Refractory alloys such as tungsten and molybdenum based alloys with high strength,thermal/electrical conductivity,low coefficient of thermal expansion and excellent creep resistances are highly desirable for applicati...Refractory alloys such as tungsten and molybdenum based alloys with high strength,thermal/electrical conductivity,low coefficient of thermal expansion and excellent creep resistances are highly desirable for applications in nuclear facilities,critical components in aerospace and defense components.However,the serious embrittlement limits the engineering usability of some refractory alloys.A lot of research results indicate that the performances of refractory alloys are closely related to the physical/chemical status,such as the interface dimension,interface type,interface composition of their grain boundaries(GBs),phase boundaries(PBs)and other interface features.This paper reviewed the recent progress of simulations and experiments on interface design strategies that achieve high performance refractory alloys.These strategies include GB interface purifying/strengthening,PB interface strengthening and PB/GB synergistic strengthening.Great details are provided on the design/fabrication strategy such as GB interface controlling,PB interface controlling and synergistic control of multi-scaled interfaces.The corresponding performances such as the mechanical property,thermal conductivity,thermal load resistance,thermal stability,irradiation resistance,and oxidation resistance are reviewed in the aspect to the effect of interfaces.In addition,the relationships between these interfaces and material properties are discussed.Finally,future developments and potential new research directions for refractory alloys are proposed.展开更多
The Major ana zero mode(MZM), which manifests as an exotic neutral excitation in superconductors, is the building block of topological quantum computing. It has recently been found in the vortices of several iron-base...The Major ana zero mode(MZM), which manifests as an exotic neutral excitation in superconductors, is the building block of topological quantum computing. It has recently been found in the vortices of several iron-based superconductors as a zero-bias conductance peak in tunneling spectroscopy. In particular, a clean and robust MZM has been observed in the cores of free vortices in(Li_(0.84)Fe_(0.16))OHFeSe. Here using scanning tunneling spectroscopy, we demonstrate that Major ana-induced resonant Andreev reflection occurs between the STM tip and this zero-bias bound state,and consequently, the conductance at zero bias is quantized as 2e^2/h. Our results present a hallmark signature of the MZM in the vortex of an intrinsic topological superconductor, together with its intriguing behavior.展开更多
As one of the most important forming technologies for industrial bulk metallic glass (BMG) parts withcomplex shapes, high-pressure die casting (HPDC) can fill a die cavity with a glass-forming metallic liquidin millis...As one of the most important forming technologies for industrial bulk metallic glass (BMG) parts withcomplex shapes, high-pressure die casting (HPDC) can fill a die cavity with a glass-forming metallic liquidin milliseconds. However, to our knowledge, the correlation between flow and crystallization behavior inthe HPDC process has never been established. In this study, we report on the solidification behavior ofZr_(55)Cu_(30)Ni_(5)Al_(10) glass forming liquid under various flow rates. Surprisingly, the resulting alloys display adecreasing content of amorphous phase with increase of flow rate, i.e. increase of cooling rate, suggestingthat crystallization kinetics of glass-forming metallic liquids in the HPDC process is strongly dependenton the flow field. Analysis reveals that the accelerated crystallization behavior is mainly ascribed to therapid increase in viscosity with a decreasing temperature as well as to the huge shear effect in the glassforming liquid at the end stage of the filling process when the temperature is close to the glass-transitionpoint;this results in a transition from diffusion- to advection-dominated transport. The current investigation suggests that flow-related crystallization must be considered to assess the intrinsic glass-formingability of BMGs produced via HPDC. The obtained results will not only improve the understanding ofcrystallization dynamics but also promote the high-quality production and large-scale application of BMGparts.展开更多
The superτ-charm facility(STCF)is an electron–positron collider proposed by the Chinese particle physics community.It is designed to operate in a center-of-mass energy range from 2 to 7 GeV with a peak luminosity of...The superτ-charm facility(STCF)is an electron–positron collider proposed by the Chinese particle physics community.It is designed to operate in a center-of-mass energy range from 2 to 7 GeV with a peak luminosity of 0.5×10^(35) cm^(–2)·s^(–1) or higher.The STCF will produce a data sample about a factor of 100 larger than that of the presentτ-charm factory—the BEPCII,providing a unique platform for exploring the asymmetry of matter-antimatter(charge-parity violation),in-depth studies of the internal structure of hadrons and the nature of non-perturbative strong interactions,as well as searching for exotic hadrons and physics beyond the Standard Model.The STCF project in China is under development with an extensive R&D program.This document presents the physics opportunities at the STCF,describes conceptual designs of the STCF detector system,and discusses future plans for detector R&D and physics case studies.展开更多
