From a search of 1998 and 1999 ( June 1) patents- here is just an example how 200 new Patents are important to SC and the FUTURE:
164.195.100.11
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='high+temperature'&s2=superconductors&OS=
"high+temperature"+AND+superconductors&RS="high+temperature"+AND
+superconductors
( 50 ) Yet is my read this and others- EVEN SUMO. Elecrtric of Japan has a nice product for WIRES, yet it is OXIDE BASED,
but with our DUST and Diamonds we can change the
mattrix for better-smarter-faster applications-
Diamonds are Hard, Oxide is RUSTY! NUKE has it all over them...
and other is the future:
TEXT: In recent years, attention is directed to ceramics based, i.e. oxide based, superconductors as the superconductive material
having a higher critical temperature. Particularly, yttrium, bismuth, and thallium based superconductors having high critical
temperatures of 90K, 110K, and 120K, respectively, show practical usage potential.
The applicability of these high temperature superconductive materials to cables, bus bars, current leads, coils and the like
have been considered, taking the approach of elongating the superconductive material for these applications.
A known method of obtaining an elongated oxide superconducting wire includes the steps of covering material powder with a
metal sheath and applying thermal treatment for turning the material powder into a superconductor to result in a wire of a
superconductor covered with a metal sheath.
There is another approach of manufacturing a wire having a plurality of oxide high temperature superconductor filaments,
similar to conventional metal based and compound based superconductors.
Not only high critical temperature, but also high critical current density is required to apply high temperature superconducting
wires to cables and magnets. High temperature superconducting wires must maintain the required critical current density in
the used magnetic field, and even under practical usage circumstances where it is bent at a predetermined curvature after being
subjected to thermal treatment. In view of the foregoing, a high temperature superconducting wire is desired that does not
have critical current density reduced even after being subjected to bending work.
SUMMARY OF THE INVENTION
RE:<<high critical current density is required to apply high temperature superconducting
wires to cables and magnets...>> STRESS DIAMONDS are denser. Chuckanotdense,big,not dense like a Market Maker.
United States Patent
5,869,430
Mukai , et al.
February 9, 1999
High temperature superconducting wire using oxide superconductive material
Abstract
According to an aspect, a tape-type high temperature superconducting wire is provided by applying compression work to a
wire manufactured by drawing so that an oxide high temperature superconductor is divided into a plurality of
superconductors by a stabilizing material of substantially equal thickness. According to another aspect, a high temperature
superconducting wire is provided by packing a material which becomes a superconductor portion into a metal sheath which
becomes the stabilizing material and applying drawing work thereto, followed by bundling an assembly of these wire in a metal
sheath and applying drawing work thereto. The thickness of the superconductor portion is approximately 10% or less than the
thickness of the wire. The critical current density is hardly decreased in the high temperature superconducting wire even if
subjected to bending work.
Inventors:
Mukai; Hidehito (Osaka, JP); Sato; Kenichi (Osaka, JP); Shibuta; Nobuhiro (Osaka, JP)
Assignee:
Sumitomo Electric Industries, Ltd. (JP)
Appl. No.:
479898
Filed:
June 7, 1995
U.S. Class:
505/230; 505/231; 505/232;
References Cited [Referenced By]
U.S. Patent Documents
4849288
Jul., 1989
Schmaderer et al.
428/368.
5017553
May., 1991
Whitlow et al.
505/1.
5104849
Apr., 1992
Shiga et al.
428/688.
5132278
Jul., 1992
Stevens
505/704.
5151406
Sep., 1992
Sawada et al.
428/688.
Foreign Patent Documents
0 283 312 A2
Sep., 1988
EP.
0305820
Mar., 1989
EP.
0311337
Apr., 1989
EP.
0 358 779
Mar., 1990
EP.
0 357 779
Mar., 1990
EP.
0 397 943 A1
Nov., 1990
EP.
0 449 316
Oct., 1991
EP.
Other References
Wilhelm et al., "Praparation und Eigenschaffen von Silberbandleitem mit Kern aus B(P)SCCO 11OK-Phase,"
Supraleitung und Teiftemperaturkechnik: for the Status Seminar Feb. 25-27, 1991; pp. 400-403.
Sekine et al., "Metallurgical Studies and Optimization of Critical Current Density in Bi-(Pb)-Sr-Ca-Cu-O
Superconductors," Japanese Journal of Applied Physics, vol. 28, No. 7, Jul. 1989, pp. 1185-1188.
Wada et al., "Strain Effects in Oxide Superconductors," ICMC '90 Topical Conference on Materials Aspects
of High Temperature Superconductors, May 1990, pp. 1011-1016.
Seido et al, "Fabrication and Characteristics of Multi-core T1-Ba(Sr)-Ca-Cu Oxide Superconducting Tapes,"
Advances in Superconductivity II ›Proceedings of the 2nd International Symposium on Superconductivity ISS
'89), Nov. 14-17, 1989, Tsukuba, Japan, pp. 401-404.
