Results on mono element internal tin Nb/sub 3/Sn conductors (MEIT) with Nb7.5Ta and Nb(1Zr+O/sub x/) filaments

Zeitlin, B. A.; Gregory, E.; Marte, J.; Benz, M. G.; Pyon, T.; Scanlan, R.M.; Dietderich, D.R.

doi:10.1109/tasc.2005.848917

Cited by 16 publications

(19 citation statements)

References 3 publications

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“…In a Nb3Sn wire, due to the presence of the outside Cu sheath, oxygen cannot be delivered to the Nb-Zr alloy externally (e.g., by anodization or by annealing in an oxygen atmosphere). Benz ([97]) and Zeitlin [98] tried to pre-dissolve oxygen in Nb-1%Zr alloy and to use this oxygen-containing Nb-1%Zr for wire fabrication. However, the oxygen-containing Nb-1%Zr alloy was hard to draw, because the pre-dissolved oxygen markedly increased its strength and decreased its ductility.…”

Section: Prospects To Improve Pinning Capacitymentioning

confidence: 99%

A review and prospects for Nb₃Sn superconductor development

2017

Supercond. Sci. Technol.

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Nb3Sn superconductors have significant applications in constructing high-field (> 10 T) magnets. This article briefly reviews development of Nb3Sn superconductor and proposes prospects for further improvement. It is shown that significant improvement of critical current density (Jc) is needed for future accelerator magnets. After a brief review of the development of Nb3Sn superconductors, the factors controlling Jc are summarized and correlated with their microstructure and chemistry. The non-matrix Jc of Nb3Sn conductors is mainly determined by three factors: the fraction of current-carrying Nb3Sn phase in the non-matrix area, the upper critical field Bc2, and the flux-line pinning capacity. Then prospects to improve the three factors are discussed respectively. An analytic model was developed to show how the ratios of precursors determine the phase fractions after heat treatment, based on which it is predicted that the limit of current-carrying Nb3Sn fraction in subelements is ~65%. Then, since Bc2 is largely determined by the Nb3Sn stoichiometry, a thermodynamic/kinetic theory was presented to show what essentially determines the Sn content of Nb3Sn conductors. This theory explains the influences of Sn sources and Ti addition on stoichiometry and growth rate of Nb3Sn layers. Next, to improve flux pinning, previous efforts in this community to introduce additional pinning centers (APC) to Nb3Sn wires are reviewed, and an internal oxidation technique is described.Finally, prospects for further improvement of non-matrix Jc of Nb3Sn conductors are discussed, 2 and it is seen that the only opportunity for further significantly improving Jc lies in improving the flux pinning.

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Section: Prospects To Improve Pinning Capacitymentioning

confidence: 99%

A review and prospects for Nb₃Sn superconductor development

2017

Supercond. Sci. Technol.

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“…To apply this method to a Nb 3 Sn strand, commercially available Nb–1wt% Zr alloy (in place of the usual Nb or Nb–Ta alloy) can be used because Zr, according to the Ellingham diagram, has much stronger affinity to oxygen than Nb does, making internal oxidation of the alloy possible . Oxygen supply, on the other hand, needs special attention.…”

mentioning

confidence: 99%

“…Oxygen cannot be delivered to a Nb 3 Sn strand externally, because the outer Cu sheath will block oxygen transport to the Nb–Zr alloy (this is clear from a kinetics calculation, and is verified by our experiments). Pre‐dissolving oxygen in the Nb–1Zr alloy is not feasible either, because the precursor Nb–Sn composite is processed down from a large billet to a small diameter (typically tens of micrometer) filament, and the relatively high hardness of oxygen‐containing Nb–Zr makes processing difficult . In this work, oxide powder is added into the composite to supply oxygen within the strand .…”

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Internally Oxidized Nb₃Sn Strands with Fine Grain Size and High Critical Current Density

