considerably reduced,demonstrating that enhanced synthesis and sintering rates applied under field input.Similar results found in Bi2/3Cu3Ti4O12are also shown.The different factors that may contribute to this unique scenario,including Joule heating,defect generation,and reduction of free energy for nuclei formation promoted by the applied field,are briefly discussed.Overall,the findings we bring here are exclusive as they show an exploitable way that allows rapid processing of materials with good control over particle and grain coarsening.展开更多
基金supported by the National Key Research and Development Project of China (Grant No.2023YFB3407200)the National Natural Science Foundation of China (Grant Nos.52225506,52375430,and 52188102)the Program for HUST Academic Frontier Youth Team (Grant No.2019QYTD12)。
文摘Difficult-to-machine materials (DMMs) are extensively applied in critical fields such as aviation,semiconductor,biomedicine,and other key fields due to their excellent material properties.However,traditional machining technologies often struggle to achieve ultra-precision with DMMs resulting from poor surface quality and low processing efficiency.In recent years,field-assisted machining (FAM) technology has emerged as a new generation of machining technology based on innovative principles such as laser heating,tool vibration,magnetic magnetization,and plasma modification,providing a new solution for improving the machinability of DMMs.This technology not only addresses these limitations of traditional machining methods,but also has become a hot topic of research in the domain of ultra-precision machining of DMMs.Many new methods and principles have been introduced and investigated one after another,yet few studies have presented a comprehensive analysis and summarization.To fill this gap and understand the development trend of FAM,this study provides an important overview of FAM,covering different assisted machining methods,application effects,mechanism analysis,and equipment design.The current deficiencies and future challenges of FAM are summarized to lay the foundation for the further development of multi-field hybrid assisted and intelligent FAM technologies.
基金This project is supported by Foundation of Taiyuan University of Technology "211" Project, China (No.20304006).
文摘Investigations of technological characteristics and bonding mechanism of field-assisted bonding are done, which are for bonding of electrolytes (Pyrex glass) to monocrystal silicon and aluminum. The features of microstructure and the distribution of the diffused elements in the bonding interface area are studied by means of SEM, EDX and XRD, and the influence of the technological factors on the bonding process is also studied. The model of 'metal-oxides-glass' of bonding structure and ions diffusion and bonding in the condition of electrical field-assisted are indicated.
基金Funded by Shanghai Science and Technology Committee(No.12nm0504700)
文摘Soda-lime glasses were treated by electric field-assisted diffusion(EFAD) process. The mechanical properties and structural evolution on both glass anode and cathode surfaces were investigated, respectively. It was found that the EFAD resulted in the formation of a Na depletion layer on anode surface, which caused the relaxation of the glass anode surface network and the formation of a number of defects. Correspondingly, the hardness and flexural strength declined in anode surface compared to that of the original glass. On the other hand, the EFAD also created a compressive layer on cathode surface, causing the improvement of the hardness and flexural strength on cathode surface. The defected structure could be reconstructed by additional annealing process.
基金support from the National Natural Science Foundation of China(Grant No.52205424)the Natural Science Foundation of Zhejiang Province for Distinguished Young Scholars of China(Grant No.LR22E050002)+1 种基金the“Pioneer”and“Leading Goose”R&D Program of Zhejiang Province of China(Grant No.2023C01170)the Zhejiang Provincial Natural Science Foundation of China(Grant No.LY23A020001).
