Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1999-03-08
2001-11-06
Arbes, Carl J. (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C505S739000, C505S740000, C505S741000
Reexamination Certificate
active
06311385
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to high temperature oxide superconducting wires and methods of manufacturing such wires, and more particularly to a high temperature oxide superconducting wire and a method of manufacturing thereof used in such applications as electric power, transportation, high energy, and medical treatment.
2. Description of the Background Art
It has been reported recently that a sintered body of oxide exhibits superconductivity at a high critical temperature, and the technique for superconduction employing such a superconductor is being into practical use. The yttrium-based oxide and the bismuth-based oxide are reported respectively to exhibit the phenomenon of superconduction at 90K and 110K. Such oxide superconductors are expected to be into practical use since they exhibit superconducting properties in liquid nitrogen which is available at a relatively low cost.
In order to transfer alternating current for supplying power, for example, through such superconductors, a superconducting wire formed by coating a superconductor with a silver sheath, coating the silver sheath with an insulator (high-resistant body) and further coating the insulator with metal is employed.
The superconductor is coated with the silver sheath for preventing the crystal structure of the superconductor from being destroyed in the drawing process. The silver sheath is coated with the insulator for reducing the ac loss. The insulator is coated with the metal for providing the superconducting wire with flexibility required.
Superconducting wires having such a structure as set forth above are disclosed in, for example, International Publication No. WO96/28853 and Japanese Patent Laying-Open No. 10-50152.
According to a method disclosed in WO096/28853, a superconductor is surrounded on its periphery by silver or the like, and further surrounded on its periphery by metal. The metal is then oxidized to produce an insulator formed of metal oxide between the silver and metal.
According to a method disclosed in Japanese Patent Laying-Open No. 10-50152, a superconductor is surrounded by silver, and further surrounded on its periphery by electrically resistant alloy (high-resistant body). The resistant alloy is oxidized to produce an insulating oxide between the silver and the resistant alloy.
According to those techniques disclosed in the two publications described above, the metal is oxidized to form the insulating oxide. The oxidation allows the metal to diffuse into the superconductor and accordingly the crystal structure of the superconductor changes. A problem of decrease in the critical current density of the superconducting wire then arises.
SUMMARY OF THE INVENTION
The present invention is made to solve such a problem as described above. One object of the present invention is to provide a high temperature oxide superconducting wire in which metal located on the outer periphery of the superconducting wire does not diffuse into a superconductor to prevent reduction in the critical current density, and a method of manufacturing such a superconducting wire.
According to one aspect of the invention, a high temperature oxide superconducting wire includes a high temperature oxide superconductor, a sheathing body, a high-resistant body, and a coating body. The sheathing body is formed of a material containing silver to coat the high temperature oxide superconductor. The high-resistant body is formed of a material containing a heat-resistant oxide ceramics to coat the sheathing body. The coating body is formed of a material which is inactive relative to the high-resistant body in a high temperature oxidative atmosphere to coat the high-resistant body.
In the high temperature oxide superconducting wire having such a structure, the high-resistant body and the coating body are inactive relative to each other in the high temperature oxidative atmosphere, that is, the high-resistant body and the coating body are difficult to react with each other in that atmosphere. Consequently, it is possible to prevent the material constituting the coating body from diffusing into the high temperature oxide superconductor in a heat treatment process. The crystal structure of the high temperature oxide superconductor does not change and reduction in the critical current density can be restricted.
Preferably a plurality of sheathing bodies are provided and the high-resistant bodies are interposed between the plurality of sheathing bodies respectively. Accordingly, the ac loss can be decreased when alternating current is transferred.
The high temperature oxide superconductor is preferably in the shape of filament.
The heat-resistant oxide ceramics is preferably a ceramic material which is stable in an oxidative atmosphere of at least 800° C.
Preferably the heat-resistant oxide ceramics includes at least one selected from the group consisting of Al
2
O
3
, MgO, CoO, Co
3
O
4
, SiO
2
, Bi
2
Sr
2
CuOx and (Sr, Ca)
2
CuO
3
.
The material constituting the coating body preferably includes at least one selected from the group consisting of silver, silver alloy, oxide-dispersed silver, stainless steel, and nickel alloy. “Oxide-dispersed silver” herein refers to the metal silver in which oxide grains are dispersed.
Preferably the silver alloy includes at least one selected from the group consisting of Ag—Mg alloy, Ag—Mn alloy, Ag—Au alloy, Ag—Sb alloy, and Ag—Pd alloy.
Preferably the oxide-dispersed silver is formed of silver in which oxide grains including at least one selected from the group consisting of Al
2
O
3
, MgO, Mn
2
O
3
and Li
2
O are dispersed. The oxide-dispersed silver is represented as [Ag—Al
2
O
3
] that refers to metal silver in which alumina (Al
2
O
3
) grains are uniformly dispersed. This representation is hereinafter similarly employed.
Preferably the stainless steel is SUS304 (Japanese Industrial Standard or SUS310 (Japanese Industrial Standard).
Preferably the nickel alloy is Ni—Cr—Fe alloy.
Preferably conductive metal is added to the heat-resistant oxide ceramics.
Preferably the conductive metal includes at least one selected from the group consisting of silver, silver alloy, gold, and gold alloy.
The material forming the sheathing body preferably includes at least one selected from the group consisting of Ag, Ag—Au alloy and Ag—Sb alloy.
The high temperature oxide superconductor is preferably Bi (Pb)—Sr—Ca—Cu—O-based high temperature superconductor.
Preferably such a high temperature oxide superconducting wire as described above is a high temperature oxide superconducting current lead.
According to one aspect of the present invention, a method of manufacturing a high temperature oxide superconducting wire includes the steps of filling a first pipe formed of a material containing silver with raw powder which becomes a high temperature oxide superconductor by a heat treatment or with powder of a high temperature oxide superconductor, placing the first pipe filled with the raw powder or the powder of the high temperature oxide superconductor in a second pipe, filling a space between an outer surface of the first pipe and an inner surface of the second pipe with heat-resistant oxide ceramic powder. The second pipe is formed of a material which is inactive relative to the heat-resistant oxide ceramic powder in a high temperature oxidative atmosphere. The method of manufacturing the high temperature oxide superconducting wire further includes a step of applying a plastic working and a heat treatment to the second pipe filled with the heat-resistant oxide ceramic powder.
According to the method of manufacturing the high temperature oxide superconducting wire following those steps, since the second pipe is inactive relative to the heat-resistant oxide ceramic powder in the high temperature oxidative atmosphere, that is, the second pipe is difficult to react with the ceramic powder in that atmosphere, the material constituting the second pipe is never diffused into the raw powder or the powder of the high temperature oxide superconductor within th
Hayashi Kazuhiko
Ueyama Munetsugu
Arbes Carl J.
Foley & Lardner
Sumitomo Electric Industries Inc.
LandOfFree
High temperature oxide superconducting wire and method of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with High temperature oxide superconducting wire and method of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and High temperature oxide superconducting wire and method of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2617847