GB2294802A - Superconducting composites and method of production - Google Patents
Superconducting composites and method of production Download PDFInfo
- Publication number
- GB2294802A GB2294802A GB9520742A GB9520742A GB2294802A GB 2294802 A GB2294802 A GB 2294802A GB 9520742 A GB9520742 A GB 9520742A GB 9520742 A GB9520742 A GB 9520742A GB 2294802 A GB2294802 A GB 2294802A
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- GB
- United Kingdom
- Prior art keywords
- metal
- superconducting
- precursor
- particles
- silver
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- 239000002131 composite material Substances 0.000 title claims abstract description 22
- 238000000034 method Methods 0.000 title claims description 26
- 238000004519 manufacturing process Methods 0.000 title claims description 8
- 229910052751 metal Inorganic materials 0.000 claims abstract description 40
- 239000002184 metal Substances 0.000 claims abstract description 40
- 238000012545 processing Methods 0.000 claims abstract description 22
- 239000002243 precursor Substances 0.000 claims abstract description 18
- 239000000919 ceramic Substances 0.000 claims abstract description 14
- 239000011159 matrix material Substances 0.000 claims abstract description 14
- 239000002923 metal particle Substances 0.000 claims abstract description 14
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 claims abstract description 12
- 239000000843 powder Substances 0.000 claims abstract description 12
- 229910052709 silver Inorganic materials 0.000 claims abstract description 11
- 239000004332 silver Substances 0.000 claims abstract description 11
- 239000002245 particle Substances 0.000 claims abstract description 7
- 239000003054 catalyst Substances 0.000 claims abstract description 4
- 229910001316 Ag alloy Inorganic materials 0.000 claims description 5
- 238000005096 rolling process Methods 0.000 claims description 5
- 239000002887 superconductor Substances 0.000 abstract description 18
- 229910000657 niobium-tin Inorganic materials 0.000 abstract description 2
- 239000000956 alloy Substances 0.000 abstract 1
- 229910045601 alloy Inorganic materials 0.000 abstract 1
- 229910052797 bismuth Inorganic materials 0.000 abstract 1
- 150000001875 compounds Chemical class 0.000 abstract 1
- 229910052716 thallium Inorganic materials 0.000 abstract 1
- 238000007796 conventional method Methods 0.000 description 3
- 239000012467 final product Substances 0.000 description 2
- 229910001092 metal group alloy Inorganic materials 0.000 description 2
- 150000002739 metals Chemical class 0.000 description 2
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 description 1
- 229910000416 bismuth oxide Inorganic materials 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000010348 incorporation Methods 0.000 description 1
- 229910000765 intermetallic Inorganic materials 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- WKMKTIVRRLOHAJ-UHFFFAOYSA-N oxygen(2-);thallium(1+) Chemical class [O-2].[Tl+].[Tl+] WKMKTIVRRLOHAJ-UHFFFAOYSA-N 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 229910052761 rare earth metal Inorganic materials 0.000 description 1
- 150000002910 rare earth metals Chemical class 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N60/00—Superconducting devices
- H10N60/01—Manufacture or treatment
- H10N60/0268—Manufacture or treatment of devices comprising copper oxide
- H10N60/0801—Manufacture or treatment of filaments or composite wires
Landscapes
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Superconductors And Manufacturing Methods Therefor (AREA)
Abstract
A superconductor composite comprises a plurality of metal multifilaments 2 in a superconducting matrix 3. The composite is produced by mixing a precursor with particles of a metal within a metal enclosure, drawing down the enclosure, precursor and metal particles and thermally processing to form a continuous monofilament of superconducting composite including multifilaments of metal. The monofilamentary superconductor may comprise a plurality of silver multifilaments in a ceramic oxide superconducting matrix. The precursor may be Nb3Sn or NbTi, or a ceramic oxide powder e.g. Bi or Tl oxide compounds; the particles and the enclosure may be silver or an alloy thereof. The metal filaments act as a catalyst to accelerate the thermal processing step. <IMAGE>
Description
SUPERCONDUCTING COMPOSITES
This invention relates to superconducting composites and a method of production.
The performance of a superconducting material in the form of a wire, tape or cable is described in relation to its current carrying capacity in a magnetic field below a critical temperature by the j-H characteristic, shown in
Figure 1, curve (a), where j is the current density in
Amperes per sq cm of cross sectional area and H is the externally applied magnetic field in Tesla. In practise, the j-H characteristic of a superconductor is improved by reducing the diameter or the cross-sectional area of the superconducting element or filament when in the form of a wire or tape as illustrated by Figure 1, curve (b).It follows that a high current carrying superconductor carrying of the order of 100 to 1000A current consists of a large number of superconducting filaments within an outer metal sheath with each filament carrying a relatively small current, but at a high current density. At the same time, each filament of superconductor is contained within an individual metal sheath, where the metal may be silver, a silver alloy or another metal or metal alloy or a composite combination of layers in the sheath, to provide additional mechanical strength and protection for the enclosed superconducting filament.
