The element diffusion process of Nb_3Sn superconductors by bronze route was studied using X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. The critical current of superconductors was...The element diffusion process of Nb_3Sn superconductors by bronze route was studied using X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. The critical current of superconductors was measured by four-point method. The results show that a diffusion layer has formed around the boundaries between the filaments and bronze matrix after 15 h heat treatment. The diffusion layer thickness keeps stable after heat treatment duration of 50~75 h. The stable and solid Nb 3 Sn layer is obtained in the sample after 100 h heat treatment. Excessive heat treatment would induce superconductivity degeneration because of superconductor grain coarsening. The characteristics of the element diffusion process were discussed. The diffusion of tin atom is the governing factor in diffusion. In this study, Nb_3_Sn superconductors with good superconducting property were fabricated successfully at 670 °C after 100h heat treatment.展开更多
The diffusion process of Sn in the transformation of Nb_6Sn_5 to Nb_3Sn has been studied.The experimental results show that the growth of Nb_3Sn laver is controlled by two processes,i.e. the short range diffusion of S...The diffusion process of Sn in the transformation of Nb_6Sn_5 to Nb_3Sn has been studied.The experimental results show that the growth of Nb_3Sn laver is controlled by two processes,i.e. the short range diffusion of Sn which is responsihle for the inner layer with large grains,and the long,range diffusion of Sn which results in the outer layer with fine grains.It was found thai grain size depends on the reaction temperature.A model of Nb_3Sn growth based on the above processes was established and its solution was found to be in good agreement with ex- perimental results.展开更多
High-field superconducting magnets are poised to revolutionize technologies,including particle accelerators,magnetic resonance imaging(MRI)machines,and fusion reactors.They stand at the frontier of superconductor inno...High-field superconducting magnets are poised to revolutionize technologies,including particle accelerators,magnetic resonance imaging(MRI)machines,and fusion reactors.They stand at the frontier of superconductor innovation.Nb_(3)Sn wires,which operate at cold temperatures,along with rare-earth barium copper oxide(REBCO)coated conductors that include rare earth elements like Y,Gd,and Dy,are gaining preference.Their high electrical efficiency in strong magnetic fields makes them particularly attractive for such advanced applications.展开更多
Boundary conditions constructed by two typical geometrical configurations related to the manufacturing methods of bronze process and tin-rich Nb tube method have been considered in a diffusion model in which the diffu...Boundary conditions constructed by two typical geometrical configurations related to the manufacturing methods of bronze process and tin-rich Nb tube method have been considered in a diffusion model in which the diffusion of Sn in CuSn matrix plays a major role is as- sumed.The dependence of thickness of Nb_3Sn layer on reaction time has been derived.It is shown that the growth rate of Nb_3Sn relates to the configuration of the superconductor,the geometrical parameters of Nb filaments and CuSn matrix.The theory is qualitatively con- sistent with the experimental results.展开更多
At present,Nb_(3) Sn superconductors are becoming more popular in high magnetic fields.The growth law of Nb_(3) Sn phase in a planar CuSn/Nb diffusion couple has been studied,whereas the formation mechanism of Nb_(3) ...At present,Nb_(3) Sn superconductors are becoming more popular in high magnetic fields.The growth law of Nb_(3) Sn phase in a planar CuSn/Nb diffusion couple has been studied,whereas the formation mechanism of Nb_(3) Sn phase in a cylindrical CuSn/Nb diffusion couple is still controversial.The purpose of this work is to investigate the growth exponent of Nb_(3) Sn phase at the initial stage of annealing by use of scanning electron microscopy(SEM)through which the thickness of Nb_(3) Sn layer can be obtained.In this study,bronze-processed Nb_(3) Sn multifilamentary wires with different annealing time were investigated.The Nb_(3) Sn phase was formed during isothermal annealing at 670 ℃ by solid-state diffusion,which was accomplished by the movement of Sn atoms from the CuSn/Nb_(3) Sn interface to Nb_(3) Sn/Nb interface.However,the formation mechanism of Nb_(3) Sn phase at the initial stage of annealing is still not well understood.Microstructural evolution of Nb_(3) Sn phase during isothermal annealing was studied by SEM.The mean thickness of the Nb_(3) Sn layer(Δ(xNn3 Sn)) is expressed as a power function of the annealing time(t) by the equation A_(x^(2)Nb_(3) Sn)=k(t/t0)^(n),where t0 is the unit time,k is the reaction rate constant and n is the growth exponent.The growth exponent has the average value of 0.82,which means that the formation of the Nb_(3) Sn phase is both governed by the interface reaction and the grain boundary diffusion.展开更多
基金supported by the National Natural Science Foundation of China(No.50925726)
文摘The element diffusion process of Nb_3Sn superconductors by bronze route was studied using X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. The critical current of superconductors was measured by four-point method. The results show that a diffusion layer has formed around the boundaries between the filaments and bronze matrix after 15 h heat treatment. The diffusion layer thickness keeps stable after heat treatment duration of 50~75 h. The stable and solid Nb 3 Sn layer is obtained in the sample after 100 h heat treatment. Excessive heat treatment would induce superconductivity degeneration because of superconductor grain coarsening. The characteristics of the element diffusion process were discussed. The diffusion of tin atom is the governing factor in diffusion. In this study, Nb_3_Sn superconductors with good superconducting property were fabricated successfully at 670 °C after 100h heat treatment.
