Void and phase evolution during the processing of Bi-2212 superconducting wires monitored by combined fast synchrotron micro-tomography and x-ray diffraction

Scheuerlein, C.; Michiel, Marco Di; Scheel, Mario; Jiang, J.; Kametani, F.; Malagoli, Andrea; Hellstrom, E. E.; Larbalestier, D. C.

doi:10.1088/0953-2048/24/11/115004

Cited by 45 publications

(47 citation statements)

References 22 publications

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“…Previously we have reported on the formation of porosity and the phase changes occurring in a Bi-2212 wire during processing in pO2=0.21 bar [6]. In this article we report for the first time the direct observation of the phase changes during heat cycles at pO2≥1 bar.…”

Section: Introductionmentioning

confidence: 59%

“…During the in situ HTs one pattern was acquired every 5 minutes. More details about the diffraction experiment can be found in [5] and [6].…”

Section: B X-ray Diffractionmentioning

confidence: 99%

“…The HTs in ambient air have been performed under a continuous gas flow at ambient pressure in the ID15 tomography furnace, as described in [6].…”

Section: Temperature and Oxygen Partial Pressure Controlmentioning

confidence: 99%

See 2 more Smart Citations

Influence of the Oxygen Partial Pressure on the Phase Evolution During Bi-2212 Wire Melt Processing

Scheuerlein¹,

Andrieux²,

Rikel³

et al. 2016

IEEE Trans. Appl. Supercond.

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Abstract-We have studied the influence of the oxygen partial pressure pO2 up to 5.5 bar on the phase changes that occur during melt processing of a state-of-the-art Bi-2212 multifilamentary wire. Phase changes have been monitored in situ by high energy synchrotron X-ray diffraction (XRD). We found that the stability of Bi-2212 phase is reduced with increasing pO2. For pO2>1 bar a significant amount of Bi-2212 phase decomposes upon heating in the range 400 to 650 °C. The extent of decomposition strongly increases with increasing pO2, and at pO2=5.5 bar Bi-2212 decomposes completely in the solid state. Textured Bi-2212 can be formed during solidification when pO2 is reduced to 0.45 bar when the precursor is molten. Since the formation of current limiting second phases is very sensitive to pO2 when it exceeds 1 bar, we recommend to reduce the oxygen partial pressure below the commonly used pO2=1 bar, in order to increase the pO2 margins and to make the overpressure process more robust.  Index Terms-Bi-2212, melt processing, XRD.

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Section: Introductionmentioning

confidence: 59%

“…During the in situ HTs one pattern was acquired every 5 minutes. More details about the diffraction experiment can be found in [5] and [6].…”

Section: B X-ray Diffractionmentioning

confidence: 99%

See 1 more Smart Citation

Influence of the Oxygen Partial Pressure on the Phase Evolution During Bi-2212 Wire Melt Processing

Scheuerlein¹,

Andrieux²,

Rikel³

et al. 2016

IEEE Trans. Appl. Supercond.

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“…Previous studies by Shen et al [8], Kametani et al [10] and Scheuerlein et al [11] showed clearly that the gas in the wire agglomerates into filament size bubbles when Bi-2212 melts. When Bi-2212 reforms on cooling, the bubbles can be partially filled by new plate-like Bi-2212 grains, but the original bubble structure remains, even in fully-processed wires, leaving unsupported bridges of Bi-2212 shown earlier by Kametani et al [10].…”

Section: Discussionmentioning

confidence: 93%

“…It is well known that long lengths have several times lower J c than short samples and this has meant that so far no Bi-2212 user magnets have been made. The earlier studies of Shen et al [8], Malagoli et al [9], Kametani et al [10], and Scheuerlein et al [11] provide firm evidence that the large gas bubbles formed during the excursion into the melt state provide the major present current-limiting mechanism in round-wire Bi-2212 conductors. A recent study by Malagoli et al [12] on the length-dependent expansion of a Bi-2212 wire after full heat treatment showed that gas pressure provokes a wire diameter expansion which increases with distance from the ends, longer samples (up to 2.4 m) often showing evident damage and leaks caused by the internal pressure.…”

mentioning

confidence: 92%

Reduction of Gas Bubbles and Improved Critical Current Density in Bi-2212 Round Wire by Swaging

Jiang

Miao²,

Huang³

et al. 2013

IEEE Trans. Appl. Supercond.

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Bi-2212 round wire is made by the powder-in-tube technique. An unavoidable property of powder-in-tube conductors is that there is about 30% void space in the as-drawn wire. We have recently shown that the gas present in the as-drawn Bi-2212 wire agglomerates into large bubbles and that they are presently the most deleterious current limiting mechanism. By densifying short 2212 wires before reaction through cold isostatic pressing (CIPping), the void space was almost removed and the gas bubble density was reduced significantly, resulting in a doubled engineering critical current density (J E ) of 810 A/mm 2 at 5 T, 4.2 K. Here we report on densifying Bi-2212 wire by swaging, which increased J E (4.2 K, 5 T) from 486 A/mm 2 for asdrawn wire to 808 A/mm 2 for swaged wire. This result further confirms that enhancing the filament packing density is of great importance for making major J E improvement in this roundwire magnet conductor. This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Abstract-Bi-2212 round wire is made by the powder-in-tube technique. An unavoidable property of powder-in-tube conductors is that there is about 30% void space in the as-drawn wire. We have recently shown that the gas present in the asdrawn Bi-2212 wire agglomerates into large bubbles and that they are presently the most deleterious current limiting mechanism. By densifying short 2212 wires before reaction through cold isostatic pressing (CIPping), the void space was almost removed and the gas bubble density was reduced significantly, resulting in a doubled engineering critical current density (J E ) of 810 A/mm 2 at 5 T, 4.2 K. Here we report on densifying Bi-2212 wire by swaging, which increased J E (4.2 K, 5 T) from 486 A/mm 2 for as-drawn wire to 808 A/mm 2 for swaged wire. This result further confirms that enhancing the filament packing density is of great importance for making major J E improvement in this round-wire magnet conductor.

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Wires and Tapes

Shen

Jiang

Hellstrom

2015

Digital Encyclopedia of Applied Physics

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Void and phase evolution during the processing of Bi-2212 superconducting wires monitored by combined fast synchrotron micro-tomography and x-ray diffraction

Cited by 45 publications

References 22 publications

Influence of the Oxygen Partial Pressure on the Phase Evolution During Bi-2212 Wire Melt Processing

Influence of the Oxygen Partial Pressure on the Phase Evolution During Bi-2212 Wire Melt Processing

Reduction of Gas Bubbles and Improved Critical Current Density in Bi-2212 Round Wire by Swaging

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