The production of the superconductor usually commences with the filling of a metal tube such as a silver tube with finely divided ceramic oxide precursor powder, and is followed by thermal and mechanical processing during which the metal tube and powder are drawn down to a small diameter and the ceramic oxide precursor is converted to a continuous mono-filamentary form which exhibits superconductivity below a certain critical temperature. To make a multi-filamentary superconductor, a number of metal sheathed monofilaments are combined into a Stage 1 bundle in an outer sheath, which is then drawn down to a smaller diameter together with further thermal processing to make a Stage 1 multi-filamentary structure. The resultant structure comprises superconducting filaments embedded in a composite metal structure hereinafter referred to as a matrix.A number of Stage 1 multi-filamentary structures are then combined into a Stage 2 bundle, which is then drawn down to a smaller diameter together with further thermal processing to make a Stage 2 multi-filamentary structure. By way of example, a Stage 1 multi-filamentary structure may contain 7 monofilaments, while a Stage 2 structure may contain 7 Stage 1 structures, i.e. 49 monofilaments. An example of this is shown in Figure 2.
The superconducting filaments 5 from each stage 1 structure remain in the same area, but the metal matrix 6 of each structure tends to merge with the metal of the outer sheath 7.
A bundle of Stage 3 multi-filamentary structures can be combined to make a Stage 4 structure (with say 343 monofilaments); and so on to Stage 5 with 2401 monofilaments. The final stage of the processing may include rolling operations to convert the multi-filamentary wire (with a circular cross-section) into a tape (with a flat section with a large ratio of width to thickness). If the final product is a cable then this will necessitate incorporation of a number of multi-filamentary wires or tapes into a cable structure via cable-making procedures.
The manufacture of long lengths of multi-filamentary superconductor is therefore an expensive process in which the final product consists of many continuous long lengths of superconducting monofilaments in a metal matrix.
In accordance with the present invention, a method of production of a superconducting composite comprises, mixing a precursor with particles of a metal within a metal enclosure; and drawing down the enclosure, precursor and metal particles such that a continuous monofilament comprising a superconducting matrix including multifilaments of metal is formed.
The present invention provides a method of producing a multifilamentary superconducting composite by a process which is greatly simplified by comparison with conventional methods of producing multifilamentary composites. The method does not involve the complex bundling, drawing and thermal processing of monofilaments, Stage 1 multifilaments, and the successive processing of Stage 2, Stage 3, Stage 4 and Stage 5 multi-filaments required by the conventional method, but rather a single stage of drawing.
Other benefits include improved continuity and the maintenance of a uniform cross-section of the superconductor over long lengths of wire and tape at reduced cost.
Preferably, the metal particles act as a catalyst during processing thereby reducing the thermal processing time required.
Preferably, the thermal processing time is 30 hours or less.
Not only is the method of the present invention a simpler process than conventional methods, but the catalytic effect of the metal particles allows the superconducting composite to be produced with reduced thermal processing time enabling considerable savings on heating costs and a more streamlined production process.
The structure, which is the inverse of conventional multi filamentary superconductors, has improved performance under mechanical strain; and is easily manufactured in long lengths, bypassing the complex construction of conventional multi-filamentary superconductors in a metal matrix while retaining the performance.
The precursor may be a metallic compound or metal alloy such as Nb3Sn or NbTi, but preferably, the precursor is a ceramic oxide powder.
Preferably, the metal particles are silver, although silver alloy or other metals could be used.
Preferably, the metal enclosure comprises silver or silver alloy. Other metals could also be used.
The ratio of metal particles to precursor can be biased in favour of one or other, but preferably the metal particles and the precursor are provided in equal volumes.
Typically, the diameter of the metal particles is in the range 50xl0~6m to 200x10'4n and the diameter of the precursor is lxl06m to 5xl06m, although diameter outside these ranges are not excluded.
Typically, the continuous monofilament is formed into wires, tapes or cables. The monofilament may be formed into a tape by further steps of rolling and thermally processing.
In accordance with a second aspect of the invention, a superconducting composite comprising a plurality of metal multi filaments in a superconducting matrix.
As explained above, this composite structure has several advantages over conventional superconductors.
Further, a performance at least equivalent to that of a conventional multi-filamentary superconductor is achieved using the structure of metal multifilaments in a superconducting matrix which is the inverse of a conventional multi filamentary structure, in a shorter thermal processing time.
Typically, the metal multi filaments comprise silver or silver alloy.
Preferably, the superconducting matrix comprises a ceramic oxide.
An example of a method of producing superconducting composites in accordance with the invention will now be described with reference to the accompanying drawings in which:
Figure 1 is a typical j-H characteristic illustrating superconducting performance;
Figure 2 is a cross-section through a conventional multi filamentary superconductor; and,
Figure 3 is a cross-section through a superconducting composite manufactured according to the method of the present invention.
