The nanocomposite magnet based on the exchange coupling effect is a candidate for the new generation of permanent magnets.While the mismatch between the soft and hard magnetic phases introduces a remanence(M_(r))-coer...The nanocomposite magnet based on the exchange coupling effect is a candidate for the new generation of permanent magnets.While the mismatch between the soft and hard magnetic phases introduces a remanence(M_(r))-coercivity(H_(C))trade-off,it prevents a high performance.Here,a gradient multiphase(GMP)heterogeneous structure was constructed to break the M_(r)-H_(C)trade-off in nanocomposite magnets.GMP Sm-Co/FeCo magnet,which comprises multiple Sm-Co hard magnetic phases(1:3,2:7,1:5,1:7,and 2:17)and FeCo soft magnetic phase,achieves both a high H_(C)(6.4 kOe)and a high M_(r)(119 emu/g),yielding a remanent-saturation magnetization ratio(M_(r)/H_(S))of 0.87 and high energy product((BH)_(max))of 25.7 MGOe.In situ magnetic domain observations and micromagnetic simulations revealed that the pinning of multiple hard magnetic phases in the GMP structure forms quasi-magnetic domains composed of multiple magnetic phases.The hard magnetic phases at the edges of the quasi-domains form pinning sites,which provide full pinning action and impede the expansion of the demagnetized domains centered on the soft magnetic phases,leading to superior performance.Further micromagnetic simulations verified that the exchange coupling in GMP Sm-Co/FeCo magnets is improved compared to biphasic(BP)nanocomposite magnets.The strategy of GMP structure can be applied to circumvent performance trade-offs in other heterogeneous functional materials.展开更多
The phase structure and hydrogen storage properties of LaMg 3.70 Ni 1.18 alloy were investigated. The LaMg 3.70 Ni 1.18 alloy consists of main LaMg 2 Ni phase, minor La 2 Mg 17 and LaMg 3 phases. The alloy can be acti...The phase structure and hydrogen storage properties of LaMg 3.70 Ni 1.18 alloy were investigated. The LaMg 3.70 Ni 1.18 alloy consists of main LaMg 2 Ni phase, minor La 2 Mg 17 and LaMg 3 phases. The alloy can be activated in the first hydriding/dehydriding process, and initial LaMg 2 Ni, La 2 Mg 17 , and LaMg 3 phases transfer to LaH 2.34 , Mg, and Mg 2 Ni phases after activation. The reversible hydrogen storage capacity of the LaMg 3.70 Ni 1.18 alloy is 2.47 wt.% at 558 K, which is higher than that of the LaMg 2 Ni alloy. The pressure-composition-temperature （PCT） curves display two hydriding plateaus, corresponding to the formation of MgH 2 and Mg 2 NiH 4 . However, only one dehydriding plateau is observed, owing to the synergetic effect of hydrogen desorption between MgH 2 and Mg 2 NiH 4 . The uptake time for hydrogen content to reach 99% of saturated state is less than 250 s, and 90% hydrogen can be released in 1200 s in the experimental conditions, showing fast kinetics in hydriding and dehydriding. The activation energies of the LaMg 3.70 Ni 1.18 alloy are –51.5 ± 1.1 kJ/mol and –57.0 ± 0.6 kJ/mol for hydriding and dehydriding, respectively. The hydriding/dehydriding kinetics of the LaMg 3.70 Ni 1.18 alloy is better than that of the Mg 2 Ni alloy, owing to the lower activation energy values.展开更多
Matter conductivities are crucial physical properties that directly determine the engineering application value of materials.In reality,the majority of materials are multiphase composites.However,there is currently a ...Matter conductivities are crucial physical properties that directly determine the engineering application value of materials.In reality,the majority of materials are multiphase composites.However,there is currently a lack of theoretical models to accurately predict the conductivities of composite materials.In this study,we develop a unified mixed conductivity(UMC)model,achieving unity in three aspects:(1)a unified description and prediction for different conductivities,including elastic modulus,thermal conductivity,electrical conductivity,magnetic