Digital elevation model(DEM)matching techniques have been extended to DEM deformation detection by substituting a robust estimator for the least squares estimator,in which terrain changes are treated as gross errors.H...Digital elevation model(DEM)matching techniques have been extended to DEM deformation detection by substituting a robust estimator for the least squares estimator,in which terrain changes are treated as gross errors.However,all existing methods only emphasise their deformation detecting ability,and neglect another important aspect:only when the gross error can be detected and located,can this system be useful.This paper employs the gross error judgement matrix as a tool to make an in-depth analysis of this problem.The theoretical analyses and experimental results show that observations in the DEM matching algorithm in real applications have the ability to detect and locate gross errors.Therefore,treating the terrain changes as gross errors is theoretically feasible,allowing real DEM deformations to be detected by employing a surface matching technique.展开更多
For the development of high‐temperature superconducting(HTS)magnet systems of future fusion devices,a novel HTS round strand based on a stacking structure was designed and manufactured using second generation(2G)HTS ...For the development of high‐temperature superconducting(HTS)magnet systems of future fusion devices,a novel HTS round strand based on a stacking structure was designed and manufactured using second generation(2G)HTS tapes.Different mechanical loads during operation can result in irreversible degradation of the strand.The axial tension and fatigue loads need particular attention.Therefore,it is important to investigate the electromechanical behavior of the round strand under various axial tension and cyclic loads.In this paper,the axial tensile and fatigue tests were conducted at 77 K,self‐field.Taking 95%critical current(I_(c))retention as the criterion,the results of the tensile tests revealed that the average tensile stress and strain were as high as 344 MPa and 0.47%,respectively.Fatigue characteristics were also investigated as a function of axial tensile stress.No significant performance degradation was observed up to 100,000 loading cycles with stress amplitudes ranging from 20 MPa to 200 MPa.Ic degradation occurs after 16,000 loading cycles with 380 MPa as the maximum stress.Furthermore,the microscopic defects of the round strand samples due to fabrication imperfections and mechanical loading were investigated using metallographic microscope and scanning electron microscope.These results presented in this paper are useful for comprehending and improving the mechanical behaviors of the strand in high‐field and large‐scale fusion magnet systems.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant Nos.:51771184,11735015,51801203,51771181)the Natural Science Foundation of Anhui Province(Grant No.1808085QE132)+2 种基金the Open Project of State Key Laboratory of Environment friendly Energy Materials(18kfhg02)a fund from the Science and Technology on Surface Physics and Chemistry Laboratory(Grant No.JZX7Y201901SY00900103)the Innovation Center of Nuclear Materials for National Defense Industry。
文摘Refractory alloys such as tungsten and molybdenum based alloys with high strength,thermal/electrical conductivity,low coefficient of thermal expansion and excellent creep resistances are highly desirable for applications in nuclear facilities,critical components in aerospace and defense components.However,the serious embrittlement limits the engineering usability of some refractory alloys.A lot of research results indicate that the performances of refractory alloys are closely related to the physical/chemical status,such as the interface dimension,interface type,interface composition of their grain boundaries(GBs),phase boundaries(PBs)and other interface features.This paper reviewed the recent progress of simulations and experiments on interface design strategies that achieve high performance refractory alloys.These strategies include GB interface purifying/strengthening,PB interface strengthening and PB/GB synergistic strengthening.Great details are provided on the design/fabrication strategy such as GB interface controlling,PB interface controlling and synergistic control of multi-scaled interfaces.The corresponding performances such as the mechanical property,thermal conductivity,thermal load resistance,thermal stability,irradiation resistance,and oxidation resistance are reviewed in the aspect to the effect of interfaces.In addition,the relationships between these interfaces and material properties are discussed.Finally,future developments and potential new research directions for refractory alloys are proposed.
基金Supported by the National Natural Science Foundation of Chinathe National Key R&D Program of China under Grant Nos2016YFA0300200,2017YFA0303004 and 2017YFA0303003the Key Research of Frontier Sciences of CAS under Grant No QYZDY-SSW-SLH001
文摘The Major ana zero mode(MZM), which manifests as an exotic neutral excitation in superconductors, is the building block of topological quantum computing. It has recently been found in the vortices of several iron-based superconductors as a zero-bias conductance peak in tunneling spectroscopy. In particular, a clean and robust MZM has been observed in the cores of free vortices in(Li_(0.84)Fe_(0.16))OHFeSe. Here using scanning tunneling spectroscopy, we demonstrate that Major ana-induced resonant Andreev reflection occurs between the STM tip and this zero-bias bound state,and consequently, the conductance at zero bias is quantized as 2e^2/h. Our results present a hallmark signature of the MZM in the vortex of an intrinsic topological superconductor, together with its intriguing behavior.