文摘The diffusion process of Sn in the transformation of Nb_6Sn_5 to Nb_3Sn has been studied.The experimental results show that the growth of Nb_3Sn laver is controlled by two processes,i.e. the short range diffusion of Sn which is responsihle for the inner layer with large grains,and the long,range diffusion of Sn which results in the outer layer with fine grains.It was found thai grain size depends on the reaction temperature.A model of Nb_3Sn growth based on the above processes was established and its solution was found to be in good agreement with ex- perimental results.
文摘High-field superconducting magnets are poised to revolutionize technologies,including particle accelerators,magnetic resonance imaging(MRI)machines,and fusion reactors.They stand at the frontier of superconductor innovation.Nb_(3)Sn wires,which operate at cold temperatures,along with rare-earth barium copper oxide(REBCO)coated conductors that include rare earth elements like Y,Gd,and Dy,are gaining preference.Their high electrical efficiency in strong magnetic fields makes them particularly attractive for such advanced applications.
基金the National Natural Science Foundation of China(Grant Nos.11602185,11972271,and 12322208)the Young Elite Scientists Sponsorship Program by CAST(Grant No.2020QNRC001)the Fundamental Research Funds for the Central Universities.
文摘Boundary conditions constructed by two typical geometrical configurations related to the manufacturing methods of bronze process and tin-rich Nb tube method have been considered in a diffusion model in which the diffusion of Sn in CuSn matrix plays a major role is as- sumed.The dependence of thickness of Nb_3Sn layer on reaction time has been derived.It is shown that the growth rate of Nb_3Sn relates to the configuration of the superconductor,the geometrical parameters of Nb filaments and CuSn matrix.The theory is qualitatively con- sistent with the experimental results.
基金financially supported by the Nuclear Material Technology Innovation Center for National Defense Technology and Industry(No.ICNM-2019-YZ-03)。
文摘At present,Nb_(3) Sn superconductors are becoming more popular in high magnetic fields.The growth law of Nb_(3) Sn phase in a planar CuSn/Nb diffusion couple has been studied,whereas the formation mechanism of Nb_(3) Sn phase in a cylindrical CuSn/Nb diffusion couple is still controversial.The purpose of this work is to investigate the growth exponent of Nb_(3) Sn phase at the initial stage of annealing by use of scanning electron microscopy(SEM)through which the thickness of Nb_(3) Sn layer can be obtained.In this study,bronze-processed Nb_(3) Sn multifilamentary wires with different annealing time were investigated.The Nb_(3) Sn phase was formed during isothermal annealing at 670 ℃ by solid-state diffusion,which was accomplished by the movement of Sn atoms from the CuSn/Nb_(3) Sn interface to Nb_(3) Sn/Nb interface.However,the formation mechanism of Nb_(3) Sn phase at the initial stage of annealing is still not well understood.Microstructural evolution of Nb_(3) Sn phase during isothermal annealing was studied by SEM.The mean thickness of the Nb_(3) Sn layer(Δ(xNn3 Sn)) is expressed as a power function of the annealing time(t) by the equation A_(x^(2)Nb_(3) Sn)=k(t/t0)^(n),where t0 is the unit time,k is the reaction rate constant and n is the growth exponent.The growth exponent has the average value of 0.82,which means that the formation of the Nb_(3) Sn phase is both governed by the interface reaction and the grain boundary diffusion.
