Dislocations are thought to be the principal mechanism of high ductility of the novel B2 structure intermetallic compounds YAg and YCu.In this paper, the edge dislocation core structures of two primary slip systems 〈...Dislocations are thought to be the principal mechanism of high ductility of the novel B2 structure intermetallic compounds YAg and YCu.In this paper, the edge dislocation core structures of two primary slip systems 〈100〉{010} and 〈100〉{01^-1} for YAg and YCu are presented theoretically within the lattice theory of dislocation.The governing dislocation equation is a nonlinear integro-differential equation and the variational method is applied to solve the equation.Peierls stresses for 〈100〉{010} and 〈100〉{01^-1} slip systems are calculated taking into consideration the contribution of the elastic strain energy.The core width and Peierls stress of a typical transition-metal aluminide NiAl is also reported for the purpose of verification and comparison.The Peierls stress of NiAl obtained here is in agreement with numerical results,which verifies the correctness of the results obtained for YAg and YCu.Peierls stresses of the 〈100〉{01^-1} slip system are smaller than those of 〈100〉{010} for the same intermetallic compounds originating from the smaller unstable stacking fault energy.The obvious high unstable stacking fault energy of NiAl results in a larger Peierls stress than those of YAg and YCu although they have the same B2 structure.The results show that the core structure and Peierls stress depend monotonically on the unstable stacking fault energy.展开更多
The extended core structure of the dissociated edge dislocation in Al, Au, Ag, Cu and Ni is determined within lattice theory of dislocation. The 2D dislocation equation governing the displacements is coupled by the re...The extended core structure of the dissociated edge dislocation in Al, Au, Ag, Cu and Ni is determined within lattice theory of dislocation. The 2D dislocation equation governing the displacements is coupled by the restoring forces that are determined by the parameterization of the generalized stacking fault energies. The Ritz variational method is presented to solve the dislocation equation and the trial solution is constituted by two arctan-type functions with two undetermined parameters. The core widths of partial dislocations are wider than that obtained in generalized Peierls-Nabarro model due to the consideration of discreteness of crystal.展开更多
We give a brief review of the asymptotic theory of slender vortex filaments with emphases on (i) the choices of scalings and small parameters characterizing the physical problem,(ii) the key steps in the formulation o...We give a brief review of the asymptotic theory of slender vortex filaments with emphases on (i) the choices of scalings and small parameters characterizing the physical problem,(ii) the key steps in the formulation of the theory and (iii) the assumptions and/or restrictions on the theory of Callegari and Ting (1978).We present highlights of an extension of the 1978 asymptotic theory:the analyses for core structures with axial variation.Making use of the physical insights gained from the analyses,we present a new derivation of the evolution equations for the core structure.The new one is simpler and straightforward and shows the physics clearly.展开更多
The study of dislocation properties in B2 structure intermetallics NiAl and FeAl is crucial to understand their mechanical behaviors. In this paper, the core structure and Peierls stress of collinear dissociated (111...The study of dislocation properties in B2 structure intermetallics NiAl and FeAl is crucial to understand their mechanical behaviors. In this paper, the core structure and Peierls stress of collinear dissociated (111){110} edge superdislocations in NiAl and FeAl are investigated with the modified P-N dislocation equation. The generalized stacking fault energy curve along (111) direction in {110} slip plane contains two modification factors that can assure the antiphase energy and the unstable stacking fault energy to change independently. The results show that the core width of superpartials decreases with the increasing unstable stacking fault energy, and increases with the increasing antiphase boundary energy. The calculated Peierls stress of (111){ 110) edge superdislocations in NiAl and FeAl are 475 MPa and 3042 MPa, respectively. The values of Peierls stress in NiAl is in accordance in magnitude with the experimental and the molecular statics simulations results.展开更多
In this paper, Fe30Pt70/Fe3O4 core/shell nanoparticles were synthesized by chemical routine and the layered polyethylenimine (PEI)-Fe30Pt70/Fe3O4 structure was constructed by molecule-mediated self-assembly techniqu...In this paper, Fe30Pt70/Fe3O4 core/shell nanoparticles were synthesized by chemical routine and the layered polyethylenimine (PEI)-Fe30Pt70/Fe3O4 structure was constructed by molecule-mediated self-assembly technique. The dimension of core/shell structured nanoparticles was that of 4nm core and 2 nm shell. After annealing under a flow of forming gas (50%Ar2+30%H2) for 1 h at or above 400℃, the iron oxide shell was reduced to Fe and diffused to Pt-rieh core, which leaded to the formation of L1. phase FePt at low temperature. The x-ray diffraction results and magnetic properties measurement showed that the chemical ordering temperature of Fe30Pt70/Fe3O4 core/shell nanoparticles assembly can be reduced to as low as 400℃. The sample annealed at 400℃ showed the eoereivity of 4KOe with the applied field of 1.5T. The core/shell structure was suggested to be an effective way to reduce the ordering temperature obviously.展开更多
