Solid-state precipitation is an effective strategy for tuning the mechanical and functional properties of ad-vanced alloys.Structure design and modification necessitate good knowledge of the kinetic evolution of preci...Solid-state precipitation is an effective strategy for tuning the mechanical and functional properties of ad-vanced alloys.Structure design and modification necessitate good knowledge of the kinetic evolution of precipitates during fabrication,which is strongly correlated with defect concentration.For Fe-Ga alloys,giant magnetostriction can be induced by the precipitation of the nanoscale tetragonal L60 phase.By introducing quenched-in vacancies,we significantly enhance the magnetostriction of the aged Fe81Ga19 polycrystalline alloys to~305 ppm,which is close to the level of single crystals.Although vacancies were found to facilitate the generation of the L60 phase,their impact on the precipitation mechanism and kinetics has yet to be revealed.This study combined transmission electron microscopy(TEM)and time-resolved small-angle neutron scattering(SANS)to investigate the precipitation of the L60 phase during the isothermal aging at 350 and 400℃,respectively.The evolution of L60 nanophase in morphology and number density in as-cast(AC)and liquid nitrogen quenched(LN)Fe81Ga19 alloys with aging time were quantitatively compared.Interestingly,the nucleation of the L60 phase proceeds progressively in AC while suddenly in LN specimens,indicating the homogenous to heterogeneous mechanism switching in-duced by concentrated vacancies.Moreover,excess vacancies can change the shape of nanoprecipitates and significantly accelerate the growth and coarsening kinetics.The magnetostrictive coefficient is opti-mized when the size(long-axis)of L60 precipitates lies between 100 and 110Åwith a number density between 3.2-4.3×10-7Å-3.Insight from this study validates the feasibility of achieving high magnetoe-lastic properties through precise manipulation of the nanostructure.展开更多
Developing ductile bulk metallic glasses(BMGs)can benefit from an in-depth understanding of the structure-property relation during plastic deformation.However,endowing BMGs with tensile ductility in BMGs needs to reve...Developing ductile bulk metallic glasses(BMGs)can benefit from an in-depth understanding of the structure-property relation during plastic deformation.However,endowing BMGs with tensile ductility in BMGs needs to reveal the response of critical structure units during deformation.Here,we report the experimental results of an in-situ synchrotron high-energy X-ray study of a Zr-based BMG under uniaxial tension after preprocessing by canning compression of the three-dimensional compressive stress state.It is revealed that the canning-compressed BMG(CC-BMG)sample has better tensile ductility and higher ultimate strength than the as-cast sample,which possesses heterogeneous and loosely packed local struc-tures on medium-range scales.The experimental results revealed two stages of plastic deformation in the CC-BMGs compared with one stage of plastic deformation in the as-cast BMG.Moreover,the shift in the first sharp diffraction peak along the tension direction for the canning-compressed sample is substan-tially more pronounced than that of the as-cast sample.Furthermore,the real-space analysis illustrates a competition mechanism between the 2-atom and 3-atom connection modes on medium-range order during the plastic deformation of the CC-BMG.Additionally,the ordering on the medium-range scale de-creases in the first plastic deformation stage but increases in the second plastic deformation stage.There-fore,a structural crossover phenomenon occurs in the CC-BMG during plastic deformation.Our results demonstrate a structure-property correlation for the CC-BMGs of heterogeneous medium-range ordered structures,which may be beneficial for endowing BMGs with ductility based on medium-range order engineering techniques.展开更多
The conventional Poisson-Nernst-Planck equations do not account for the finite size of ions explicitly.This leads to solutions featuring unrealistically high ionic concentrations in the regions subject to external pot...The conventional Poisson-Nernst-Planck equations do not account for the finite size of ions explicitly.This leads to solutions featuring unrealistically high ionic concentrations in the regions subject to external potentials,in particular,near highly charged surfaces.A modified form of the Poisson-Nernst-Planck equations accounts for steric effects and results in solutions with finite ion concentrations.Here,we evaluate numerical methods for solving the modified Poisson-Nernst-Planck equations by modeling electric field-driven transport of ions through a nanopore.We describe a novel,robust finite element solver that combines the applications of the Newton’s method to the nonlinear Galerkin form of the equations,augmented with stabilization terms to appropriately handle the drift-diffusion processes.To make direct comparison with particle-based simulations possible,our method is specifically designed to produce solutions under periodic boundary conditions and to conserve the number of ions in the solution domain.We test our finite element solver on a set of challenging numerical experiments that include calculations of the ion distribution in a volume confined between two charged plates,calculations of the ionic current though a nanopore subject to an external electric field,and modeling the effect of a DNA molecule on the ion concentration and nanopore current.展开更多
