Metallurgy, fabrication, and superconducting properties of multifilamentary Nb/sub 3/Al composites
The control of metallurgical structure during fabrication that will improve the superconducting properties of multifilamentary, aluminium-stabilized, Nb/sub 3/Al composites is described. Composites are fabricated by placing niobium rods in an aluminum matrix, and then drawing to wire. Nb/sub 3/Al is formed at temperatures exceeding 1800/sup 0/C for about 5 s and ordered at 750/sup 0/C for 48 h. A critical current, J/sub c/(H), in excess of 10/sup 5/ A/cm/sup 2/ (F/sub p/ approximately equal to 7 x 10/sup 8/ dynes/cm/sup 3/) at 7 T and a T/sub c/ to 18.2 K are obtained. Attempts to improve J/sub c/(H) by controlling the grain size in the Nb/sub 3/Al diffused layer are discussed. Precipitates, arising from the addition of carbon during Nb/sub 3/Al layer growth, do not appear to be effective as grain-boundary or flux pinners. When 1 percent Zr is added to the Nb, the growth of the Nb/sub 3/Al layer is accelerated, T/sub c/ is lowered and J/sub c/(H) is not significantly improved. J/sub c/(H) rapidly decreases with an increase in Nb/sub 3/Al or (Nb-Zr)/sub 3/Al layer thickness, d. J/sub c/(H) is independent of d in composites with d greater than or approximately equal to 1.5 ..mu..m. In general, the Nb/sub 3/Al grain size appears comparable to d for d less than or equal to 1 ..mu..m. Significant improvement of J/sub c/(H) for Nb/sub 3/Al superconducting composites reacted at temperatures above 1800/sup 0/C (to achieve T/sub c/ greater than 17 K) is achieved only by maintaining the layer thickness well below d approximately equal to 1.0 ..mu..m.
- Research Organization:
- Argonne National Lab., IL (USA)
- DOE Contract Number:
- W-31-109-ENG-38
- OSTI ID:
- 7230932
- Report Number(s):
- CONF-760829-51; TRN: 77-006321
- Resource Relation:
- Conference: Applied superconductivity conference, Stanford, CA, USA, 17 Aug 1976
- Country of Publication:
- United States
- Language:
- English
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SUPERCONDUCTIVITY AND SUPERFLUIDITY
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