LaF_3:Yb^(3 +),Er^(3 +) nanoparticles were successfully synthesized using solvothermal treatment,and LaF_3:Yb^(3 +),Er^(3 +) /SiO_2 core /shell nanoparticles were also prepared with reverse microemulsion technique.The...LaF_3:Yb^(3 +),Er^(3 +) nanoparticles were successfully synthesized using solvothermal treatment,and LaF_3:Yb^(3 +),Er^(3 +) /SiO_2 core /shell nanoparticles were also prepared with reverse microemulsion technique.The crystal structure,morphology and photoluminescence properties of as-prepared core /shell nanoparticles were investigated by X-ray diffraction,transmission electron microscopy and fluorescence spectrophotometer.The results showed that LaF_3:Yb^(3 +),Er^(3 +) nanoparticles are of hexagonal structure and SiO_2 shell is amorphous.The size of LaF_3:Yb^(3 +),Er^(3 +) nanoparticles is 13 nm and the LaF_3:Yb^(3 +),Er^(3 +) /SiO_2 nanoparticles present clearly a core /shell structure with 12 nm shell thickness.The solubility of LaF_3:Yb^(3 +),Er^(3 +) nanocrystals in water and the biocompatibility are both improved by the SiO_2 shell.The upconversion luminescence spectra suggested that the SiO_2 shell has small effect on the upconversion luminescence properties of the LaF_3:Yb^(3 +),Er^(3 +) nanocrystals.The core /shell structure LaF_3:Yb^(3 +),Er^(3 +) /SiO_2 nanoparticles are expected to be used in biological applications.展开更多
This paper presents a high-resolution simulation of a remarkable polar low observed over the Sea of Japan on 21 January 1997 by using a 5-km mesh non-hydrostatic model MRI-NHM (Meteorological Research Institute Non-Hy...This paper presents a high-resolution simulation of a remarkable polar low observed over the Sea of Japan on 21 January 1997 by using a 5-km mesh non-hydrostatic model MRI-NHM (Meteorological Research Institute Non-Hydrostatic Model). A 24-hour simulation starting from 0000 UTC 21 January 1997 successfully reproduced the observed features of the polar low such as the wrapping of western part of an initial E-W orientation vortex, the spiral-shaped bands, the cloud-free 'eye', and the warm core structure at its mature stage. The 'eye' of the simulated polar low was relatively dry, and was associated with a strong downdraft. A thermodynamic budget analysis indicates that the 'warm core' in the 'eye' region was mainly caused by the adiabatic warming associated with the downdraft. The relationship among the condensational diabatic heating, the vertical velocity, the convergence of the moisture flux, and the circulation averaged within a 50 km×50 km square area around the polar low center shows that they form a positive feedback loop, and this loop is not inconsistent with the CISK (Conditional Instability of the Second Kind) mechanism during the developing stage of the polar low.展开更多
This paper presents an analysis of the coupled vibration of asymmetric core structures in tall buildings. The governing equation of free vibration and its corresponding eigenvalue problem, which is a set of equations ...This paper presents an analysis of the coupled vibration of asymmetric core structures in tall buildings. The governing equation of free vibration and its corresponding eigenvalue problem, which is a set of equations for laterally flexural vibrations in two different directions coupled by a warping-St. Venant torsional vibration, are derived. Based on the Calerkin method, a generalized approximate method is developed for the analysis of coupled vibration and thus proposed for determining the natural frequencies and mode shapes of the structure in triply-coupled vibration. The results of the proposed method for the example structure show good agreement with those of the FEM analysis. The proposed method has been shown to provide a simple and rapid, yet accurate, means for coupled vibration analysis of core structures.展开更多
The reaction of molybdenum hexacarbonyl with C6H5CH2OC6H4ONa and Et4NBr in CH3CN at 60 ℃ afforded the di-nuclear Mo(0) compound [Et4N]3[Mo2(CO)6(μ-OC6H4OCH2C6H5)3] 1. 1 crystallizes in monoclinic, space group ...The reaction of molybdenum hexacarbonyl with C6H5CH2OC6H4ONa and Et4NBr in CH3CN at 60 ℃ afforded the di-nuclear Mo(0) compound [Et4N]3[Mo2(CO)6(μ-OC6H4OCH2C6H5)3] 1. 1 crystallizes in monoclinic, space group P21/c with a = 15.359(2), b = 18.378(3), c = 24.952(2) A, β = 102.268(4)°, V = 6882.3(1 6) A^3, Mr = 1348.34, Z = 4, Dc = 1.301 g/cm^3, F(000) = 2832 and μ= 0.424 mm^-1 The final R = 0.0606 and wR = 0.1552 for 9396 observed reflections (I 〉 2σ(I)). I contains a [Mo2O3]^3 core in triangular bi-pyralnidal configuration and each Mo atom adopts a distorted octahedral geometry with three carbon atoms from carbonyls and three ,μ-O atoms from C6H5CH2OC6H4O^- bridging ligands. The Mo…Mo distance is 3.30(8) A, indicating no metalmetal bonding. A formation pathway via forming a di-molybdenum(0) di-bridging OR compound [Mo2(μ-OR)2(CO)8]2 has been figured out and the reaction of Mo(CO)6 with alkoxide has also been discussed.展开更多
Rational construction of highly efficient and cheap bifunctional electrocatalysts to boost both oxygen evolution reaction(OER)and oxygen reduction reaction(ORR)is extremely essential for the wide application of rechar...Rational construction of highly efficient and cheap bifunctional electrocatalysts to boost both oxygen evolution reaction(OER)and oxygen reduction reaction(ORR)is extremely essential for the wide application of rechargeable metal-air battery.In this work,we design a core-shell structural catalyst of CoNi dual-metal embedded in nitrogen doped porous carbon(NPC,CoNi@NPC),which is developed via the pyrolysis of CoNiMOFs,assisting by mesoporous SiO_(2) to effectively inhibit the aggregation of metal sites.Consequently,the asprepared CoNi@NPC manifests good ORR activity with half-wave potential up to 0.77 V.Specifically,the CoNi@NPC gives a very low OER over-potential of merely 101 mV in 6 M KOH along with high stability,outperforming the commercial Pt/C-RuO_(2).Moreover,the home-made zinc air battery with CoNi@NPC air cathode demonstrates excellent stability over long-term charging–discharging test,and delivers the maximum power density of 224 mW cm^(-2).The enhanced high performance of CoNi@NPC bifunctional catalyst for both ORR and OER can be ascribed to its unique core-shell structure and strong synergistic effect between the dual-bimetal active sites and the heteroatom doped carbon.This work opens a new avenue for the rational design of nonprecious metal bifunctional catalysts for rechargeable metal-air battery.展开更多
