Influence of two-stage annealing treatment on critical current of bronze-processed multifilamentary Nb3Sn superconducting materials

Ochiai, Shojiro; Osamura, Kōzō; Ryoji, Makoto

doi:10.1016/0001-6160(87)90089-7

Cited by 19 publications

(6 citation statements)

References 23 publications

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“…This kind of investigation may suggest how to decrease the double composition gradient observed here. Decreasing both gradients, while limiting A15 grain growth might be enabled by two-step heat treatments similar to those now being performed on PIT wires [47] and commonly used in bronze route wire [48,49]. Understanding the compromises in all present state-of-the-art Nb 3 Sn wires is clearly not a qualitative issue but a highly detailed quantitative issue, where choices have to be made between optimizing the intrinsic properties such as T c and H c2 at the expense of extrinsic properties such as GB density and diffusion barrier integrity.…”

Section: Comparison To Other Conductor Designs and Some Broader Impli...mentioning

confidence: 99%

Examination of the trade-off between intrinsic and extrinsic properties in the optimization of a modern internal tin Nb₃Sn conductor

Tarantini

Lee

Craig

et al. 2014

Supercond. Sci. Technol.

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In modern Nb 3 Sn wires there is a fundamental compromise to be made between optimizing the intrinsic properties associated with the superfluid density in the A15 phase (e.g. T c , H c , H c2 , all of which are composition dependent), maximizing the quantity of A15 that can be formed from a given mixture of Nb, Sn and Cu, minimizing the A15 composition gradients within each sub-element, while at the same time generating a high vortex pinning critical current density, J c , by maximizing the grain boundary density with the additional constraint of maintaining the RRR of the Cu stabilizer above 100. Here we study these factors in a Ta-alloyed Restacked-Rod-Process (RRP ® ) wire with ~70 m diameter sub-elements. Consistent with many earlier studies, maximum non-Cu J c (12 T, 4.2 K) requires preventing A15 grain growth, rather than by optimizing the superfluid density. In wires optimized for 12 T, 4.2 K performance, about 60% of the non-Cu cross-section is A15, 35% residual Cu and Sn core, and only 5% a residual Nb-7.5wt.%Ta diffusion barrier. The specific heat and chemical analyses show that in this 60% A15 fraction there is a wide range of T c and chemical composition that does diminish for higher heat treatment temperatures, which, however, are impractical because of the strong RRR degradation that occurs when only about 2% of the A15 reaction front breaches the diffusion barrier. As this kind of Nb 3 Sn conductor design is being developed for sub-elements about half the present size, it is clear that better barriers are essential to allowing higher temperature reactions with better intrinsic A15 properties. We present here multiple and detailed intrinsic and extrinsic evaluations because we believe that only such broad and quantitative descriptions are capable of accurately tracking the limitations of individual conductor designs where optimization will always be a compromise between inherently conflicting goals. | P a g eRestack-Process (RRP ® ) design can easily provide non-Cu J c (12 T, 4.2 K) > 3000 A/mm 2 but struggle to produce long-piece length conductors with d eff < 35-40 m [4], while PIT conductors struggle to produce non-Cu J c (12 T, 4.2 K) exceeding 2500 A/mm 2 , although they do offer a slightly smaller sub-element size [5]. The present paper seeks to understand the way that a balance of intrinsic (T c , H c2 , Sn content, …) and extrinsic (partition of real estate between Sn, Cu, Nb(Ta) and diffusion barrier, A15 grain boundary density, J c , …) factors controls the properties of a modern high performance RRP ® conductor designed for demanding accelerator use, while a subsequent paper will explore some aspects of the same issue for recent PIT conductors.The further development of high performance Nb 3 Sn should be enabled by a more detailed understanding of the A15 composition, grain morphology, wire structure and strain that until now has been evaluated in a mostly ad hoc, empirical way. In fact the optimization of modern Nb 3 Sn conductors in terms of their Cu:Nb:Sn ratio, effectiveness of dopi...