Understanding the behaviour of matter under conditions of extreme temperature,pressure,density and electromagnetic fields has profound effects on our understanding of cosmologic objects and the formation of the univer...Understanding the behaviour of matter under conditions of extreme temperature,pressure,density and electromagnetic fields has profound effects on our understanding of cosmologic objects and the formation of the universe.Lacking direct access to such objects,our interpretation of observed data mainly relies on theoretical models.However,such models,which need to encompass nuclear physics,atomic physics and plasma physics over a huge dynamic range in the dimensions of energy and time,can only provide reliable information if we can benchmark them to experiments under well-defined laboratory conditions.Due to the plethora of effects occurring in this kind of highly excited matter,characterizing isolated dynamics or obtaining direct insight remains challenging.High-density plasmas are turbulent and opaque for radiation below the plasma frequency and allow only near-surface insight into ionization processes with visible wavelengths.Here,the output of a high-harmonic seeded laser-plasma amplifier using eightfold ionized krypton as the gain medium operating at a 32.8 nm wavelength is ptychographically imaged.A complexvalued wavefront is observed in the extreme ultraviolet(XUV)beam with high resolution.Ab initio spatio-temporal Maxwell–Bloch simulations show excellent agreement with the experimental observations,revealing overionization of krypton in the plasma channel due to nonlinear laser-plasma interactions,successfully validating this four-dimensional multiscale model.This constitutes the first experimental observation of the laser ion abundance reshaping a laserplasma amplifier.The presented approach shows the possibility of directly modelling light-plasma interactions in extreme conditions,such as those present during the early times of the universe,with direct experimental verification.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.12275154)the Guangdong Basic and Applied Basic Research Foundation,China(Project No.2021B1515140028)+1 种基金the Youth Innovation Promotion Association,CAS(No.2020010)the National Key Research and Development Program of China,grant number(Nos.2021YFA1600701 and 2021YFB3501201).
文摘Solid-state precipitation is an effective strategy for tuning the mechanical and functional properties of ad-vanced alloys.Structure design and modification necessitate good knowledge of the kinetic evolution of precipitates during fabrication,which is strongly correlated with defect concentration.For Fe-Ga alloys,giant magnetostriction can be induced by the precipitation of the nanoscale tetragonal L60 phase.By introducing quenched-in vacancies,we significantly enhance the magnetostriction of the aged Fe81Ga19 polycrystalline alloys to~305 ppm,which is close to the level of single crystals.Although vacancies were found to facilitate the generation of the L60 phase,their impact on the precipitation mechanism and kinetics has yet to be revealed.This study combined transmission electron microscopy(TEM)and time-resolved small-angle neutron scattering(SANS)to investigate the precipitation of the L60 phase during the isothermal aging at 350 and 400℃,respectively.The evolution of L60 nanophase in morphology and number density in as-cast(AC)and liquid nitrogen quenched(LN)Fe81Ga19 alloys with aging time were quantitatively compared.Interestingly,the nucleation of the L60 phase proceeds progressively in AC while suddenly in LN specimens,indicating the homogenous to heterogeneous mechanism switching in-duced by concentrated vacancies.Moreover,excess vacancies can change the shape of nanoprecipitates and significantly accelerate the growth and coarsening kinetics.The magnetostrictive coefficient is opti-mized when the size(long-axis)of L60 precipitates lies between 100 and 110Åwith a number density between 3.2-4.3×10-7Å-3.Insight from this study validates the feasibility of achieving high magnetoe-lastic properties through precise manipulation of the nanostructure.
基金the National Key R&D Program of China(No.2021YFB3802800)the National Natural Sci-ence Foundation of China(Nos.52222104,12261160364,51871120 and 51520105001)+3 种基金the Natural Science Foundation of Jiangsu Province(No.BK20200019)Si Lan acknowledges the support by Guangdong-Hong Kong-Macao Joint Laboratory for Neutron Scat-tering Science and Technology and Shenzhen Science and Technol-ogy Innovation Commission(No.JCYJ20200109105618137)the resources of the China Spallation Neutron Source located in Dongguan,China,and the Advanced Photon Source,a US Department of Energy(DOE)Office of Science User Facility op-erated for the DOE Office of Science by Argonne National Labora-tory under Contract No.DE-AC02-06CH11357the US DOE Office of Science,Office of Basic Energy Sciences.The neutron scattering experiments carried out at the Spallation Neutron Source were sponsored by the Scientific User Facilities Di-vision,Office of Basic Energy Sciences,U.S.Department of Energy,under Contract No.DE-AC05-00OR22725 with Oak Ridge National Laboratory.