Rupturing the alumina shell(shell-breaking)is a prerequisite for releasing energy from aluminum powder.Thermal stress overload in a high-temperature environment is an important factor in the rupture of the alumina she...Rupturing the alumina shell(shell-breaking)is a prerequisite for releasing energy from aluminum powder.Thermal stress overload in a high-temperature environment is an important factor in the rupture of the alumina shell.COMSOL Multiphysics was used to simulate and analyze the shell-breaking response of micron-scale aluminum particles with different particle sizes at 650℃in vacuum.The simulation results show that the thermal stability time and shell-breaking response time of 10μm–100μm aluminum particles are 0.15μs–11.44μs and 0.08μs–3.94μs,respectively.They also reveal the direct causes of shell breaking for aluminum particles with different particle sizes.When the particle size is less than 80μm,the shell-breaking response is a direct result of compressive stress overload.When the particle size is between80μm and 100μm,the shell-breaking response is a direct result of tensile stress overload.This article provides useful guidance for research into the energy release of aluminum powder.展开更多
We have carried out computer atomistic simulations, based on an efficient density functional based tight binding method, to investigate the core configurations of the 60°basal dislocation in GaN wurtzite. Our ene...We have carried out computer atomistic simulations, based on an efficient density functional based tight binding method, to investigate the core configurations of the 60°basal dislocation in GaN wurtzite. Our energetic calculations, on the undissociated dislocation, demonstrate that the glide configuration with N polarity is the most energetically favorable over both the glide and the shuffle sets.展开更多
Crystalline Fe/MnO@C core–shell nanocapsules inlaid in porous amorphous carbon matrix(FMCA)was synthesized successfully with a novel confinement strategy.The heterogeneous Fe/MnO nanocrystals are with approximate sin...Crystalline Fe/MnO@C core–shell nanocapsules inlaid in porous amorphous carbon matrix(FMCA)was synthesized successfully with a novel confinement strategy.The heterogeneous Fe/MnO nanocrystals are with approximate single-domain size which gives rise to natural resonance in 2–18 GHz.The addition of MnO2 confines degree of graphitization catalyzed by iron and contributes to the formation of amorphous carbon.The heterogeneous materials composed of crystalline–amorphous structures disperse evenly and its density is significantly reduced on account of porous properties.Meanwhile,adjustable dielectric loss is achieved by interrupting Fe core aggregation and stacking graphene conductive network.The dielectric loss synergistically with magnetic loss endows the FMCA enhanced absorption.The optimal reflection loss(RL)is up to−45 dB,and the effective bandwidth(RL<−10 dB)is 5.0 GHz with 2.0 mm thickness.The proposed confinement strategy not only lays the foundation for designing high-performance microwave absorber,but also offers a general duty synthesis method for heterogeneous crystalline–amorphous composites with tunable composition in other fields.展开更多
Electrode material based on a novel core–shell structure consisting of NiCoS(NCS) solid fiber core and Mn S(MS) sheet shell(NCS@MS) in situ grown on carbon cloth(CC) has been successfully prepared by a simple...Electrode material based on a novel core–shell structure consisting of NiCoS(NCS) solid fiber core and Mn S(MS) sheet shell(NCS@MS) in situ grown on carbon cloth(CC) has been successfully prepared by a simple sulfurization-assisted hydrothermal method for high performance supercapacitor. The synthesized NiCoS@Mn S/CC electrode shows high capacitance of 1908.3 F gat a current density of 0.5 A gwhich is higher than those of NiCoSand Mn S at the same current density. A flexible all-solid-state asymmetric supercapacitor(ASC) is constructed by using NiCoS@Mn S/CC as positive electrode, active carbon/CC as negative electrode and KOH/poly(vinyl alcohol)(PVA) as electrolyte. The optimized ASC shows a maximum energy density of 23.3 Wh kgat 1 A g, a maximum power density of about7.5 kw kgat 10 A gand remarkable cycling stability. After 9000 cycles, the ASC still exhibited67.8% retention rate and largely unchanged charge/discharge curves. The excellent electrochemical properties are resulted from the novel core–shell structure of the NiCoS@Mn S/CC electrode, which possesses both high surface area for Faraday redox reaction and superior kinetics of charge transport. The NiCoS@Mn S/CC electrode shows a promising potential for energy storage applications in the future.展开更多
