Large critical current density improvement in Bi-2212 wires through the groove-rolling process

Malagoli, Andrea; Bernini, C.; Braccini, V.; Romano, G.; Putti, M.; Chaud, X.; Debray, F.

doi:10.1088/0953-2048/26/4/045004

Cited by 18 publications

(17 citation statements)

References 23 publications

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“…All the described approaches, though reaching extremely appealing J C values, might not be as simple and straightforward over long lengths and coils. Aiming at developing a cheap and easily industrially scalable technique, we studied a different approach to densify the wire at an earlier stage using a different deformation technique in making Bi-2212 conductors [11]. We explored the groove-rolling process, whose peculiar characteristic compared to drawing is the difference in deformation forces exerted on the metallic sheath: during the groove rolling, the component of the force transversal with respect to the wire axis is higher resulting in a larger powders compaction capability.…”

Section: Introductionmentioning

confidence: 99%

Groove-rolling as an alternative process to fabricate Bi-2212 wires for practical applications

Malagoli¹,

Braccini²,

Vignolo³

et al. 2014

Supercond. Sci. Technol.

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Bi 2 Sr 2 CaCu 2 O 8+x (Bi-2212) superconducting long-length wires are mainly limited in obtaining high critical currents densities (J C ) by the internal gas pressure generated during the heat treatment, which expands the wire diameter and dedensifies the superconducting filaments. Several ways have been developed to increase the density of the superconducting filaments and therefore decreasing the bubble density: much higher critical currents have been reached always acting on the final as-drawn wires. We here try to pursue the same goal of having a denser wire by acting on the deformation technique, through a partial use of the groove-rolling at different wire processing stages. Such technique has a larger powders compaction power, is straightforwardly adaptable to long length samples, and allows the fabrication of samples with round, square or rectangular shape depending on the application requirements. In this paper we demonstrate the capability of this technique to increase the density in Bi-2212 wires which leads to a three-fold increase in Jc with respect to drawn wires, making this approach very promising for fabricating Bi-2212 wires for high magnetic field magnets, i.e. above 25 T.

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Section: Introductionmentioning

confidence: 99%

Groove-rolling as an alternative process to fabricate Bi-2212 wires for practical applications

Malagoli¹,

Braccini²,

Vignolo³

et al. 2014

Supercond. Sci. Technol.

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“…In our previous publications [7,8], we demonstrated the ability of groove-rolling to increase the density in Bi-2212 wires, leading to a threefold increase in Jc with respect to drawn wires in square and rectangular wires with various architectures. Jc up to 2000 A/mm 2 were measured in open ends wires, but the remarkable result was the reduction of only 28% between open-and closed-ends wires which is much lower than the 70% reduction observed in the commercial OST wires, clear indication of a higher density reached through groove-rolling [8].…”

Section: Introductionmentioning

confidence: 85%

“…In Figure 3 we report the longitudinal cross sections of the square wire at the end of the deformation process and after the full heat treatment, in both cases compared with the longitudinal cross section of a round wire prepared only through drawing, with a diameter of 0.8 mm and the same internal architecture [7]. Filaments size is about the same for the two wires.…”

Section: Figure2 Jc (Left Axis) and Je (Right Axis) For The A) Rectamentioning

confidence: 99%

New concept for the development of Bi-2212 wires for high-field applications

Leveratto

Braccini

Contarino

et al. 2016

Supercond. Sci. Technol.

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The first step towards high critical currents in Bi-2212 wires was the comprehension that the supercurrent is blocked over long lengths by filament-diameter bubbles grown during the melt stage, which cause expansion of the wire diameter and dedensification of the superconducting filaments.Whereas the previous successful approach to reduce the problem of voids related to bubbles was based on the application of a high overpressure during the heat treatment, we fabricated Bi-2212 wires by applying a new concept of suitably alternating groove-rolling and drawing techniques with the aim of densifying the phase already during the working procedure prior to the heat treatment.We here for the first time were able to reach in wires reacted with closed ends -i.e. with gas trapped in the wire as it happens in long-length wires -the very same values of critical current shown in short wires reacted with open ends. This is the irrefutable evidence that, only by acting on the deformation technique, we were able to raise the critical current by properly densifying the superconducting powder inside the filaments already before the melt stage. Whole-conductor current densities in our long length simulation wires already reach 400 A/mm 2 at 4.2 K and 5 T, which can be still easily increased through architecture optimization. The actual breakthrough is that the densification is optimized without further complex treatments through a technique which can be straightforwardly applied to long-lengths wires.

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“…21 , 22 The critical current density ( J c ) is a major bottleneck for superconducting materials in wire applications, by placing a limit on the current that could pass through them. 23 The developments of Bi-based superconducting wires with high J c property have been continued for practical use such as training-quench-free coils. 24 − 26 The most important strategy for enhancing J c in superconducting wires is to grow strong pinning centers.…”

Section: Introductionmentioning

confidence: 99%

Crystal Growth and High-Pressure Effects of Bi-Based Superconducting Whiskers

Matsumoto¹,

Yamamoto

Takano

et al. 2021

ACS Omega

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Three growth methods were tested for producing high-transition temperature superconducting Bi 2 Sr 2 Ca n –1 Cu n O 2 n +4+δ whiskers, employing different ways to focus a compressive stress and size effect of the precursors. First, thermographic imaging was used to investigate thermal stress from temperature distribution in the precursors during growth annealing. To enhance thermal stress in the precursors, a thermal cycling method and a Ag-paste coating method were proposed and found to significantly accelerate the whisker growth. The use of pulverized precursors also promoted whisker growth, possibly due to contribution from the vapor–liquid–solid growth mechanism. The obtained whiskers revealed the typical composition, diffraction patterns, and superconducting properties of the Bi-2212 phase. The proposed methods were able to stably produce longer whiskers compared to the conventional method. Using the obtained whiskers, electrical transport measurements under high pressure were successfully performed up to around 50 GPa.

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Large critical current density improvement in Bi-2212 wires through the groove-rolling process

Cited by 18 publications

References 23 publications

Groove-rolling as an alternative process to fabricate Bi-2212 wires for practical applications

Groove-rolling as an alternative process to fabricate Bi-2212 wires for practical applications

New concept for the development of Bi-2212 wires for high-field applications

Crystal Growth and High-Pressure Effects of Bi-Based Superconducting Whiskers

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