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Section: Comparison To Other Conductor Designs and Some Broader Impli...mentioning

confidence: 99%

Examination of the trade-off between intrinsic and extrinsic properties in the optimization of a modern internal tin Nb₃Sn conductor

Tarantini

Lee

Craig

et al. 2014

Supercond. Sci. Technol.

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“…Commercial fabrication of the Nb 3 Sn superconducting composites of long lengths is presently performed by three approaches: the bronze route [19][20][21], the internal-tin route [22][23][24][25][26][27] and the powder in tube (PIT) approach [28][29][30].…”

Section: Brief Comparison Of Modern Manufacturing Routes For the Nb 3...mentioning

confidence: 99%

Morphology and Structure of Diffusion Layers in Nb<sub>3</sub>Sn-Based Superconductors of Different Geometry

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Deryagina

2015

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The evolution of structure and morphology of superconducting Nb3Sn layers forming under various regimes of the diffusion annealing in multifilamentary Nb/Cu–Sn superconductors of different design is briefly reviewed based on the authors’ (with their coauthors) original studies and the available publications. Different modes of the solid-state diffusion formation of the superconducting phase are compared. Possible mechanisms of the Nb3Sn nucleation upon the diffusion reaction of the Nb filaments and bronze matrixes are discussed. The effects of different doping elements, especially Ti, on the formation of the superconducting phase, its structure and morphology, and, consequently, on the current-carrying capacities of multifilamentary Nb3Sn-based wires are considered. Special attention is paid to the effect of the mode of Ti doping, the content of this alloying element and the regimes of the diffusion annealing on the structure, morphology and resulting performance of the bronze-processed wires with coupled Nb filaments worked out at Bochvar Institute of Inorganic Materials for the creation of International Thermonuclear Experimental Reactor.

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“…At the lower end of this range the compound growth rate is very slow leading to unacceptably long reaction times [8], in addition the compound is disordered and has a high level of point defects exhibiting a degraded value of T c and B c2 [9]. Above 750…”

Section: Improvement Of Nb 3 Sn Pinningmentioning

confidence: 99%

Pinning Improvement of A15 Applied Superconducting Materials

Glowacki

2016

Acta Phys. Pol. A

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Electron-phonon coupling is one of the most common interaction in superconducting materials ranging from Nb3Sn, MgB2, iron-based superconductors and high temperature cuprates such as YBa2Cu3O 7−δ and HgBa2Ca2Cu3O 8+δ . However an importance of the electron-phonon coupling constant, λep, should not be underestimated for characterisation of the electronic properties of superconducting materials, but it is important that the enhanced flux pinning mechanism can be hold responsible for the applicability of the A15 superconducting materials in emerging hydrogen cryomagnetic technology where temperature of the liquid H2 can be as low as 14 K.

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Influence of two-stage annealing treatment on critical current of bronze-processed multifilamentary Nb3Sn superconducting materials

Cited by 19 publications

References 23 publications

Examination of the trade-off between intrinsic and extrinsic properties in the optimization of a modern internal tin Nb₃Sn conductor

Examination of the trade-off between intrinsic and extrinsic properties in the optimization of a modern internal tin Nb₃Sn conductor

Morphology and Structure of Diffusion Layers in Nb<sub>3</sub>Sn-Based Superconductors of Different Geometry

Pinning Improvement of A15 Applied Superconducting Materials

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Influence of two-stage annealing treatment on critical current of bronze-processed multifilamentary Nb3Sn superconducting materials

Cited by 19 publications

References 23 publications

Examination of the trade-off between intrinsic and extrinsic properties in the optimization of a modern internal tin Nb3Sn conductor

Examination of the trade-off between intrinsic and extrinsic properties in the optimization of a modern internal tin Nb3Sn conductor

Morphology and Structure of Diffusion Layers in Nb<sub>3</sub>Sn-Based Superconductors of Different Geometry

Pinning Improvement of A15 Applied Superconducting Materials

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Examination of the trade-off between intrinsic and extrinsic properties in the optimization of a modern internal tin Nb₃Sn conductor

Examination of the trade-off between intrinsic and extrinsic properties in the optimization of a modern internal tin Nb₃Sn conductor