Advanced biomaterial-based strategies for treatment of peripheral nerve injury require precise control over both topological and biological cues for facilitating rapid and directed nerve regeneration.As a highly bioac...Advanced biomaterial-based strategies for treatment of peripheral nerve injury require precise control over both topological and biological cues for facilitating rapid and directed nerve regeneration.As a highly bioactive and tissue-specifc natural material,decellularized extracellular matrix(dECM)derived from peripheral nerves(decellularized nerve matrix,DNM)has drawn increasing attention in the feld of regenerative medicine,due to its outstanding capabilities in facilitating neurite outgrowth and remyelination.To induce and maintain sufcient topological guidance,electrospinning was conducted for fabrication of axially aligned nanofbers consisting of DNM and poly(ε-caprolactone)(PCL).Core–shell structured fbers were prepared by coaxial electrospinning using DNM as the shell and PCL as the core.Compared to the aligned electrospun fbers using preblended DNM/PCL,the core–shell structured fbers exhibited lower tensile strength,faster degradation,but considerable toughness for nerve guidance conduit preparation and relatively intact fbrous structure after long-term degradation.More importantly,the full DNM surface coverage of the aligned core–shell fbers efectively promoted axonal extension and Schwann cells migration.The DNM contents further triggered neurite bundling and myelin formation toward nerve fber maturation and functionalization.Herein,we not only pursue a multi-functional scafold design for nerve regeneration,a detailed comparison between core–shell structured and preblended electrospinning of DNM/PCL composites was also provided as an applicable paradigm for advanced tissue-engineered strategies using dECM-based biomaterials.展开更多
Elemental state matter-heteroatom-doped carbon composites are of great importance for the development of anode in lithium ion batteries(LIBs).In this article,metal–organic frameworks(MOFs)are adopted as precursor to ...Elemental state matter-heteroatom-doped carbon composites are of great importance for the development of anode in lithium ion batteries(LIBs).In this article,metal–organic frameworks(MOFs)are adopted as precursor to prepare Co composites via metallurgical pyrolysis under controllable conditions.The obtained nitrogen-doped porous carbon-Co nanocomposite possesses core–shell structure(Co@C–N).Co@C–N exhibits the best Li storage performances as anode active matter.After the 200th cycles at current density of 0.2 A g^(-1),a reversible capacity of 870 mAh g^(-1)is retained.A reversible capacity of 275 mAh g^(-1)still maintains with 5 A g^(-1).Co@C–N presents a high reversible capacity with excellent cycle stability.Considering the corresponding experimental and theoretical results,the Co0-based N-doped porous carbon composite is proposed to work as LIBs anode matter.These results provide a new design idea for electrode matters of metallic ion battery,and demonstrate that MOFs pyrolysis is an effective method for the construction of elemental state anode materials.展开更多
In this paper,we use microwave reduction strategy to synthesize a new bi-functional sulfur host material at the service of cathode substrate for lithium-sulfur batteries(LSBs),the composite is made of hierarchical por...In this paper,we use microwave reduction strategy to synthesize a new bi-functional sulfur host material at the service of cathode substrate for lithium-sulfur batteries(LSBs),the composite is made of hierarchical porous carbon foam supported carbon-encapsulated chromium carbide nano-particles(Cr_(3)C_(2)@C/HPCF),in which the well-distributed conductive Cr_(3)C_(2) nano-particles can act as powerful chemical adsorbent and are effective in restraining the shuttle effect of lithium polysulfides(LiPSs).Test results show that the Cr_(3)C_(2)@C/HPCF based sulfur electrodes with 75 wt.%of sulfur exhibit a high initial discharging capacity of 1,321.1 mAh·g^(−1) at 0.1 C(3.5 mg·cm^(−2)),and a reversible capacity can still maintain stability at 1,002.1 mAh·g^(−1) after 150 cycles.Even increasing the areal sulfur loading to 4 mg·cm^(−2),the electrodes can still deliver an initial discharging capacity of 948.0 mAh·g^(−1) at 0.5 C with ultra-slow capacity decay rate of 0.075%per cycle during 500 cycles.Furthermore,the adsorption energy between the Cr_(3)C_(2) surface and LiPSs as well as theoretic analysis based on first-principles is also investigated.展开更多
Sub-micron sized phenolic epoxy resin waterborne particles were prepared by phase inversion emulsification. Micro-phase separation occurred during the curing process at high temperature. The as-prepared samples posses...Sub-micron sized phenolic epoxy resin waterborne particles were prepared by phase inversion emulsification. Micro-phase separation occurred during the curing process at high temperature. The as-prepared samples possessed one glass transition temperature (Tg) and two exothermal processes during DSC heating scannings. After being thermally treated above the exothermal peak temperature, they possessed two glass transition temperatures with the disappearance of exothermal peaks, whilst a core/shell structure was formed. This was likely related with the outward diffusion of reactive oligomers to the outer layer of particles.展开更多
Conversion-type anode materials with a high charge storage capability generally su er from large volume expansion, poor electron conductivity, and sluggish metal ion transport kinetics. The electrode material describe...Conversion-type anode materials with a high charge storage capability generally su er from large volume expansion, poor electron conductivity, and sluggish metal ion transport kinetics. The electrode material described in this paper, namely cobalt sulphide nanoparticles encapsulated in carbon cages(Co9S8@NC), can circumvent these problems. This electrode material exhibited a reversible sodium-ion storage capacity of 705 mAh g^-1 at 100 mA g^-1 with an extraordinary rate capability and good cycling stability. Mechanistic study using the in situ transmission electron microscope technique revealed that the volumetric expansion of the Co9S8 nanoparticles is bu ered by the carbon cages, enabling a stable electrode–electrolyte interface. In addition, the carbon shell with high-content doped nitrogen significantly enhances the electron conductivity of the Co9S8@NC electrode material and provides doping-induced active sites to accommodate sodium ions. By integrating the Co9S8@NC as negative electrode with a cellulose-derived porous hard carbon/graphene oxide composite as positive electrode and 1 M NaPF6 in diglyme as the electrolyte, the sodium-ion capacitor full cell can achieve energy densities of 101.4 and 45.8 Wh kg^-1 at power densities of 200 and 10,000 W kg^-1, respectively.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No 10774196)Science Foundation Project of CQ Chongqing Science & Technology Commission (CSTC) (Grant No 2006BB4156)Chongqing University Postgraduates’Science and Innovation Fund (Grant No 200707A1A0030240)