文摘Manufacturing flexible magnetic-driven actuators with complex structures and magnetic arrangements to achieve diverse functionalities is becoming a popular trend.Among various manufacturing technologies,magnetic-assisted digital light processing(DLP)stands out because it enables precise manufacturing of macro-scale structures and micro-scale distributions with the assistance of an external magnetic field.Current research on manufacturing magnetic flexible actuators mostly employs single materials,which limits the magnetic driving performance to some extent.Based on these characterizations,we propose a multi-material magnetic field-assisted DLP technology to produce flexible actuators with an accuracy of 200μm.The flexible actuators are printed using two materials with different mechanical and magnetic properties.Considering the interface connectivity of multi-material printing,the effect of interfaces on mechanical properties is also explored.Experimental results indicate good chemical affinity between the two materials we selected.The overlap or connection length of the interface moderately improves the tensile strength of multi-material structures.In addition,we investigate the influence of the volume fraction of the magnetic part on deformation.Simulation and experimental results indicate that increasing the volume ratio(20%to 50%)of the magnetic structure can enhance the responsiveness of the actuator(more than 50%).Finally,we successfully manufacture two multi-material flexible actuators with specific magnetic arrangements:a multi-legged crawling robot and a flexible gripper capable of crawling and grasping actions.These results confirm that this method will pave the way for further research on the precise fabrication of magnetic flexible actuators with diverse functionalities.
基金supported by the National Key R&D Program of China(Grant No.2020YFB2010500).
文摘Energy field-assisted machining technology has the potential to overcome the limitations of machining difficult-to-machine metal materials,such as poor machinability,low cutting efficiency,and high energy consumption.High-speed dry milling has emerged as a typical green processing technology due to its high processing efficiency and avoidance of cutting fluids.However,the lack of necessary cooling and lubrication in high-speed dry milling makes it difficult to meet the continuous milling requirements for difficult-to-machine metal materials.The introduction of advanced energy-field-assisted green processing technology can improve the machinability of such metallic materials and achieve efficient precision manufacturing,making it a focus of academic and industrial research.In this review,the characteristics and limitations of high-speed dry milling of difficult-to-machine metal materials,including titanium alloys,nickel-based alloys,and high-strength steel,are systematically explored.The laser energy field,ultrasonic energy field,and cryogenic minimum quantity lubrication energy fields are introduced.By analyzing the effects of changing the energy field and cutting parameters on tool wear,chip morphology,cutting force,temperature,and surface quality of the workpiece during milling,the superiority of energy-field-assisted milling of difficult-to-machine metal materials is demonstrated.Finally,the shortcomings and technical challenges of energy-field-assisted milling are summarized in detail,providing feasible ideas for realizing multi-energy field collaborative green machining of difficult-to-machine metal materials in the future.
基金This study was supported by the National Natural Science Foundation of China(Grant No.11975296)the Natural Science Foundation of Ningbo City(Grant No.2021J199)+3 种基金We would like to recognize the support from the Ningbo 3315 Innovative Teams Program,China(Grant No.2019A-14-C)Peter TATARKO gratefully acknowledges the financial support of the project APVV-17-0328this study was performed as part of the implementation of the project“Building-up Centre for advanced materials application of the Slovak Academy of Sciences”and ITMS project(Grant No.313021T081)supported by the Research&Innovation Operational Programme funded by the ERDF.
文摘A novel Y_(3)Si_(2)C_(2)material was synthesized at a relatively low temperature(900℃)using a molten salt method for the first time,and subsequently used as the joining material for carbon fiber reinforced SiC(Cf/SiC)composites.The sound near-seamless joints with no obvious remaining interlayer were obtained at 1600℃using an electric field-assisted sintering technique(FAST).During joining,a liquid phase was formed by the eutectic reaction among Y_(3)Si_(2)C_(2),γ(Y–C)phase,and SiC,followed by the precipitation of SiC particles.The presence of the liquid promoted the sintering of newly formed SiC particles,leading to their complete consolidation with the Cf/SiC matrix.On the other hand,the excess of the liquid was pushed away from the joining area under the effect of a uniaxial pressure of 30 MPa,leading to the formation of the near-seamless joints.The highest shear strength(Ä)of 17.2±2.9 MPa was obtained after being joined at 1600℃for 10 min.The failure of the joints occurred in the Cf/SiC matrix,indicating that the interface was stronger than that of the Cf/SiC matrix.The formation of a near-seamless joint minimizes the mismatch of thermal expansion coefficients and also irradiation-induced swelling,suggesting that the proposed joining strategy can be potentially applied to SiC-based ceramic matrix composites(CMCs)for extreme environmental applications.
