Semiconductor device manufacturing: process – Having superconductive component
Reexamination Certificate
1998-07-09
2001-02-27
Whitehead, Jr., Carl (Department: 2822)
Semiconductor device manufacturing: process
Having superconductive component
C257S662000
Reexamination Certificate
active
06194226
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a junction between superconducting wires which are prepared from oxide high-temperature superconductive materials.
2. Description of the Background Art
In recent years, superconductive materials of ceramics, i.e., oxide superconductors, are watched with interest as those which can exhibit higher critical temperatures. Among such materials, particularly expected for practical application are yttrium, bismuth and thallium based superconductors, which exhibit high critical temperatures of about 90 K, 110 K and 120 K respectively. Such high-temperature superconductive materials may be applied to a cable, a bus bar, a current lead, a coil and the like, and technique for elongation of superconducting wires has been developed.
In application of such high-temperature superconductive materials, it is necessary to obtain long wires having stable properties, as well as to form a junction, which is stabilized and brought into a superconducting state, between such superconducting wires in a state capable of ensuring a heavy current. In particular, a permanent current junction is required in application to a coil. In such a permanent current junction, it is necessary to join superconductors to each other in order to carry a superconducting current.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a stable junction with respect to superconducting wires which are prepared from oxide high-temperature superconductive materials.
Another object of the present invention is to provide a method of manufacturing a stable junction which can carry a superconducting current.
According to one aspect of the present invention, provided is a junction between tape-type superconducting wires formed of metal-coated oxide superconductors, where the superconductors of the superconducting wires which are oppositely joined to each other are overlapped with each other. At the junction, the superconductors forming the superconducting wires must indispensably be joined to each other through no other material.
At the junction, further, the superconductors are overlapped with each other preferably over a length of at least about 5 mm, in order to obtain a stable junction.
According to the present invention, tape-type wires which are formed by covering oxide superconductors with metal coatings are employed as wires of high-temperature superconductors. The material for the metal coatings is preferably unreactive with the high-temperature superconductors, and easily workable. Further, this material preferably has small specific resistance, for serving ass a stabilizer. Such a metal material can be preferably prepared from silver or a silver alloy. Such a material of silver or a silver alloy can be employed as a coating material itself or an intermediate layer for coating. When such a material is applied to an intermediate layer, another metal such as copper, aluminum, nickel, stainless steel or an alloy thereof is further employed as a coating material.
Each oxide superconductor is prepared from a yttrium, bismuth or thallium based super conductor, for example. A bismuth based superconductor is particularly preferable in view of its critical temperature, a high current density, low toxicity and unnecessity for rare earth elements.
In the junction according to the present invention, it is possible to carry a superconducting current since superconductors are overlapped with each other. Such a junction is so stably formed that the same is usefully applied to a permanent current junction of a coil as well as to a junction of a heavy-current conductor.
The junction according to the present invention may be formed through superconducting wires which are so structured that portions of superconductors to be joined are larger in sectional area than other portions. Such structure of superconducting wires can be implemented by increasing the portions to be joined at least in width or thickness as compared with the remaining portions, for example. When superconducting wires of such structure are joined to each other, the junction area as well as the sectional areas of the superconductors are increased at the junction. Even if the amount of the critical current per unit area is slightly reduced at the junction between the superconductors, therefore, the overall amount of the current flowing through the junction is not reduced. Thus, it is possible to prevent the junction from restricting the overall critical current of the as-formed superconducting wire, thereby maintaining a high critical current over the entire wire.
In the junction according to the present invention, the overlapped portions of the superconductors may be covered with a metal. Such a metal may be prepared from the same material as the metal coatings for the superconducting wires, silver or the like, for example. Such a metal cover protects the superconductors against influence by external environment, such as the atmosphere, a cooling medium and the like, for example, and prevents the same from deterioration.
In the junction according to the present invention, end surfaces of the joined superconductors may be inclined at prescribed angles with respect to the cross direction of the superconducting wires, while end surfaces of the metal coatings at the joined portions may be substantially in parallel with the end surfaces of the superconductors or inclined at symmetrical angles thereto. In such a junction, it is possible to define a long boundary surface between the joined superconductors.
In the junction according to the present invention, a plurality of superconducting wires may be overlapped in layers to be joined to another set of a plurality of superconducting wires. In this case, joined portions of the superconducting wires in the respective layers are successively displaced from each other along the longitudinal direction of the superconducting wires.
According to another aspect of the present invention, provided is a junction between tape-type superconducting wires formed of metal-coated oxide superconductors, where the superconductors of the superconducting wires, which are oppositely joined to each other, are overlapped with still another superconductor. The superconductors of the tape-type superconducting wires are overlapped with the still other superconductor preferably over a length of at least about 5 mm. Such a junction is applied when it is difficult to directly join the superconducting wires to each other. At the junction, it is possible to carry a superconducting current since the superconductors are joined to each other. This junction is particularly usefully applied to a permanent current junction of a coil and a junction of a heavy-current conductor.
According to still another aspect of the present invention, provided is a method of joining tape-type superconducting wires formed of metal-coated oxide superconductors, which comprises a step of preparing tape-type superconducting wires having portions to be joined, a step of separating metal coatings from first sides of the superconductors for exposing the superconductors of the superconducting wires in the portions to be joined, a step of overlapping the exposed superconductors with each other, and a step of joining the overlapped superconductors to each other.
The method according to the present invention employs tape-type wires formed by covering oxide superconductors with metal coatings as wires of high-temperature superconductors. The material for the metal coatings is preferably unreactive with the high-temperature superconductors, and easily workable. Further, this material preferably has small specific resistance for serving as a stabilizer. Such a metal material can be preferably prepared from silver or a silver alloy. Such a material of silver or a silver alloy can be employed as the coating material itself or an intermediate layer for coating. When the material is applied to an intermediate layer, another metal such as copper, aluminum, nickel, stainless steel or an alloy there
Kato Takeshi
Mukai Hidehito
Sato Ken'ichi
Shibuta Nobuhiro
Guerrer Maria
Jr. Carl Whitehead
Pennie & Edmonds LLP
Sumitomo Electric Industries Ltd.
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