文摘Dislocations are thought to be the principal mechanism of high ductility of the novel B2 structure intermetallic compounds YAg and YCu.In this paper, the edge dislocation core structures of two primary slip systems 〈100〉{010} and 〈100〉{01^-1} for YAg and YCu are presented theoretically within the lattice theory of dislocation.The governing dislocation equation is a nonlinear integro-differential equation and the variational method is applied to solve the equation.Peierls stresses for 〈100〉{010} and 〈100〉{01^-1} slip systems are calculated taking into consideration the contribution of the elastic strain energy.The core width and Peierls stress of a typical transition-metal aluminide NiAl is also reported for the purpose of verification and comparison.The Peierls stress of NiAl obtained here is in agreement with numerical results,which verifies the correctness of the results obtained for YAg and YCu.Peierls stresses of the 〈100〉{01^-1} slip system are smaller than those of 〈100〉{010} for the same intermetallic compounds originating from the smaller unstable stacking fault energy.The obvious high unstable stacking fault energy of NiAl results in a larger Peierls stress than those of YAg and YCu although they have the same B2 structure.The results show that the core structure and Peierls stress depend monotonically on the unstable stacking fault energy.
基金supported by the National Natural Science Foundation of China (No.10774196)the Science Founda-tion Project of CQ CSTC (No.2006BB4156)Chongqing University Postgraduates’Science and Innovation Fund(No.200707A1A0030240)
文摘The extended core structure of the dissociated edge dislocation in Al, Au, Ag, Cu and Ni is determined within lattice theory of dislocation. The 2D dislocation equation governing the displacements is coupled by the restoring forces that are determined by the parameterization of the generalized stacking fault energies. The Ritz variational method is presented to solve the dislocation equation and the trial solution is constituted by two arctan-type functions with two undetermined parameters. The core widths of partial dislocations are wider than that obtained in generalized Peierls-Nabarro model due to the consideration of discreteness of crystal.
文摘We give a brief review of the asymptotic theory of slender vortex filaments with emphases on (i) the choices of scalings and small parameters characterizing the physical problem,(ii) the key steps in the formulation of the theory and (iii) the assumptions and/or restrictions on the theory of Callegari and Ting (1978).We present highlights of an extension of the 1978 asymptotic theory:the analyses for core structures with axial variation.Making use of the physical insights gained from the analyses,we present a new derivation of the evolution equations for the core structure.The new one is simpler and straightforward and shows the physics clearly.
基金supported by the Fundamental Research Funds for the Central Universities(No.CDJZR10100019).
文摘The study of dislocation properties in B2 structure intermetallics NiAl and FeAl is crucial to understand their mechanical behaviors. In this paper, the core structure and Peierls stress of collinear dissociated (111){110} edge superdislocations in NiAl and FeAl are investigated with the modified P-N dislocation equation. The generalized stacking fault energy curve along (111) direction in {110} slip plane contains two modification factors that can assure the antiphase energy and the unstable stacking fault energy to change independently. The results show that the core width of superpartials decreases with the increasing unstable stacking fault energy, and increases with the increasing antiphase boundary energy. The calculated Peierls stress of (111){ 110) edge superdislocations in NiAl and FeAl are 475 MPa and 3042 MPa, respectively. The values of Peierls stress in NiAl is in accordance in magnitude with the experimental and the molecular statics simulations results.
基金Project supported by the National Natural Science Foundation of China (Grant No 50641006) and the Science Foundation of Education Commission of Beijing, China.
文摘In this paper, Fe30Pt70/Fe3O4 core/shell nanoparticles were synthesized by chemical routine and the layered polyethylenimine (PEI)-Fe30Pt70/Fe3O4 structure was constructed by molecule-mediated self-assembly technique. The dimension of core/shell structured nanoparticles was that of 4nm core and 2 nm shell. After annealing under a flow of forming gas (50%Ar2+30%H2) for 1 h at or above 400℃, the iron oxide shell was reduced to Fe and diffused to Pt-rieh core, which leaded to the formation of L1. phase FePt at low temperature. The x-ray diffraction results and magnetic properties measurement showed that the chemical ordering temperature of Fe30Pt70/Fe3O4 core/shell nanoparticles assembly can be reduced to as low as 400℃. The sample annealed at 400℃ showed the eoereivity of 4KOe with the applied field of 1.5T. The core/shell structure was suggested to be an effective way to reduce the ordering temperature obviously.