permeability,liquid permeability coefficient,and gas diffusion coefficient;(2)a unified-form governing equation for mixed conductivities of various composite structures,conforming to the Riccati equation;(3)a unified-form composite structure,i.e.,a three-dimensional multiphase interpenetrating cuboid structure,encompassing over a dozen of typical composite structures as its specific cases.The UMC model is applicable for predicting the conductivity across six different types of physical fields and over a dozen different composite structures,providing a broad range of applications.Therefore,the current study deepens our understanding of the conduction phenomena and offers a powerful theoretical tool for predicting the conductivities of composite materials and optimizing their structures,which holds significant scientific and engineering implications.展开更多
In view of the current serious electromagnetic pollution problem,it is urgent to study efficient electromagnetic wave absorbing materials.The construction of multiphase inhomogeneous interfaces is an effective means,e...In view of the current serious electromagnetic pollution problem,it is urgent to study efficient electromagnetic wave absorbing materials.The construction of multiphase inhomogeneous interfaces is an effective means,especially for the fine design of multicomponent materials.In this study,multiphase composites with tunable heterogeneous interfaces were prepared by hydrothermal synthesis,carbon coating and high-temperature annealing processes.Multiple component composites constructed rich heterogeneous interfaces,which exhibited strong interfacial polarization effects and effectively improved the absorption efficiency of electromagnetic wave(EMW).The fine tuning of the heterogeneous interfaces is achieved through component adjustment,which enhances the charge carrier transport efficiency and the polarization loss capability.Ultimately,the multiphase VS_(2)@C@WS_(2)composites obtained excellent EMW absorption performance,with the minimum reflection loss and the maximum effective absorption bandwidth of-66.35 dB and 5.12 GHz,respectively.In this work,the controllable construction of heterogeneous interfaces is achieved through the tuning of components,which provides a valuable method for optimizing the polarization loss.展开更多
This study investigated the atomic-scale deformation mechanism of multiphase CoCrFeNi high-entropy alloys(HEAs)at liquid helium,liquid nitrogen,and room temperatures.A million-atom multiphase HEA was prepared using mo...This study investigated the atomic-scale deformation mechanism of multiphase CoCrFeNi high-entropy alloys(HEAs)at liquid helium,liquid nitrogen,and room temperatures.A million-atom multiphase HEA was prepared using molecular dynamics simulation involving melt and quench processes.The HEA exhibited high-density dislocations and some twins,consistent with experimental observations.Quantitative analysis revealed an inconsistent evolution of the microstructure under tensile deformation.In particular,the elastic and initial plastic stages exhibited an increase in the disordered structure at the expense of the face-centered cubic and hexagonal close-packed structures,followed by a subsequent transformation involving multiple structural rearrangements.Furthermore,through sparse identification,a model depicting microstructural evolution during tension was extracted for the CoCrFeNi HEA at three typical temperatures and three tensile rates.The model highlighted the importance of the body-centered cubic structure in the evolutionary process.展开更多