基金L.H.Liu would like to thank the financial support from the National Natural Science Foundation of China(No.52001123)the China Postdoctoral Science Foundation(Nos.2019TQ0099 and 2019M662908)+5 种基金Guangdong Basic and the Applied Basic Research Foundation(No.2019A1515110215)the Foundation for Distinguished Young Talents in Higher Education of Guangdong(No.2019KQNCX003)the Fundamental Research Funds for the Central Universities(No.2020ZYGXZR030)the Open Fund of National Engineering Research Center of Near-net-shape Forming for Metallic Materials(No.2019003)C.Yang would like to thank the financial support from the Key Basic and Applied Research Program of Guangdong Province(No.2019B030302010)the National Natural Science Foundation of China(No.51971149).
文摘As one of the most important forming technologies for industrial bulk metallic glass (BMG) parts withcomplex shapes, high-pressure die casting (HPDC) can fill a die cavity with a glass-forming metallic liquidin milliseconds. However, to our knowledge, the correlation between flow and crystallization behavior inthe HPDC process has never been established. In this study, we report on the solidification behavior ofZr_(55)Cu_(30)Ni_(5)Al_(10) glass forming liquid under various flow rates. Surprisingly, the resulting alloys display adecreasing content of amorphous phase with increase of flow rate, i.e. increase of cooling rate, suggestingthat crystallization kinetics of glass-forming metallic liquids in the HPDC process is strongly dependenton the flow field. Analysis reveals that the accelerated crystallization behavior is mainly ascribed to therapid increase in viscosity with a decreasing temperature as well as to the huge shear effect in the glassforming liquid at the end stage of the filling process when the temperature is close to the glass-transitionpoint;this results in a transition from diffusion- to advection-dominated transport. The current investigation suggests that flow-related crystallization must be considered to assess the intrinsic glass-formingability of BMGs produced via HPDC. The obtained results will not only improve the understanding ofcrystallization dynamics but also promote the high-quality production and large-scale application of BMGparts.
基金supported by the National Key R&D Program of China under Contract No.2022YFA1602200the International Partnership Program of the Chineses Academy of Sciences under Grant No.211134KYSB20200057the STCF Key Technology Research and Development Project.
文摘The superτ-charm facility(STCF)is an electron–positron collider proposed by the Chinese particle physics community.It is designed to operate in a center-of-mass energy range from 2 to 7 GeV with a peak luminosity of 0.5×10^(35) cm^(–2)·s^(–1) or higher.The STCF will produce a data sample about a factor of 100 larger than that of the presentτ-charm factory—the BEPCII,providing a unique platform for exploring the asymmetry of matter-antimatter(charge-parity violation),in-depth studies of the internal structure of hadrons and the nature of non-perturbative strong interactions,as well as searching for exotic hadrons and physics beyond the Standard Model.The STCF project in China is under development with an extensive R&D program.This document presents the physics opportunities at the STCF,describes conceptual designs of the STCF detector system,and discusses future plans for detector R&D and physics case studies.
基金This research is supported by the National High Technology Plan(863)of the People’s Republic of China,Project No.2009AA12Z207.
文摘Digital elevation model(DEM)matching techniques have been extended to DEM deformation detection by substituting a robust estimator for the least squares estimator,in which terrain changes are treated as gross errors.However,all existing methods only emphasise their deformation detecting ability,and neglect another important aspect:only when the gross error can be detected and located,can this system be useful.This paper employs the gross error judgement matrix as a tool to make an in-depth analysis of this problem.The theoretical analyses and experimental results show that observations in the DEM matching algorithm in real applications have the ability to detect and locate gross errors.Therefore,treating the terrain changes as gross errors is theoretically feasible,allowing real DEM deformations to be detected by employing a surface matching technique.
基金supported by the Southwestern Institute of Physics(SWIP)under project number 202101XWCXRZ001 and 2021XWCXRZ002.
文摘For the development of high‐temperature superconducting(HTS)magnet systems of future fusion devices,a novel HTS round strand based on a stacking structure was designed and manufactured using second generation(2G)HTS tapes.Different mechanical loads during operation can result in irreversible degradation of the strand.The axial tension and fatigue loads need particular attention.Therefore,it is important to investigate the electromechanical behavior of the round strand under various axial tension and cyclic loads.In this paper,the axial tensile and fatigue tests were conducted at 77 K,self‐field.Taking 95%critical current(I_(c))retention as the criterion,the results of the tensile tests revealed that the average tensile stress and strain were as high as 344 MPa and 0.47%,respectively.Fatigue characteristics were also investigated as a function of axial tensile stress.No significant performance degradation was observed up to 100,000 loading cycles with stress amplitudes ranging from 20 MPa to 200 MPa.Ic degradation occurs after 16,000 loading cycles with 380 MPa as the maximum stress.Furthermore,the microscopic defects of the round strand samples due to fabrication imperfections and mechanical loading were investigated using metallographic microscope and scanning electron microscope.These results presented in this paper are useful for comprehending and improving the mechanical behaviors of the strand in high‐field and large‐scale fusion magnet systems.