Sumption

Peng

2015

Advanced Materials

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Nb 3 Sn superconducting strands are the most practical conductors to generate high magnetic fields (12-16 T), and thus have significant applications in nuclear magnetic resonance (NMR), and great potential for fusion reactors and particle accelerator magnets. High critical current density (J c ) is a key parameter for such applications. Significant efforts towards optimization of various factors led to an 80% improvement in J c from the early 1990s to 2003, when the 4.2 K, 12 T non-matrix J c reached 3000 A/mm 2 (corresponding to 5000 A/mm 2 in Nb 3 Sn layer J c ). [1,2] However, further efforts over the past decade have failed to bring about further increase beyond this level, [3,4] leading some researchers to conclude that the J c of conventional Nb 3 Sn strands had reached its maximum. Here, however, by applying an internal oxidation method, we reduce the grain size by a factor of three and nearly double the 12 T J c . In this method, a Nb 3 Sn strand is fabricated with Nb-Zr alloy as starting material; with oxygen supplied properly via an oxide powder, the Zr atoms in the Nb-Zr alloy are internally oxidized, forming fine intra-granular and inter-granular ZrO 2 particles in Nb 3 Sn layer, which effectively refine Nb 3 Sn grain size. At a reaction temperature of 625 °C, grain size down to 20-50 nm (36 nm on average) has been achieved. For this sample the 4.2 K, 12 T Nb 3 Sn layer J c reached 9600 A/mm 2 .

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“…In the recent years, most doping experiments have been performed on bronze-processed strands [15], but internal-Sn strands also contain Ti [16] or Ta [17] additives. More recently, Zr addition to Nb 3 Sn strands was also proposed [18].…”

Section: Introductionmentioning

confidence: 99%

Characterizations of A15 Phase Composition and $T_{c}$ for Internal-Sn $\hbox{Nb}_{3}\hbox{Sn}$ Strands

Zhang

Sulpice²,

Zhou³

et al. 2010

IEEE Trans. Appl. Supercond.

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Four sets of monoelementary (ME) and two kinds of multifilamentary (MF) internal-Sn Nb 3 Sn superconducting strands were designed and fabricated, in which various component ratios, different composite configurations, and some third-element additions were arranged. All strands were submitted to a first heat treatment (HT) of 210 • C/50 h + 340 • C/25 h for Cu-Sn mixing, followed by the A15 phase formation HT. The four ME strands were reacted at 675 • C, 700 • C, and 725 • C for 100 and 200 h, respectively, and the two MF strands at 650 • C, 675 • C, 700 • C, and 725 • C for 128 and 200 h, respectively. The analysis of the reacted strands comprised the A15 phase composition distribution by means of X-ray energy-dispersive spectroscopy and the critical temperature T c by means of superconducting quantum interference device magnetization measurements. The obtained results indicate that, for sufficiently reacted internal-Sn Nb 3 Sn strands, the final A15 phase composition and T c are determined by the diffusion and solid reaction mechanism of the A15 phase formation. In particular, the onset T c values and the average Sn content in a grain do not depend on the reaction temperature, the local compositions in the strand, the composite configuration arrangement, and the third-element addition.Index Terms-A15 phase composition, composite component and configuration, internal-Sn Nb 3 Sn strands, phase formation heat treatment (HT), third-element addition.

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Results on mono element internal tin Nb/sub 3/Sn conductors (MEIT) with Nb7.5Ta and Nb(1Zr+O/sub x/) filaments

Cited by 16 publications

References 3 publications

A review and prospects for Nb₃Sn superconductor development

A review and prospects for Nb₃Sn superconductor development

Internally Oxidized Nb₃Sn Strands with Fine Grain Size and High Critical Current Density

Characterizations of A15 Phase Composition and $T_{c}$ for Internal-Sn $\hbox{Nb}_{3}\hbox{Sn}$ Strands

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Results on mono element internal tin Nb/sub 3/Sn conductors (MEIT) with Nb7.5Ta and Nb(1Zr+O/sub x/) filaments

Cited by 16 publications

References 3 publications

A review and prospects for Nb3Sn superconductor development

A review and prospects for Nb3Sn superconductor development

Internally Oxidized Nb3Sn Strands with Fine Grain Size and High Critical Current Density

Characterizations of A15 Phase Composition and $T_{c}$ for Internal-Sn $\hbox{Nb}_{3}\hbox{Sn}$ Strands

Contact Info

Product

Resources

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A review and prospects for Nb₃Sn superconductor development

A review and prospects for Nb₃Sn superconductor development

Internally Oxidized Nb₃Sn Strands with Fine Grain Size and High Critical Current Density