Microstructure, thermodynamics and electrochemicalproperties of novel RE (NiAlCu)x(x= 4.5, 4.9, 5.6 ) microcrystalline hydrogen-storage alloy powder prepared by gas atomization wasinvestigated. It indicates that alloy...Microstructure, thermodynamics and electrochemicalproperties of novel RE (NiAlCu)x(x= 4.5, 4.9, 5.6 ) microcrystalline hydrogen-storage alloy powder prepared by gas atomization wasinvestigated. It indicates that alloyparticles show relatively regularspherical. Microstructure is composed of the AB5 matrix phase andeutectic double-phase structure withthe AB5 phase and Ni3Al along grainboundaries when x = 5. 6, there is acoexistent structure consisting ofAB5 phase and eutectic doublephase with AB3 and AB phases along grain boundaries at x= 4.5.When x is increased to 4.9, themixed structures are composed ofAB5 and a few AB phases in discontinuous network distribution. Theelectrochemical capacity of alloy is210~300 mAh·g-1, and the activated periods are only 1~3 times.lt seems to be ascribed to the appearance of a great number of freshsurfaces within powder particles resulting from the as-quenched microcrack along the interphase boundaries within particles propagatinggradually in the process of hydrogen-absorption-and dissociation dueto the intrinsic double-phase structure.展开更多
Fe-based compounds with good environmental friendliness and high reversible capacity have attracted considerable attention as anode for lithium-ion batteries.But,similar to other transition metal oxides(TMOs),it is al...Fe-based compounds with good environmental friendliness and high reversible capacity have attracted considerable attention as anode for lithium-ion batteries.But,similar to other transition metal oxides(TMOs),it is also affected by large volume changes and inferior kinetics during redox reactions,resulting in the destruction of the crystal structure and poor electrochemical performance.Here,Fe_(3)O_(4)/C nanospheres anchored on the two-dimensional graphene oxide as precursors are phosphated and sintered to build the multiphasic nanocomposite.XRD results confirmed the multiphasic nanocomposite composed of Fe2O3,Fe_(3)O_(4) and Fe_(3)PO_(7),which will facilitate the Li+diffusion.And the carbonaceous matrix will buffer the volume changes and enhance electron conduction.Consequently,the multiphasic Febased anode delivers a large specific capacity of 1086 mAh/g with a high initial Coulombic efficiency of 87%at 0.1 C.It also has excellent cycling stability and rate property,maintaining a capacity retention of~87%after 300 cycles and a high reversible capacity of 632 mAh/g at 10 C.The proposed multiphasic structure offers a new insight into improving the electrochemical properties of TMO-based anodes for advanced alkali-ion batteries.展开更多
基金supported by National Natural Science Foundation of China(Nos.U23A20549 and 52171184)National Key Research and Development Program of China(No.2023YFB3507600).
文摘The nanocomposite magnet based on the exchange coupling effect is a candidate for the new generation of permanent magnets.While the mismatch between the soft and hard magnetic phases introduces a remanence(M_(r))-coercivity(H_(C))trade-off,it prevents a high performance.Here,a gradient multiphase(GMP)heterogeneous structure was constructed to break the M_(r)-H_(C)trade-off in nanocomposite magnets.GMP Sm-Co/FeCo magnet,which comprises multiple Sm-Co hard magnetic phases(1:3,2:7,1:5,1:7,and 2:17)and FeCo soft magnetic phase,achieves both a high H_(C)(6.4 kOe)and a high M_(r)(119 emu/g),yielding a remanent-saturation magnetization ratio(M_(r)/H_(S))of 0.87 and high energy product((BH)_(max))of 25.7 MGOe.In situ magnetic domain observations and micromagnetic simulations revealed that the pinning of multiple hard magnetic phases in the GMP structure forms quasi-magnetic domains composed of multiple magnetic phases.The hard magnetic phases at the edges of the quasi-domains form pinning sites,which provide full pinning action and impede the expansion of the demagnetized domains centered on the soft magnetic phases,leading to superior performance.Further micromagnetic simulations verified that the exchange coupling in GMP Sm-Co/FeCo magnets is improved compared to biphasic(BP)nanocomposite magnets.The strategy of GMP structure can be applied to circumvent performance trade-offs in other heterogeneous functional materials.