基金This work was supported financially by the Qing Lan Project of Jiangsu Province,China(No.2017-AD41779)the Fundamental Research Funds for the Central Universities-China(No.30916011206)the Six Talent Peaks Project in Jiangsu Province,China(No.2015-XCL-008).
文摘The exponential-doping GaN nanowire arrays(GaN NWAs)photocathode has a"light-trapping effect",and the built-in electric field can promote the concentration of the photogene rated carrier center to the top surface of the nanowire.However,in the preparation ofactual NWAs photocathodes,the problem that photons emitted from the sides of the nanowires cannot be effectively collected has been encountered.Our proposed field-assisted exponential-doping GaN NWAs can bend the motion trajectory of the emitted electrons toward the collecting side.In this study,the quantum efficiency(QE)and collection efficiency(CE)of the external field-assisted exponential-doping GaN NWAs photocathode are derived based on the two-dimensional carrier diffusion equation and the initial energy and angular distribution,respectively.For a field-assisted exponential-doping GaN NWAs with a width d=200 nm and a height H=400 nm,the optimal structural parameters are obtained:the incident angleθ=50°and the nanowire spacing is L=335.6 nm.On this basis,the field intensity of 0.5 V/μm can maximize the CE of the NWAs.All the results show that the field-assisted approach does contribute to the collection of emitted electrons,which can provide theoretical guidance for high-performance electron sources based on exponential-doping GaN NWAs photocathodes.And field-assisted exponential-doping GaN NWAs cathode is expected to be verified by the experimental results in the future.
文摘Charge transfer mechanisms of contact electrification(CE)are essential for widening applications of the triboelectric nanogenerator,and thus are widely studied by scientists around the world.However,the quantitative modeling of CE,especially that between polymers,is still lacking.Herein,a model was proposed to describe the contributions from different mechanisms,including electron transfer and mass transfer in polymer/polymer CE through the fieldassisted thermionic emission,where three groups of charge transfer mechanisms were distinguished by the polarity of the charge transfer and the corresponding electric field.The results indicated that the total generated charge in CE is actually much larger than the measured net surface charge,confirming the bidirectional material-dependent charge transfer mechanisms between two surfaces,which is meaningful for understanding the millennium puzzle in triboelectrification and provides a new perspective for promoting the applications to tailor surface charge generation.
基金Funded by the Shanghai Science and Technology Committee(12nm0504700)
文摘Silver nanoclusters(NCs) embedded in soda-lime glass was synthesized by the electric fieldassisted diffusion(EFAD) and successive annealing. The samples were characterized by UV-Vis absorption spectroscopy, photoluminescence spectroscopy, X-ray photoelectron spectroscopy(XPS), and lifetime measurements. The experimental results show that the growth of silver clusters is favored by the annealing temperature and dwell time. The as-diffused and annealed glass samples show photoluminescence around 550 nm under UV excitation, which can be associated with the presence of L-center and Ag3~+ cluster. And the increasing of the annealing temperature and dwell time results in an appearance of the SPR peak and the decreasing of the luminescence intensities because the Ag3~+ clusters grow up into the Ag nanoparticles.
基金financed by the National Natural Science Foundation of China(Nos.51904183 and 52130204)the Independent Research and Development Project of State Key Laboratory of Advanced Special Steel,Shanghai Key Laboratory of Advanced Ferrometallurgy,Shanghai University(No.SKLASS 2021-Z07)the Science and Technology Commission of Shanghai Municipality(Nos.19DZ2270200 and 20511107700).
