Superconductor technology: apparatus – material – process – High temperature devices – systems – apparatus – com- ponents,... – Superconducting wire – tape – cable – or fiber – per se
Reexamination Certificate
2001-04-26
2002-10-15
Elve, M. Alexandra (Department: 1725)
Superconductor technology: apparatus, material, process
High temperature devices, systems, apparatus, com- ponents,...
Superconducting wire, tape, cable, or fiber, per se
C505S234000, C505S236000, C505S238000
Reexamination Certificate
active
06466805
ABSTRACT:
TECHNICAL FIELD
This invention relates to composite superconductors and more particularly to Bi-2223 superconductors surrounded by other superconducting materials.
BACKGROUND OF THE INVENTION
The powder-in-tube (PIT) process, which yields a highly textured (Bi, Pb)
2
Sr
2
Ca
2
Cu
3
O
y
(Bi-2223) superconductor with its c-axis aligned parallel to the tape surface, is an industrially scalable technique for fabricating long-length superconductors. In zero applied magnetic field, the critical current density (J
c
) of superconducting tape is controlled by its microstructure. Grain boundaries act as barriers to the transfer of transport current between grains. The crystallographic anisotropy of Bi-2223, which exhibits a micaceous or platelike morphology, allows large contact areas alignment of grains with their c-axis perpendicular to the rolling direction of the tape, easy transfer of current across its grain boundaries, and high J
c
values. The fabrication of YBa
2
Cu
3
O
7-&dgr;
(Y-123) wires by the PIT technique has not been successful because of YBCO's granularity. Y-123 exhibits greater isotropy than Bi-2223 and its intergranular transport current is poor because of weak links. In an applied magnetic field, Y-123 shows much better J
c
response than Bi-2223 and the irreversibility line (IRL) of high-T
c
materials can provide insight into materials limitations for various applications.
Recent progress in growing single crystals of Bi-2223 provided an opportunity to study its IRL line. A sharp irreversibility field (H*) drop was observed between 20 and 40 K. At 75 K, H* was only ≈0.3 T. This observation clearly shows very weak intrinsic pinning in Bi-2223 single crystals. Intrinsic pinning in Y-123 single crystal is sufficiently strong to keep H* at 77 K to ≈8 T. Using ion-beam-assisted deposition (IBAD), c-axis-oriented Y-123 thin films have been deposited on polycrystalline metallic tapes buffered with yttria stabilized zirconia (YSZ). A significant improvement of the in-plane texture led to a high J
c
above 10
6
(A/cm
2
).
Another method of depositing thin films is called rolling-assisted biaxial textured substrates (RABiT). A biaxially textured nickel substrate was aligned to within a few degrees.
Epitaxial growth of oxide buffer layers on the substrate made possible the growth of Y-123 films that were 1.5 &mgr;m thick and exhibited superconducting properties comparable to those observed for epitaxial films on single-crystal substrates. The transport current density as a function of temperature and applied magnetic field of Bi-2223/Ag wires and tapes, show that practical applications are limited to either low temperature and high magnetic field ≈20 K and ≈10 T or high temperature and low magnetic field ≈77K and less than 0.5 T.
BRIEF SUMMARY OF THE INVENTION
It is a general object of the invention to combine the good alignment of Bi-2223 grains in Ag-sheathed superconducting tapes to obtain high J
c
values at high temperature and low field, and the good intrinsic pinning of Y-123 thin film in order to maintain high J
c
values in high fields.
Another object of the present invention is to provide a new composite tape in which the primary function of a central Ag-sheathed (Bi,Pb)
2
Sr
2
Ca
2
Cu
3
O
y
(Bi-2223) filaments was to conduct transport current, with a YBa
2
Cu
3
O
7-&dgr;
(Y-123) thin films deposited on the Ag-sheathed Bi2223 tape to shield the applied magnetic field and protect the central Bi-2223 filaments.
Yet another object of the invention was to obtain critical current densities of the Y-123-coated, Ag sheathed Bi-2223 tapes which were better than those of an uncoated tape.
Still other aspects of the invention was that the Y-123 thin film exhibited a T
c
≈72K and a broad transition region that shifted the effect to lower temperatures. Pole figure measurements showed widely spread a,b planes along the rolling direction, indicating high-angle grain boundaries that diminished the magnitude of the effect. Microstructural observations showed platelike grains of Y-123 with fine growth ledges in the thin film that was heat treated, in contrast with the microstructure of an as-coated thin film that showed large twinned grains. The experimental results showed that heat treating Y-123 thin film according to the previously known Bi-2223 tape schedule was compatible with an beneficial for Y-123.
REFERENCES:
patent: 4952554 (1990-08-01), Jin et al.
patent: 5151406 (1992-09-01), Sawada et al.
patent: 5504058 (1996-04-01), Tanaka et al.
patent: 5874384 (1999-02-01), Balachandran et al.
patent: 5908812 (1999-06-01), Cotton et al.
patent: 5952614 (1999-09-01), Ries
patent: 6038462 (2000-03-01), Snitchler et al.
patent: 6069116 (2000-05-01), Li et al.
patent: 6205345 (2001-03-01), Sato et al.
patent: 6305070 (2001-10-01), Masur et al.
patent: 6313408 (2001-11-01), Fujikami et al.
patent: 6393690 (2002-05-01), Snitchler et al.
Balachandran Uthamalingam
Eror Nicholas G.
Lelovic Milan
Cooke Colleen P.
Elve M. Alexandra
Emrich & -Dithmar
The University of Chicago
LandOfFree
Shielded high-Tc bscco tapes or wires for high field... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Shielded high-Tc bscco tapes or wires for high field..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Shielded high-Tc bscco tapes or wires for high field... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2976477