Mukai et al., "Properties of Ag/Bi-Based Superconducting Long Wire and Test Coil," Advances in
Superconductivity III ›Proceedings of the 3rd International Symposium on Superconductivity (ISS '90!, Nov.
6-9, 1990, Sendai, Japan, pp. 607-612.
Geballe, "Paths to Higher Temp. Supercond" Science vol. 259, Mar. 12, 1993 pp. 1550-1551.
"Cuprate Superconductors" May 10, 1993 C & EN, pp. 4-5.
Primary Examiner: Yamnitzky; Marie
Attorney, Agent or Firm: Pennie & Edmonds LLP
Parent Case Text
This is a continuation of application Ser. No. 08/178,345, filed Jan. 06, 1994, now abandoned, which is a continuation of
application Ser. No. 07/854,134, filed Mar. 19, 1992, now abandoned.
Claims
1. A superconducting tape, comprising:
a plurality of oxide superconductor filaments, and
a continuous stabilizing matrix of noble metal or noble metal alloy enclosing each of said plurality of oxide superconductor
filaments,
wherein each of said plurality of filaments has a ribbon shape,
wherein said plurality of filaments are uniformly distributed in the cross section of said superconducting tape,
wherein said stabilizing matrix has substantially equal thickness between each of said filaments,
wherein each of said filaments has a thickness of not more than about 10% of the thickness of said superconducting tape, and
wherein the critical current density of said tape remains at least 85% of the original when being subjected to a bending strain of
0.3% for 20 times.
2. The superconducting tape in accordance with claim 1, wherein said tape has at least 36 filaments.
3. The superconducting tape in accordance with claim 1, wherein said tape has a critical current density of between about
16,200 and 18,300 A/cm.sup.2 at liquid nitrogen temperature after being subjected to the bending strain.
4. The superconducting tape in accordance with claim 1, wherein said oxide superconductor is selected from the group
consisting of bismuth based oxide superconductors and thallium based oxide superconductors.
5. A superconducting wire, comprising:
a plurality of oxide superconductor filaments, and
a continuous stabilizing matrix of noble metal or noble metal alloy enclosing each of said plurality of oxide superconductor
filaments,
wherein said plurality of filaments are uniformly distributed in the cross section of said superconducting wire, said stabilizing
matrix has substantially equal thickness between each of said filaments,
wherein each of said filaments has a thickness of not more than about 10% of the thickness of said superconducting wire, and
wherein the critical current density of said wire remains about 90% or more of the original after being subjected to a bending
strain of 0.5%.
6. The superconducting wire in accordance with claim 5, wherein said wire has at least 36 filaments.
7. The superconducting wire in accordance with claim 5 wherein said wire maintains at least 92% of the original critical current
density after being subjected to a bending strain of 0.3%.
8. The superconducting wire in accordance with claim 5, wherein said wire has a critical current density of between about
15,000 and 17,900 A/cm.sup.2 at liquid nitrogen temperature after being subjected to the bending strain.
9. The superconducting wire in accordance with claim 5, wherein said oxide superconductor is selected from the group
consisting of bismuth based oxide superconductors and thallium based oxide superconductors.
10. A superconducting wire, comprising:
a plurality of oxide superconductor filaments, and
a continuous stabilizing matrix of noble metal or noble metal alloy enclosing each of said plurality of oxide superconductor
filaments,
wherein said plurality of filaments are uniformly distributed in the cross section of said superconducting wire, said stabilizing
matrix has substantially equal thickness between each of said filaments,
wherein each of said filaments has a thickness of not more than about 10% of the thickness of said superconducting wire, and
wherein said wire maintains at least 82% of the original critical current density after being subjected to a bending strain of 0.3%
for 200 times.
11. The superconducting wire in accordance with claim 10, wherein said wire has a critical current density of between about
14,100 and 16,400 A/cm.sup.2 at liquid nitrogen temperature after being subjected to the bending strain.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a high temperature superconducting wire using oxide high temperature superconductive
material, and more particularly, to a multifilamentary superconducting wire that can maintain a high critical current density
applicable to magnets, cables, etc.
2. Description of the Background Art
In recent years, attention is directed to ceramics based, i.e. oxide based, superconductors as the superconductive material
having a higher critical temperature. Particularly, yttrium, bismuth, and thallium based superconductors having high critical
temperatures of 90K, 110K, and 120K, respectively, show practical usage potential.
The applicability of these high temperature superconductive materials to cables, bus bars, current leads, coils and the like
have been considered, taking the approach of elongating the superconductive material for these applications.
