Overpressure processing of Ag-sheathed Bi-2212 tapes

Reeves, J.; Polák, M.; Zhang, W.; Hellstrom, E. E.; Babcock, S.E.; Larbalestier, D.C.; Inoue, Naomi; Okada, Minoru

doi:10.1109/77.620867

Cited by 10 publications

(1 citation statement)

References 3 publications

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“…In contrast, cold isostatic pressing (CIPping), swaging, and hot isostatic pressing (HIPping) are densification techniques that keep the round conductor shape. Overpressure processing (OP) is a modified HIPping with gas flowing for better oxygen partial pressure control [21,22]. It has been very successful for processing Bi-2223 tapes [23][24][25], and is used by Sumitomo Electric for manufacturing Bi-2223 conductor [25].…”

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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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