文摘LaF_3:Yb^(3 +),Er^(3 +) nanoparticles were successfully synthesized using solvothermal treatment,and LaF_3:Yb^(3 +),Er^(3 +) /SiO_2 core /shell nanoparticles were also prepared with reverse microemulsion technique.The crystal structure,morphology and photoluminescence properties of as-prepared core /shell nanoparticles were investigated by X-ray diffraction,transmission electron microscopy and fluorescence spectrophotometer.The results showed that LaF_3:Yb^(3 +),Er^(3 +) nanoparticles are of hexagonal structure and SiO_2 shell is amorphous.The size of LaF_3:Yb^(3 +),Er^(3 +) nanoparticles is 13 nm and the LaF_3:Yb^(3 +),Er^(3 +) /SiO_2 nanoparticles present clearly a core /shell structure with 12 nm shell thickness.The solubility of LaF_3:Yb^(3 +),Er^(3 +) nanocrystals in water and the biocompatibility are both improved by the SiO_2 shell.The upconversion luminescence spectra suggested that the SiO_2 shell has small effect on the upconversion luminescence properties of the LaF_3:Yb^(3 +),Er^(3 +) nanocrystals.The core /shell structure LaF_3:Yb^(3 +),Er^(3 +) /SiO_2 nanoparticles are expected to be used in biological applications.
基金The first author was partly supported by the Chinese Ministry of Education,and the Japanese Ministry of Education,Science and Culture through their scholarship exchange programsthe National Natural Science Foundation of China under the Grant Nos.40275033 and 40240420564This work was also supported by the State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry(LAPC)of the Institute of Atmospheric Physics of the Chinese Academy of Sciences under Grant No.LAPC-KF-2003-10.
文摘This paper presents a high-resolution simulation of a remarkable polar low observed over the Sea of Japan on 21 January 1997 by using a 5-km mesh non-hydrostatic model MRI-NHM (Meteorological Research Institute Non-Hydrostatic Model). A 24-hour simulation starting from 0000 UTC 21 January 1997 successfully reproduced the observed features of the polar low such as the wrapping of western part of an initial E-W orientation vortex, the spiral-shaped bands, the cloud-free 'eye', and the warm core structure at its mature stage. The 'eye' of the simulated polar low was relatively dry, and was associated with a strong downdraft. A thermodynamic budget analysis indicates that the 'warm core' in the 'eye' region was mainly caused by the adiabatic warming associated with the downdraft. The relationship among the condensational diabatic heating, the vertical velocity, the convergence of the moisture flux, and the circulation averaged within a 50 km×50 km square area around the polar low center shows that they form a positive feedback loop, and this loop is not inconsistent with the CISK (Conditional Instability of the Second Kind) mechanism during the developing stage of the polar low.
文摘This paper presents an analysis of the coupled vibration of asymmetric core structures in tall buildings. The governing equation of free vibration and its corresponding eigenvalue problem, which is a set of equations for laterally flexural vibrations in two different directions coupled by a warping-St. Venant torsional vibration, are derived. Based on the Calerkin method, a generalized approximate method is developed for the analysis of coupled vibration and thus proposed for determining the natural frequencies and mode shapes of the structure in triply-coupled vibration. The results of the proposed method for the example structure show good agreement with those of the FEM analysis. The proposed method has been shown to provide a simple and rapid, yet accurate, means for coupled vibration analysis of core structures.
基金This research was supported by NNSFC (No. 90203017 29733090), NBRP (2004CB7201005) and SKLSC
文摘The reaction of molybdenum hexacarbonyl with C6H5CH2OC6H4ONa and Et4NBr in CH3CN at 60 ℃ afforded the di-nuclear Mo(0) compound [Et4N]3[Mo2(CO)6(μ-OC6H4OCH2C6H5)3] 1. 1 crystallizes in monoclinic, space group P21/c with a = 15.359(2), b = 18.378(3), c = 24.952(2) A, β = 102.268(4)°, V = 6882.3(1 6) A^3, Mr = 1348.34, Z = 4, Dc = 1.301 g/cm^3, F(000) = 2832 and μ= 0.424 mm^-1 The final R = 0.0606 and wR = 0.1552 for 9396 observed reflections (I 〉 2σ(I)). I contains a [Mo2O3]^3 core in triangular bi-pyralnidal configuration and each Mo atom adopts a distorted octahedral geometry with three carbon atoms from carbonyls and three ,μ-O atoms from C6H5CH2OC6H4O^- bridging ligands. The Mo…Mo distance is 3.30(8) A, indicating no metalmetal bonding. A formation pathway via forming a di-molybdenum(0) di-bridging OR compound [Mo2(μ-OR)2(CO)8]2 has been figured out and the reaction of Mo(CO)6 with alkoxide has also been discussed.
基金supported by National Natural Science Foundation of China(21972017)the“Scientific and Technical Innovation Action Plan”Hong Kong,MacaoTaiwan Science&Technology Cooperation Project of Shanghai Science and Technology Committee(19160760600).
文摘Rational construction of highly efficient and cheap bifunctional electrocatalysts to boost both oxygen evolution reaction(OER)and oxygen reduction reaction(ORR)is extremely essential for the wide application of rechargeable metal-air battery.In this work,we design a core-shell structural catalyst of CoNi dual-metal embedded in nitrogen doped porous carbon(NPC,CoNi@NPC),which is developed via the pyrolysis of CoNiMOFs,assisting by mesoporous SiO_(2) to effectively inhibit the aggregation of metal sites.Consequently,the asprepared CoNi@NPC manifests good ORR activity with half-wave potential up to 0.77 V.Specifically,the CoNi@NPC gives a very low OER over-potential of merely 101 mV in 6 M KOH along with high stability,outperforming the commercial Pt/C-RuO_(2).Moreover,the home-made zinc air battery with CoNi@NPC air cathode demonstrates excellent stability over long-term charging–discharging test,and delivers the maximum power density of 224 mW cm^(-2).The enhanced high performance of CoNi@NPC bifunctional catalyst for both ORR and OER can be ascribed to its unique core-shell structure and strong synergistic effect between the dual-bimetal active sites and the heteroatom doped carbon.This work opens a new avenue for the rational design of nonprecious metal bifunctional catalysts for rechargeable metal-air battery.