In the method of the present invention a metal tube is filled with finely divided ceramic oxide precursor powder which is mixed additionally with large particles of metal such as silver, which particles may be spherical. The ratio of volume of metal powder to ceramic oxide powder can vary, typically in the range 30 - 70% by volume of 2 5pm diameter ceramic oxide powder and 70 - 30% by volume of 50 - 200m diameter silver metal powder, but commonly approximately equal volumes are used.
After drawing to a small diameter and thermal processing to make a wire with circular cross-section, the wire is optionally subjected to steps of rolling and further thermal processing to make a tape with a flat cross-section. The resulting superconductor 1 (shown in
Figure 3) consists of a continuous monofilament of ceramic oxide superconductor comprising a superconducting matrix 3 in which are embedded a large number of discontinuous filaments of metal 2, the whole being contained inside a metal sheath 4. During the drawing down process, the metal particles become elongated into long, thin filaments with circular cross-section. If the product is to be in the form of a tape the metal filaments are flattened, during the subsequent rolling process, to have flat cross-sections with width to thickness ratios greater than one. The effect of the metal filaments, of circular or flat crosssect ion, is to break up the superconductor into many continuously linked elements with the necessary crosssection, generally half the total cross-section, to yield an advantageously high j-H characteristic, similar to
Figure 1 (b). At the same time, the metal filaments act as a catalyst so as to accelerate the thermal processing which includes the conversion of the ceramic powder to the superconducting state, and thereby reducing the total thermal processing time from the order of 100 - 200 hours, to the order of 10 - 30 hours.
The invention is applicable to all types of ceramic oxide superconductor, including R123 and variants (R is Y or rare earth) Bismuth and Thallium oxide compounds and variants.
Claims (15)
1. A method of production of a superconducting composite, the method comprising mixing a precursor with particles of a metal within a metal enclosure; and drawing down the enclosure, precursor and metal particles such that a continuous monofilament comprising a superconducting matrix including multifilaments of metal is formed.
2. A method according to claim 1 wherein the metal particles act as a catalyst during processing whereby reduced thermal processing time is required.
3. A method according to claim 1 or claim 2 wherein a thermal processing time of 30 hours or less is required.
4. A method according to any preceding claim wherein the precursor is a ceramic oxide powder.
5. A method according to any preceding claim wherein the metal particles are silver.
6. A method according to any preceding claim wherein the metal enclosure comprise silver or silver alloy.
7. A method according to any preceding claim wherein the metal particles and the precursor are provided in equal volumes.
8. A method according to any preceding claim wherein the metal particles have a diameter in the range 50xl0~6m to 200xl0~6m.
9. A method according to any preceding claim wherein the precursor is in the form of a powder having particles of diameter in the range lxl0~6m to 5xl0~6m.
10. A method according to any preceding claim further comprising the steps of rolling and thermally processing the monofilament to form a tape.
11. A superconducting composite comprising a plurality of metal multifilaments in a superconducting matrix.
12. A superconducting composite according to claim 11 wherein the metal is silver.
13. A superconducting composite according to claim 11 or claim 12 wherein the superconducting matrix comprises a ceramic oxide.
14. A method of production of a superconducting composite as hereinbefore described with reference to Figure 3.
15. A superconducting composite as hereinbefore described with reference to Figure 3.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9520742A GB2294802A (en) | 1994-10-08 | 1995-10-09 | Superconducting composites and method of production |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9420365A GB9420365D0 (en) | 1994-10-08 | 1994-10-08 | Multi-filamentary ceramic oxide superconducting composite wires, tapes and cables |
| GBGB9511481.5A GB9511481D0 (en) | 1995-06-07 | 1995-06-07 | Multi-filamentary ceramic oxide superconducting composite wires,tapes and cables reduced thermal processing time |
| GB9520742A GB2294802A (en) | 1994-10-08 | 1995-10-09 | Superconducting composites and method of production |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB9520742D0 GB9520742D0 (en) | 1995-12-13 |
| GB2294802A true GB2294802A (en) | 1996-05-08 |
Family
ID=27267423
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9520742A Withdrawn GB2294802A (en) | 1994-10-08 | 1995-10-09 | Superconducting composites and method of production |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2294802A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2444090A (en) * | 2006-11-24 | 2008-05-28 | David Peter Lee | Elecrical conductor |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH10172227A (en) * | 1996-12-11 | 1998-06-26 | Victor Co Of Japan Ltd | Write protector and disc cartridge |
-
1995
- 1995-10-09 GB GB9520742A patent/GB2294802A/en not_active Withdrawn
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH10172227A (en) * | 1996-12-11 | 1998-06-26 | Victor Co Of Japan Ltd | Write protector and disc cartridge |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2444090A (en) * | 2006-11-24 | 2008-05-28 | David Peter Lee | Elecrical conductor |
Also Published As
| Publication number | Publication date |
|---|---|
| GB9520742D0 (en) | 1995-12-13 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |