Fabrication of 90-m length Bi2Sr2CaCu2O8 + x Ag-sheathed superconducting tapes

Haugan, Timothy J.; Pitsakis, M.; Ye, J.; Wong, F.; Patel, S.; Shaw, D.T.

doi:10.1016/0964-1807(95)00036-5

Cited by 10 publications

(3 citation statements)

References 6 publications

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“…In the case of Bi-2212 tape conductor, one of major causes of low J E in long-length Bi-2212 was suggested to be high internal gas pressures at high temperatures [19][20][21][22][23]. Internal gases may include residual air and humidity present in as-drawn wires, gases released as a result of contaminants adsorbed on powder surfaces [24] and solid remnants in powder gasifying upon heating.…”

Section: Introductionmentioning

confidence: 99%

Role of internal gases and creep of Ag in controlling the critical current density of Ag-sheathed Bi2Sr2CaCu2Ox wires

Shen

Ghosh

Cooley

et al. 2013

Journal of Applied Physics

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High engineering critical current density J E of >500 A/mm 2 at 20 T and 4.2 K can be regularly achieved in Ag-sheathed multifilamentary Bi 2 Sr 2 CaCu 2 O x (Bi-2212) round wire when the sample length is several centimeters. However, J E (20 T) in Bi-2212 wires of several meters length, as well as longer pieces wound in coils, rarely exceeds 200 A/mm 2 . Moreover, long-length wires often exhibit signs of Bi-2212 leakage after melt processing that are rarely found in short, open-end samples. We studied the length dependence of J E of state-of-the-art powder-in-tube (PIT) Bi-2212 wires and gases released by them during melt processing using mass spectroscopy, confirming that J E degradation with length is due to wire swelling produced by high internal gas pressures at elevated temperatures [1,2]. We further modeled the gas transport in Bi-2212 wires and examined the wire expansion at critical stages of the melt processing of as-drawn PIT wires and the wires that received a degassing treatment or a colddensification treatment before melt processing. These investigations showed that internal gas pressure in long-length wires drives creep of the Ag sheath during the heat treatment, causing wire to expand, lowering the density of Bi-2212 filaments, and therefore degrading the wire J E ; the creep rupture of silver sheath naturally leads to the leakage of Bi-2212 liquid. Our work shows that proper control of such creep is the key to preventing Bi-2212 leakage and achieving high J E in long-length Bi-2212 conductors and coils.

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Section: Introductionmentioning

confidence: 99%

Role of internal gases and creep of Ag in controlling the critical current density of Ag-sheathed Bi2Sr2CaCu2Ox wires

Shen

Ghosh

Cooley

et al. 2013

Journal of Applied Physics

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“…The development and optimization of the powder-intube (PIT) and subsequent thermo-mechanical processes have made production of high J c tapes easier. During the fabrication process the superconductor wires or tapes undergo mechanical deformation and thermal treatment [2][3][4][5].…”

Section: Introductionmentioning

confidence: 99%

“…A thin layer of superconductor next to the silver sheath is reported to be responsible for the transport current. This 4 Author to whom correspondence should be addressed. is due to the good grain alignment obtained in the thin layer [6,7].…”

Section: Introductionmentioning

confidence: 99%

Intrinsic deformation behaviour in pressed Bi-Sr-Ca-Cu-O tapes

Cooper

Gao

et al. 2001

Supercond. Sci. Technol.

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It was reported that the critical current density of superconducting tapes can be improved using cryogenic processing. The present paper studies the intrinsic grain alignment characteristics of cryogenically pressed and room-temperature-pressed Bi-Sr-Ca-Cu-O tapes. The grain alignment mechanisms of the two processed tapes were found to be different. The cryogenically pressed tapes showed a step-like increase in grain alignment at approximately 30% deformation, while the increase in grain alignment for the room-temperature-pressed tapes was gradual. The results indicate that the behaviour is reproducible and independent of annealing time and therefore, intrinsic to the deformation steps of each process. The effects of deformation on the alignment are suggested to occur due to two factors:(1) the point at which fracturing of the grains occurs and (2) rotation or movement of these grains into the preferred alignment. The differences observed between the two processes are due to the combined effects of these two factors. The significance of this study is that better grain alignment can be achieved in cryogenically pressed tapes at lower deformation ratios.

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