基金supported by the High-Tech Research and Development Program of China (No. 2007AA05Z117)the National Natural Science Foundation of China (Nos. 50971112 and 51001043)+1 种基金the China Post-doctoral Science Foundation Funded Project (20100470990)the Natural Science Foundation of Hebei Province, China (No. E2010001170)
文摘The phase structure and hydrogen storage properties of LaMg 3.70 Ni 1.18 alloy were investigated. The LaMg 3.70 Ni 1.18 alloy consists of main LaMg 2 Ni phase, minor La 2 Mg 17 and LaMg 3 phases. The alloy can be activated in the first hydriding/dehydriding process, and initial LaMg 2 Ni, La 2 Mg 17 , and LaMg 3 phases transfer to LaH 2.34 , Mg, and Mg 2 Ni phases after activation. The reversible hydrogen storage capacity of the LaMg 3.70 Ni 1.18 alloy is 2.47 wt.% at 558 K, which is higher than that of the LaMg 2 Ni alloy. The pressure-composition-temperature （PCT） curves display two hydriding plateaus, corresponding to the formation of MgH 2 and Mg 2 NiH 4 . However, only one dehydriding plateau is observed, owing to the synergetic effect of hydrogen desorption between MgH 2 and Mg 2 NiH 4 . The uptake time for hydrogen content to reach 99% of saturated state is less than 250 s, and 90% hydrogen can be released in 1200 s in the experimental conditions, showing fast kinetics in hydriding and dehydriding. The activation energies of the LaMg 3.70 Ni 1.18 alloy are –51.5 ± 1.1 kJ/mol and –57.0 ± 0.6 kJ/mol for hydriding and dehydriding, respectively. The hydriding/dehydriding kinetics of the LaMg 3.70 Ni 1.18 alloy is better than that of the Mg 2 Ni alloy, owing to the lower activation energy values.
基金supported by the National Natural Science Foundation of China(NSFC)(Nos.52322105,52321001,52130002,U22A20114,and 52371084)the Youth Innovation Promotion Association CAS(No.2021192)+1 种基金the IMR Innovation Fund(No.2023-ZD01)the IMR Outstanding Scholar Position(No.E451A804).
文摘Matter conductivities are crucial physical properties that directly determine the engineering application value of materials.In reality,the majority of materials are multiphase composites.However,there is currently a lack of theoretical models to accurately predict the conductivities of composite materials.In this study,we develop a unified mixed conductivity(UMC)model,achieving unity in three aspects:(1)a unified description and prediction for different conductivities,including elastic modulus,thermal conductivity,electrical conductivity,magnetic permeability,liquid permeability coefficient,and gas diffusion coefficient;(2)a unified-form governing equation for mixed conductivities of various composite structures,conforming to the Riccati equation;(3)a unified-form composite structure,i.e.,a three-dimensional multiphase interpenetrating cuboid structure,encompassing over a dozen of typical composite structures as its specific cases.The UMC model is applicable for predicting the conductivity across six different types of physical fields and over a dozen different composite structures,providing a broad range of applications.Therefore,the current study deepens our understanding of the conduction phenomena and offers a powerful theoretical tool for predicting the conductivities of composite materials and optimizing their structures,which holds significant scientific and engineering implications.
基金supported by the National Natural Science Foundation of China(Nos.52377026 and 52301192)Taishan Scholars and Young Experts Program of Shandong Province(No.tsqn202103057)+1 种基金Natural Science Foundation of Shandong Province(Nos.ZR2024ME046 and ZR2024QE313)Postdoctoral Science Foundation of China(No.2024M761554).
文摘In view of the current serious electromagnetic pollution problem,it is urgent to study efficient electromagnetic wave absorbing materials.The construction of multiphase inhomogeneous interfaces is an effective means,especially for the fine design of multicomponent materials.In this study,multiphase composites with tunable heterogeneous interfaces were prepared by hydrothermal synthesis,carbon coating and high-temperature annealing processes.Multiple component composites constructed rich heterogeneous interfaces,which exhibited strong interfacial polarization effects and effectively improved the absorption efficiency of electromagnetic wave(EMW).The fine tuning of the heterogeneous interfaces is achieved through component adjustment,which enhances the charge carrier transport efficiency and the polarization loss capability.Ultimately,the multiphase VS_(2)@C@WS_(2)composites obtained excellent EMW absorption performance,with the minimum reflection loss and the maximum effective absorption bandwidth of-66.35 dB and 5.12 GHz,respectively.In this work,the controllable construction of heterogeneous interfaces is achieved through the tuning of components,which provides a valuable method for optimizing the polarization loss.