A known method of obtaining an elongated oxide superconducting wire includes the steps of covering material powder with a
metal sheath and applying thermal treatment for turning the material powder into a superconductor to result in a wire of a
superconductor covered with a metal sheath.
There is another approach of manufacturing a wire having a plurality of oxide high temperature superconductor filaments,
similar to conventional metal based and compound based superconductors.
Not only high critical temperature, but also high critical current density is required to apply high temperature superconducting
wires to cables and magnets. High temperature superconducting wires must maintain the required critical current density in
the used magnetic field, and even under practical usage circumstances where it is bent at a predetermined curvature after being
subjected to thermal treatment. In view of the foregoing, a high temperature superconducting wire is desired that does not
have critical current density reduced even after being subjected to bending work.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a high temperature superconducting wire in which reduction of critical
current density is suppressed even when subjected to bending strain.
Another object of the present invention is to provide a bending worked high temperature superconducting wire that has a
sufficient high critical current density, and that has practical applicability to cables, bus bars, current leads, coils, and the like.
According to an aspect of the present invention a tape-type high temperature superconducting wire, having a high
temperature superconductor formed of oxide high temperature superconducting material arranged in a stabilizing material is
provided, in which the tape-type wire is formed by applying compressive load to a wire manufactured by drawing so that a
high temperature superconductor is divided into a plurality of superconductors by a stabilizing material of substantially equal
thickness.
According to another aspect of the present invention, a high temperature superconducting wire having a high temperature
superconductor formed of oxide superconductive material arranged in a stabilizing material is provided, in which the wire is
manufactured by drawing so that a high temperature superconductor is divided into a plurality of superconductors by a
stabilizing material of substantially equal thickness.
The high temperature superconducting wire of the above aspects can be manufactured by preparing a plurality of wires
having an oxide high temperature superconductor covered with a stabilizing material of equal thickness, bundling these wires
within a metal sheath, and applying plastic working thereto. The high temperature superconducting wire can be manufactured
by preparing a stabilizing material having a plurality of communicating holes formed at equal spacing, forming an oxide high
temperature superconductor in the plurality of holes in the stabilizing material, and then applying plastic working thereto.
In the above-described aspects, the thickness of respective divided high temperature superconductors preferably is
approximately 10% or less than the thickness of the high temperature superconducting wire.
In this specification, the term "thickness" means the size in the cross-sectional direction of a linear product. The term
"thickness" refers to the commonly used meaning of thickness in a tape-type wire, and refers to the diameter in a wire having a
substantially circular cross-section.
In the above-described aspects, the high temperature superconducting wire where the thickness of each divided high
temperature superconductor is approximately 10% or less than the thickness of the wire can be processed so as to have a
bending strain of 0.3% or below. A high temperature superconducting wire subjected to bending work with a bending strain
of 0.3% or below maintains a critical current density close to that prior to being worked.
In the specification, "bending strain" is defined as follows: ##EQU1##
In the above-described aspects, the high temperature superconducting wire where the thickness of the divided high
temperature superconductor is approximately 10% or less than the thickness of the wire may preferably be applied to a wire
that is bent at a bending strain of 0.3% or below. This wire comprises cables, bus bars, and current leads.
The stabilizing material according to the present invention is unreactive to high temperature superconductors, and is
preferably easily processed. The stabilizing material includes silver, silver alloy, etc.
In the present invention, yttrium, bismuth, and thallium based oxide superconductors are used as the high temperature
superconductor. A bismuth based high temperature superconductor is more preferable because of its high critical
temperature, high critical current density, low toxicity and unnecessity of rare earth elements.
The superconducting wire using an oxide superconducting material is desired to be processed in a tape-type manner to
increase the critical current density. A tape-type high temperature superconducting wire can be bent at a small bending
diameter since it is thin in comparison with a wire of round configuration. A tape-type wire is particularly applicable to coils
and the like.
A wire having a high temperature superconductor divided into a plurality of superconductors by a stabilizing material of
substantially equal thickness is compression-worked to provide a tape-type wire where the thickness of the high
temperature superconductor is substantially constant. A wire having high temperature superconductors distributed at a
constant distance exhibits a high critical current density with almost no decrease in the density even when subjected to bending
work.
If the thickness of the stabilizing material surrounding the high temperature superconductor is not constant, the thickness of the
high temperature superconductor after the work process will be uneven because of local difference of levels in receiving the
compression work. A partially thinned superconductor may limit the critical current value of the entire wire. This variation
degrades the critical current density of the high superconducting wire. A partially thickened superconductor provides a greater
strain to the wire at the time of its bending work.
According to a further aspect of the present invention, a high temperature superconducting wire having a plurality of
superconductor portions formed of an oxide high temperature superconductive material arranged in a stabilizing material is
provided, which is formed by filling a metal sheath serving as the stabilizing material with a material which becomes the
superconductor portion and applying drawing work thereto, followed by bundling an assembly of these wires in a metal sheath
and applying drawing work thereto, in which the thickness of each superconductor is 10% or less than the thickness of the
entire wire.