基金the National Natural Science Foundation of China(Grant No.11802160)。
文摘Rupturing the alumina shell(shell-breaking)is a prerequisite for releasing energy from aluminum powder.Thermal stress overload in a high-temperature environment is an important factor in the rupture of the alumina shell.COMSOL Multiphysics was used to simulate and analyze the shell-breaking response of micron-scale aluminum particles with different particle sizes at 650℃in vacuum.The simulation results show that the thermal stability time and shell-breaking response time of 10μm–100μm aluminum particles are 0.15μs–11.44μs and 0.08μs–3.94μs,respectively.They also reveal the direct causes of shell breaking for aluminum particles with different particle sizes.When the particle size is less than 80μm,the shell-breaking response is a direct result of compressive stress overload.When the particle size is between80μm and 100μm,the shell-breaking response is a direct result of tensile stress overload.This article provides useful guidance for research into the energy release of aluminum powder.
基金financial support from Abderahmane Mira university of Bejaia.
文摘We have carried out computer atomistic simulations, based on an efficient density functional based tight binding method, to investigate the core configurations of the 60°basal dislocation in GaN wurtzite. Our energetic calculations, on the undissociated dislocation, demonstrate that the glide configuration with N polarity is the most energetically favorable over both the glide and the shuffle sets.
基金Supported by Program for the National Natural Science Foundation of China (Nos. 51577021 and U1704253)the Fundamental Research Funds for the Central Universities (DUT17GF107)
文摘Crystalline Fe/MnO@C core–shell nanocapsules inlaid in porous amorphous carbon matrix(FMCA)was synthesized successfully with a novel confinement strategy.The heterogeneous Fe/MnO nanocrystals are with approximate single-domain size which gives rise to natural resonance in 2–18 GHz.The addition of MnO2 confines degree of graphitization catalyzed by iron and contributes to the formation of amorphous carbon.The heterogeneous materials composed of crystalline–amorphous structures disperse evenly and its density is significantly reduced on account of porous properties.Meanwhile,adjustable dielectric loss is achieved by interrupting Fe core aggregation and stacking graphene conductive network.The dielectric loss synergistically with magnetic loss endows the FMCA enhanced absorption.The optimal reflection loss(RL)is up to−45 dB,and the effective bandwidth(RL<−10 dB)is 5.0 GHz with 2.0 mm thickness.The proposed confinement strategy not only lays the foundation for designing high-performance microwave absorber,but also offers a general duty synthesis method for heterogeneous crystalline–amorphous composites with tunable composition in other fields.
基金supported by the Grant-in-Aid for Scientific Research (KAKENHI) program, Japan (C, Grant Number 15K05597)Takahashi Industrial and Economic Research Foundation (Takahashi Grant Number 06-003-154)
文摘Electrode material based on a novel core–shell structure consisting of NiCoS(NCS) solid fiber core and Mn S(MS) sheet shell(NCS@MS) in situ grown on carbon cloth(CC) has been successfully prepared by a simple sulfurization-assisted hydrothermal method for high performance supercapacitor. The synthesized NiCoS@Mn S/CC electrode shows high capacitance of 1908.3 F gat a current density of 0.5 A gwhich is higher than those of NiCoSand Mn S at the same current density. A flexible all-solid-state asymmetric supercapacitor(ASC) is constructed by using NiCoS@Mn S/CC as positive electrode, active carbon/CC as negative electrode and KOH/poly(vinyl alcohol)(PVA) as electrolyte. The optimized ASC shows a maximum energy density of 23.3 Wh kgat 1 A g, a maximum power density of about7.5 kw kgat 10 A gand remarkable cycling stability. After 9000 cycles, the ASC still exhibited67.8% retention rate and largely unchanged charge/discharge curves. The excellent electrochemical properties are resulted from the novel core–shell structure of the NiCoS@Mn S/CC electrode, which possesses both high surface area for Faraday redox reaction and superior kinetics of charge transport. The NiCoS@Mn S/CC electrode shows a promising potential for energy storage applications in the future.
基金The authors thank Dr.Hong Zhai for her technical support in material characterizationsThis work was funded by National Key R&D Program of China(No.2018YFC1106001)+2 种基金National Natural Science Foundation of China(51903255 and 52073314)The Key Areas Research and Development Program of Guangdong(2020B1111150003 and 2019B020235001)Science and Technology Program of Guangzhou City(201904010364).
文摘Advanced biomaterial-based strategies for treatment of peripheral nerve injury require precise control over both topological and biological cues for facilitating rapid and directed nerve regeneration.As a highly bioactive and tissue-specifc natural material,decellularized extracellular matrix(dECM)derived from peripheral nerves(decellularized nerve matrix,DNM)has drawn increasing attention in the feld of regenerative medicine,due to its outstanding capabilities in facilitating neurite outgrowth and remyelination.To induce and maintain sufcient topological guidance,electrospinning was conducted for fabrication of axially aligned nanofbers consisting of DNM and poly(ε-caprolactone)(PCL).Core–shell structured fbers were prepared by coaxial electrospinning using DNM as the shell and PCL as the core.Compared to the aligned electrospun fbers using preblended DNM/PCL,the core–shell structured fbers exhibited lower tensile strength,faster degradation,but considerable toughness for nerve guidance conduit preparation and relatively intact fbrous structure after long-term degradation.More importantly,the full DNM surface coverage of the aligned core–shell fbers efectively promoted axonal extension and Schwann cells migration.The DNM contents further triggered neurite bundling and myelin formation toward nerve fber maturation and functionalization.Herein,we not only pursue a multi-functional scafold design for nerve regeneration,a detailed comparison between core–shell structured and preblended electrospinning of DNM/PCL composites was also provided as an applicable paradigm for advanced tissue-engineered strategies using dECM-based biomaterials.