文摘In this study,the effect of transverse magnetic field-assisted directional solidification(MFADS)on the microstructures in Ni-Mn-Ga alloys has been investigated.The results show that the magnetic field is capable of inducing transversal macrosegregation perpendicular to the magnetic field,causing the emergence of martensite clusters in the austenite matrix.Moreover,the magnetic field alleviates the microseg-regation on a dendritic scale and promotes the preferred growth of austenite dendrites.On the basis of the above investigation,several special samples are designed using the MFADS to study the crystallographic evolution and mechanical behavior during thermal/stress-induced martensite transformation.The martensite cluster in the austenite matrix is used to investigate the martensite transformation and growth under cooling-heating cycles.The crystallographic relationship and phase boundary microstructure between martensite and austenite have been characterized.In addition,the microsegregation on a dendritic scale can significantly influence the martensite variant distribution,corresponding to the performance during compressive circles based on the analysis of the deformation gradient tensor.The stress-induced superelasticity is closely dependent on orientation,well explained from the perspective of different resolved shear stress factors and correspondence variant pair formation transformation strain.The crystallographic evolution has been characterized during in-situ stress-induced transformation.The findings not only deepen the understanding of martensite transformation and mechanical behavior under a thermal/stress field in Ni-Mn-Ga alloys but also propose a promising strategy to obtain microstructure-controllable functional alloys by MFADS.
基金Innovation and Technology Commission of the Hong Kong Special Administrative Region,China,Grant/Award Number:ITS/219/21FP。
文摘Rechargeable batteries are essential for the increased demand for energy storage technologies due to their ability to adapt intermittent renewable energies into electric devices,such as electric vehicles.To boost the battery performance,applying external fields to assist the electrochemical process has been developed and exhibits significant merits in energy efficiency and cycle stability enhancement.This perspective focuses on recent advances in the development of external field–assisted battery technologies,including photo-assisted,magnetic field–assisted,sound field–assisted,and multiple field–assisted.The workingmechanisms of external field–assisted batteries and their challenges and opportunities are highlighted.
基金the Thousand Talents Program of China and Sichuan Province。
文摘Electricity is an efficient form of energy,and the growing interest in electricity-assisted manufacturing is motivated by its inherent energy saving and reduced environmental impact.Beyond this,Electromagnetic Processing of Materials(EPM)allows the fabrication of materials with new compositions,metastable phases and nanograined microstructures that cannot be obtained using conventional heating processes using furnaces.This review covers EPM for the manufacture of ceramic and metal bulk components,with a specific focus on the effects of electric fields and electromagnetic radiations on processing in a wide spectrum of frequencies ranging from DC(f=0 Hz)to visible light(f=10^(14)–10^(15)Hz).The manuscript is divided into two parts.The first part provides a comprehensive overview of the interactions between matter and electric field/current,including heating phenomena(resistive Joule,induction,dielectric heating,electric arcs)and athermal effects(electromigration,electroplasticity,electrochemical reactions,ponderomotive force and others).The second part is focused on the technological application of the techniques,covering heat treatments,joining,sintering and forming.Seven distinct physical phenomena are involved in EPM:resistive Joule and induction heating,electrochemical reactions,electroplasticity,electric arcs and electromagnetic heating based on radio and microwave frequencies(mainly used for heating dielectric materials;i.e.,dielectric heating)or on the IR/visible light(IR heating and lasers).
基金partly supported by the Coordenacao de Aperfeicoamento de Pessoal de Nível Superior-Brasil(CAPES)-Finance Code 001,through Grant Nos.BEX 3276/14-7 and BEX 9291/13-0
文摘Processing of materials in the form of ceramics normally involves several steps including calcination at a relatively low temperature for synthesis of the end-product powder and sintering at a high temperature for densification.The work we have been developing introduces a novel approach enabling synthesis plus sintering of materials in a single running experiment by using electric fields,ending with dense ceramics that display grains noticeably finer than in conventional processing.This new paradigm is fully illustrated with experiments conducted on amorphous CaCu3Ti4O12 precursor powder,shown to experience,on heating,crystallization through intermediate phases,followed by chemical reaction leading to synthesis of the end-product powder,plus densification depending on field adjustment.The processing time and furnace temperature are considerably reduced,demonstrating that enhanced synthesis and sintering rates applied under field input.Similar results found in Bi2/3Cu3Ti4O12are also shown.The different factors that may contribute to this unique scenario,including Joule heating,defect generation,and reduction of free energy for nuclei formation promoted by the applied field,are briefly discussed.Overall,the findings we bring here are exclusive as they show an exploitable way that allows rapid processing of materials with good control over particle and grain coarsening.