文摘Developing ductile bulk metallic glasses(BMGs)can benefit from an in-depth understanding of the structure-property relation during plastic deformation.However,endowing BMGs with tensile ductility in BMGs needs to reveal the response of critical structure units during deformation.Here,we report the experimental results of an in-situ synchrotron high-energy X-ray study of a Zr-based BMG under uniaxial tension after preprocessing by canning compression of the three-dimensional compressive stress state.It is revealed that the canning-compressed BMG(CC-BMG)sample has better tensile ductility and higher ultimate strength than the as-cast sample,which possesses heterogeneous and loosely packed local struc-tures on medium-range scales.The experimental results revealed two stages of plastic deformation in the CC-BMGs compared with one stage of plastic deformation in the as-cast BMG.Moreover,the shift in the first sharp diffraction peak along the tension direction for the canning-compressed sample is substan-tially more pronounced than that of the as-cast sample.Furthermore,the real-space analysis illustrates a competition mechanism between the 2-atom and 3-atom connection modes on medium-range order during the plastic deformation of the CC-BMG.Additionally,the ordering on the medium-range scale de-creases in the first plastic deformation stage but increases in the second plastic deformation stage.There-fore,a structural crossover phenomenon occurs in the CC-BMG during plastic deformation.Our results demonstrate a structure-property correlation for the CC-BMGs of heterogeneous medium-range ordered structures,which may be beneficial for endowing BMGs with ductility based on medium-range order engineering techniques.
文摘The conventional Poisson-Nernst-Planck equations do not account for the finite size of ions explicitly.This leads to solutions featuring unrealistically high ionic concentrations in the regions subject to external potentials,in particular,near highly charged surfaces.A modified form of the Poisson-Nernst-Planck equations accounts for steric effects and results in solutions with finite ion concentrations.Here,we evaluate numerical methods for solving the modified Poisson-Nernst-Planck equations by modeling electric field-driven transport of ions through a nanopore.We describe a novel,robust finite element solver that combines the applications of the Newton’s method to the nonlinear Galerkin form of the equations,augmented with stabilization terms to appropriately handle the drift-diffusion processes.To make direct comparison with particle-based simulations possible,our method is specifically designed to produce solutions under periodic boundary conditions and to conserve the number of ions in the solution domain.We test our finite element solver on a set of challenging numerical experiments that include calculations of the ion distribution in a volume confined between two charged plates,calculations of the ionic current though a nanopore subject to an external electric field,and modeling the effect of a DNA molecule on the ion concentration and nanopore current.
基金funding from the European Community’s Horizon 2020 research and innovation program under grant agreement n°654148(LASERLAB EUROPE)support from the Max Planck Society(Max Planck Research Group)and the Federal Ministry of Education and Research(BMBF)under“Make our Planet Great Again-German Research Initiative”(Grant No.57427209“QUESTforENERGY”)implemented by DAAD+4 种基金support from the Federal State of Thuringia and the European Social Fund(ESF)Project 2018 FGR 0080BMBF-project 05P19SJFA1 within Verbundprojekt 05P2018(ErUM-FSP T05)support from the European Community’s Horizon 2020 research and innovation program under grant agreement 665207,project VOXELthe Universidad Politecnica de Madrid(UPM),project DERKETA,the Comunidad de Madrid and UPM,linea de actuacion estimulo a la investigacion de jovenes doctores,project CROM and the Spanish Ministerio de Ciencia e Innovacion through a Ramon y Cajal RYC2018-026238-I fellowshipsupported by“Investissements d’Avenir”Labex PALM(ANR-10-LABX-0039-PALM).
文摘Understanding the behaviour of matter under conditions of extreme temperature,pressure,density and electromagnetic fields has profound effects on our understanding of cosmologic objects and the formation of the universe.Lacking direct access to such objects,our interpretation of observed data mainly relies on theoretical models.However,such models,which need to encompass nuclear physics,atomic physics and plasma physics over a huge dynamic range in the dimensions of energy and time,can only provide reliable information if we can benchmark them to experiments under well-defined laboratory conditions.Due to the plethora of effects occurring in this kind of highly excited matter,characterizing isolated dynamics or obtaining direct insight remains challenging.High-density plasmas are turbulent and opaque for radiation below the plasma frequency and allow only near-surface insight into ionization processes with visible wavelengths.Here,the output of a high-harmonic seeded laser-plasma amplifier using eightfold ionized krypton as the gain medium operating at a 32.8 nm wavelength is ptychographically imaged.A complexvalued wavefront is observed in the extreme ultraviolet(XUV)beam with high resolution.Ab initio spatio-temporal Maxwell–Bloch simulations show excellent agreement with the experimental observations,revealing overionization of krypton in the plasma channel due to nonlinear laser-plasma interactions,successfully validating this four-dimensional multiscale model.This constitutes the first experimental observation of the laser ion abundance reshaping a laserplasma amplifier.The presented approach shows the possibility of directly modelling light-plasma interactions in extreme conditions,such as those present during the early times of the universe,with direct experimental verification.