基金the National Natural Science Foundation of China(Nos.31530010 and 21401168)the Special Project of Guangdong Province to Introduce Innovation and Entrepreneurship Team(No.2016ZT06N467)is acknowledged.
文摘Elemental state matter-heteroatom-doped carbon composites are of great importance for the development of anode in lithium ion batteries(LIBs).In this article,metal–organic frameworks(MOFs)are adopted as precursor to prepare Co composites via metallurgical pyrolysis under controllable conditions.The obtained nitrogen-doped porous carbon-Co nanocomposite possesses core–shell structure(Co@C–N).Co@C–N exhibits the best Li storage performances as anode active matter.After the 200th cycles at current density of 0.2 A g^(-1),a reversible capacity of 870 mAh g^(-1)is retained.A reversible capacity of 275 mAh g^(-1)still maintains with 5 A g^(-1).Co@C–N presents a high reversible capacity with excellent cycle stability.Considering the corresponding experimental and theoretical results,the Co0-based N-doped porous carbon composite is proposed to work as LIBs anode matter.These results provide a new design idea for electrode matters of metallic ion battery,and demonstrate that MOFs pyrolysis is an effective method for the construction of elemental state anode materials.
基金The authors appreciate support by the Natural Science Foundation of Anhui Province(No.1908085ME147)Projects of International Cooperation and Exchanges in Anhui Provincial Key Project of Research(No.202004b11020010)+2 种基金Shenzhen Basic Research Program(Nos.JCYJ20190808141611189,JCYJ20170818100134570,and JCYJ20160422091418366)Basic and applied basic research fund of Guangdong Province(No.2020A1515011018)we are grateful to Instrumental Analysis Center of Shenzhen University(Xili Campus)for the help with TEM,and thanks for technical support by Ceshigo Research Service Agency(www.ceshigo.com)for XAS,ACSTEM and DFT/MD.
文摘In this paper,we use microwave reduction strategy to synthesize a new bi-functional sulfur host material at the service of cathode substrate for lithium-sulfur batteries(LSBs),the composite is made of hierarchical porous carbon foam supported carbon-encapsulated chromium carbide nano-particles(Cr_(3)C_(2)@C/HPCF),in which the well-distributed conductive Cr_(3)C_(2) nano-particles can act as powerful chemical adsorbent and are effective in restraining the shuttle effect of lithium polysulfides(LiPSs).Test results show that the Cr_(3)C_(2)@C/HPCF based sulfur electrodes with 75 wt.%of sulfur exhibit a high initial discharging capacity of 1,321.1 mAh·g^(−1) at 0.1 C(3.5 mg·cm^(−2)),and a reversible capacity can still maintain stability at 1,002.1 mAh·g^(−1) after 150 cycles.Even increasing the areal sulfur loading to 4 mg·cm^(−2),the electrodes can still deliver an initial discharging capacity of 948.0 mAh·g^(−1) at 0.5 C with ultra-slow capacity decay rate of 0.075%per cycle during 500 cycles.Furthermore,the adsorption energy between the Cr_(3)C_(2) surface and LiPSs as well as theoretic analysis based on first-principles is also investigated.
基金This work was financially supported by the National Natural Science Foundation of China(No.20104008).
文摘Sub-micron sized phenolic epoxy resin waterborne particles were prepared by phase inversion emulsification. Micro-phase separation occurred during the curing process at high temperature. The as-prepared samples possessed one glass transition temperature (Tg) and two exothermal processes during DSC heating scannings. After being thermally treated above the exothermal peak temperature, they possessed two glass transition temperatures with the disappearance of exothermal peaks, whilst a core/shell structure was formed. This was likely related with the outward diffusion of reactive oligomers to the outer layer of particles.
基金supported by The Australian Research Council(ARC)under project FL170100101The University of Queensland for o ering UQI Scholarship
文摘Conversion-type anode materials with a high charge storage capability generally su er from large volume expansion, poor electron conductivity, and sluggish metal ion transport kinetics. The electrode material described in this paper, namely cobalt sulphide nanoparticles encapsulated in carbon cages(Co9S8@NC), can circumvent these problems. This electrode material exhibited a reversible sodium-ion storage capacity of 705 mAh g^-1 at 100 mA g^-1 with an extraordinary rate capability and good cycling stability. Mechanistic study using the in situ transmission electron microscope technique revealed that the volumetric expansion of the Co9S8 nanoparticles is bu ered by the carbon cages, enabling a stable electrode–electrolyte interface. In addition, the carbon shell with high-content doped nitrogen significantly enhances the electron conductivity of the Co9S8@NC electrode material and provides doping-induced active sites to accommodate sodium ions. By integrating the Co9S8@NC as negative electrode with a cellulose-derived porous hard carbon/graphene oxide composite as positive electrode and 1 M NaPF6 in diglyme as the electrolyte, the sodium-ion capacitor full cell can achieve energy densities of 101.4 and 45.8 Wh kg^-1 at power densities of 200 and 10,000 W kg^-1, respectively.