基金supported by the National Natural Science Foundation of China(Grant Nos.U23A2065,52071298,and 51971123)the National Science Foundation(Grant Nos.DMR-1611180 and 1809640)。
文摘This study investigated the atomic-scale deformation mechanism of multiphase CoCrFeNi high-entropy alloys(HEAs)at liquid helium,liquid nitrogen,and room temperatures.A million-atom multiphase HEA was prepared using molecular dynamics simulation involving melt and quench processes.The HEA exhibited high-density dislocations and some twins,consistent with experimental observations.Quantitative analysis revealed an inconsistent evolution of the microstructure under tensile deformation.In particular,the elastic and initial plastic stages exhibited an increase in the disordered structure at the expense of the face-centered cubic and hexagonal close-packed structures,followed by a subsequent transformation involving multiple structural rearrangements.Furthermore,through sparse identification,a model depicting microstructural evolution during tension was extracted for the CoCrFeNi HEA at three typical temperatures and three tensile rates.The model highlighted the importance of the body-centered cubic structure in the evolutionary process.
文摘Microstructure, thermodynamics and electrochemicalproperties of novel RE (NiAlCu)x(x= 4.5, 4.9, 5.6 ) microcrystalline hydrogen-storage alloy powder prepared by gas atomization wasinvestigated. It indicates that alloyparticles show relatively regularspherical. Microstructure is composed of the AB5 matrix phase andeutectic double-phase structure withthe AB5 phase and Ni3Al along grainboundaries when x = 5. 6, there is acoexistent structure consisting ofAB5 phase and eutectic doublephase with AB3 and AB phases along grain boundaries at x= 4.5.When x is increased to 4.9, themixed structures are composed ofAB5 and a few AB phases in discontinuous network distribution. Theelectrochemical capacity of alloy is210~300 mAh·g-1, and the activated periods are only 1~3 times.lt seems to be ascribed to the appearance of a great number of freshsurfaces within powder particles resulting from the as-quenched microcrack along the interphase boundaries within particles propagatinggradually in the process of hydrogen-absorption-and dissociation dueto the intrinsic double-phase structure.
基金supported by the National Natural Science Foundation of China(No.51672109)the Independent Cultivation Program of Innovation Team of Ji’nan City(No.2019GXRC011)Hong Kong Scholars Program(No.XJ2018006)。
文摘Fe-based compounds with good environmental friendliness and high reversible capacity have attracted considerable attention as anode for lithium-ion batteries.But,similar to other transition metal oxides(TMOs),it is also affected by large volume changes and inferior kinetics during redox reactions,resulting in the destruction of the crystal structure and poor electrochemical performance.Here,Fe_(3)O_(4)/C nanospheres anchored on the two-dimensional graphene oxide as precursors are phosphated and sintered to build the multiphasic nanocomposite.XRD results confirmed the multiphasic nanocomposite composed of Fe2O3,Fe_(3)O_(4) and Fe_(3)PO_(7),which will facilitate the Li+diffusion.And the carbonaceous matrix will buffer the volume changes and enhance electron conduction.Consequently,the multiphasic Febased anode delivers a large specific capacity of 1086 mAh/g with a high initial Coulombic efficiency of 87%at 0.1 C.It also has excellent cycling stability and rate property,maintaining a capacity retention of~87%after 300 cycles and a high reversible capacity of 632 mAh/g at 10 C.The proposed multiphasic structure offers a new insight into improving the electrochemical properties of TMO-based anodes for advanced alkali-ion batteries.