A multifilamentary superconducting wire according to the present aspect can be obtained by covering powder of an oxide
high temperature superconductor or powder of a precursor with a metal sheath such as of silver to form a round wire by
drawing, followed by gathering a plurality of these wires to be covered with a metal sheath such as of silver and applying
drawing work thereto. If necessary, the wire may be subjected to compression process such as rolling to result in a tape-type
configuration, or may be sintered by thermal treatment under the round configuration.
The multifilamentary superconducting wire is preferably metal-covered from the standpoint of stability. This metal preferably
does not react with high temperature superconductors, can be easily processed, and has a low specific resistivity so as to
serve as a stabilizing material. Such a metal comprises, for example, silver and silver alloy.
The metal covering may be used as an intermediate layer. In this case, another metal, such as copper, aluminum, or an alloy
thereof, is covered over the intermediate layer.
By establishing the thickness of the high temperature superconductor to a thickness of approximately 10% or less than the
thickness of the wire, reduction of critical current density can be maintained within a practical range even if the wire is bent at a
bending strain of, for example, 0.3%. In the wire according to the present invention, the superconductor portion comprises a
fine filament, for example a filament having a thickness of several .mu.m-50 .mu.m. If the thickness of the superconductor
exceeds 10% of the thickness of the wire, decrease in critical current density by bending becomes significant. More preferably,
the decrease of critical current density by bending can further be suppressed by making the thickness of the superconductor
5% or less than the thickness of the wire.
The multifilamentary superconducting wire according to the present aspect is formed by bundling only once, strands having an
oxide superconductor covered with a metal. In this wire, the distance between the superconductors is substantially constant
so that the critical current density is high.
The number of strands to be bundled is preferably at least 30 in the normally used size so that the ratio of the oxide
superconductor to the metal covering is not lowered.
The multifilamentary superconducting wire according to the present aspect can include at least a portion which is subjected to
bending work to have a bending strain of 0.3% or below. This multifilamentary superconducting wire having a bending strain of
0.3% or below has reduction of the critical current density suppressed.
The multifilamentary superconducting wire can preferably be used for the steps of winding and unwinding under a condition of
a bending strain of 0.3% or below. Degradation of the superconductive characteristic of a wire can be prevented within a
range of a bending strain of 0.3% or below.
The multifilamentary superconducting wire can be wound around a reel or a drum under the tape-type wire configuration to be
used for cables or coils. In winding, a bending strain of 0.3% or below gives the advantage of maintaining a high critical current
density and providing a wire for practical usage. The multifilamentary superconducting wire can be applied to various wires that
are worked at a bending strain of 0.3% or below.
According to a further aspect of the present invention, a method is provided for manufacturing a high temperature
superconducting wire of multifilaments, including the steps of: preparing a plurality of strands having an oxide superconductor
covered with a first metal sheath; bundling the plurality of strands to be packed in a second metal sheath so that each
multifilamentary oxide superconductor is separated by a metal sheath material of substantially equal thickness; applying at least
once, plastic working to exert compressive load towards the sectional direction of the second metal sheath having the plurality
of strands packed therein.
In the method according to the present invention, the plastic working includes the steps of drawing and applying compressive
load. When a round wire is to be obtained, drawing work is employed. When a flat tape-type wire is to be obtained, drawing,
and then compression load is applied.
The method according to the present invention preferably includes the step of thermal treatment after the plastic working. In
this case, it is further preferable that the working process and the thermal treatment are repeated several times.
In the method according to the present invention, it is possible to control the thickness of the oxide superconductor of the
wiring obtained in the plastic working step by changing the number of strands packed in the second metal sheath. The
thickness of the superconductor is preferably made to be 10% of the thickness of the wire.
In the method according to the present invention, the plurality of strands are bundled only once so that the oxide
superconductors are spaced by the metal sheath material of substantially equal thickness. The strands bundled once gives the
advantage of yielding a multifilamentary superconducting wire having superconductors of equal thickness distributed uniformly
on the cross-section thereof. Such a multifilamentary wire maintains relatively high critical current density even if bending work
is applied.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from
the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional view of a wire after drawing work is applied according to a first embodiment of the present invention.
FIG. 2 is a sectional view of a wire after drawing work is applied according to a second embodiment of the present invention.
FIG. 3 is a sectional view of a wire after drawing work is applied of a conventional example.
FIG. 4 is a sectional view showing a tape-type wire where the wire after drawing of the second embodiment of the present
invention is subjected to rolling work.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Oxides or carbonates including appropriate elements were mixed to have a composition of
Bi:Pb:Sr:Ca:Cu=1.79:0.43:1.99:2.22:3.0 |
