GB2257437A - Method for forming triniobium tin superconductor - Google Patents
Method for forming triniobium tin superconductor Download PDFInfo
- Publication number
- GB2257437A GB2257437A GB9213163A GB9213163A GB2257437A GB 2257437 A GB2257437 A GB 2257437A GB 9213163 A GB9213163 A GB 9213163A GB 9213163 A GB9213163 A GB 9213163A GB 2257437 A GB2257437 A GB 2257437A
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- GB
- United Kingdom
- Prior art keywords
- tin
- tape
- triniobium
- niobium
- copper
- 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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- KNYAMFPIBOJKIO-UHFFFAOYSA-N [Nb].[Nb].[Nb].[Sn] Chemical compound [Nb].[Nb].[Nb].[Sn] KNYAMFPIBOJKIO-UHFFFAOYSA-N 0.000 title claims abstract description 84
- 238000000034 method Methods 0.000 title claims abstract description 23
- 239000002887 superconductor Substances 0.000 title description 12
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 claims abstract description 54
- 229910052758 niobium Inorganic materials 0.000 claims abstract description 49
- 239000010955 niobium Substances 0.000 claims abstract description 49
- 229910052718 tin Inorganic materials 0.000 claims abstract description 41
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 claims abstract description 40
- 239000011248 coating agent Substances 0.000 claims abstract description 33
- 238000000576 coating method Methods 0.000 claims abstract description 33
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims abstract description 29
- 239000010949 copper Substances 0.000 claims abstract description 29
- 229910052802 copper Inorganic materials 0.000 claims abstract description 25
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 12
- 239000001301 oxygen Substances 0.000 claims abstract description 12
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 12
- 229910052726 zirconium Inorganic materials 0.000 claims abstract description 7
- 229910052735 hafnium Inorganic materials 0.000 claims abstract description 4
- 239000000203 mixture Substances 0.000 claims abstract description 3
- 229910052702 rhenium Inorganic materials 0.000 claims abstract description 3
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 claims description 6
- VBJZVLUMGGDVMO-UHFFFAOYSA-N hafnium atom Chemical compound [Hf] VBJZVLUMGGDVMO-UHFFFAOYSA-N 0.000 claims description 3
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims description 2
- 229910052770 Uranium Inorganic materials 0.000 claims description 2
- 229910052750 molybdenum Inorganic materials 0.000 claims description 2
- 239000011733 molybdenum Substances 0.000 claims description 2
- WUAPFZMCVAUBPE-UHFFFAOYSA-N rhenium atom Chemical compound [Re] WUAPFZMCVAUBPE-UHFFFAOYSA-N 0.000 claims description 2
- JFALSRSLKYAFGM-UHFFFAOYSA-N uranium(0) Chemical compound [U] JFALSRSLKYAFGM-UHFFFAOYSA-N 0.000 claims 1
- 238000006243 chemical reaction Methods 0.000 abstract description 20
- 229910000679 solder Inorganic materials 0.000 abstract description 14
- 229910001128 Sn alloy Inorganic materials 0.000 abstract description 9
- 238000000137 annealing Methods 0.000 abstract description 8
- 229910000881 Cu alloy Inorganic materials 0.000 abstract description 4
- 230000015572 biosynthetic process Effects 0.000 abstract description 4
- 229910000978 Pb alloy Inorganic materials 0.000 abstract description 3
- 229910052751 metal Inorganic materials 0.000 description 13
- 239000002184 metal Substances 0.000 description 13
- 230000005291 magnetic effect Effects 0.000 description 8
- 239000000523 sample Substances 0.000 description 8
- 239000000463 material Substances 0.000 description 7
- KUNSUQLRTQLHQQ-UHFFFAOYSA-N copper tin Chemical class [Cu].[Sn] KUNSUQLRTQLHQQ-UHFFFAOYSA-N 0.000 description 6
- 230000035484 reaction time Effects 0.000 description 6
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- 229910000657 niobium-tin Inorganic materials 0.000 description 4
- 239000012298 atmosphere Substances 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- 230000003647 oxidation Effects 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- 229910001281 superconducting alloy Inorganic materials 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- 230000001464 adherent effect Effects 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 238000005275 alloying Methods 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 238000002048 anodisation reaction Methods 0.000 description 2
- 239000012300 argon atmosphere Substances 0.000 description 2
- 230000006835 compression Effects 0.000 description 2
- 238000007906 compression Methods 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- -1 i.e. Substances 0.000 description 2
- 229910000765 intermetallic Inorganic materials 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 229910000484 niobium oxide Inorganic materials 0.000 description 2
- ZKATWMILCYLAPD-UHFFFAOYSA-N niobium pentoxide Chemical compound O=[Nb](=O)O[Nb](=O)=O ZKATWMILCYLAPD-UHFFFAOYSA-N 0.000 description 2
- KJSMVPYGGLPWOE-UHFFFAOYSA-N niobium tin Chemical compound [Nb].[Sn] KJSMVPYGGLPWOE-UHFFFAOYSA-N 0.000 description 2
- URLJKFSTXLNXLG-UHFFFAOYSA-N niobium(5+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Nb+5].[Nb+5] URLJKFSTXLNXLG-UHFFFAOYSA-N 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 238000005476 soldering Methods 0.000 description 2
- 229910052720 vanadium Inorganic materials 0.000 description 2
- GPPXJZIENCGNKB-UHFFFAOYSA-N vanadium Chemical compound [V]#[V] GPPXJZIENCGNKB-UHFFFAOYSA-N 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- GYHNNYVSQQEPJS-UHFFFAOYSA-N Gallium Chemical compound [Ga] GYHNNYVSQQEPJS-UHFFFAOYSA-N 0.000 description 1
- 229910001257 Nb alloy Inorganic materials 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 238000007792 addition Methods 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000001311 chemical methods and process Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 229910052733 gallium Inorganic materials 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- LQBJWKCYZGMFEV-UHFFFAOYSA-N lead tin Chemical compound [Sn].[Pb] LQBJWKCYZGMFEV-UHFFFAOYSA-N 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 229910052755 nonmetal Inorganic materials 0.000 description 1
- 238000007747 plating Methods 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 229910052938 sodium sulfate Inorganic materials 0.000 description 1
- 235000011152 sodium sulphate Nutrition 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 229910052715 tantalum Inorganic materials 0.000 description 1
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 description 1
- 229910052713 technetium Inorganic materials 0.000 description 1
- GKLVYJBZJHMRIY-UHFFFAOYSA-N technetium atom Chemical compound [Tc] GKLVYJBZJHMRIY-UHFFFAOYSA-N 0.000 description 1
- 229910000597 tin-copper alloy Inorganic materials 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- DNYWZCXLKNTFFI-UHFFFAOYSA-N uranium Chemical compound [U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U][U] DNYWZCXLKNTFFI-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
- C23C2/08—Tin or alloys based thereon
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/26—After-treatment
- C23C2/261—After-treatment in a gas atmosphere, e.g. inert or reducing atmosphere
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/26—After-treatment
- C23C2/28—Thermal after-treatment, e.g. treatment in oil bath
-
- 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
- H10N60/0184—Manufacture or treatment of devices comprising intermetallic compounds of type A-15, e.g. Nb3Sn
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Thermal Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Physics & Mathematics (AREA)
- Manufacturing & Machinery (AREA)
- Superconductors And Manufacturing Methods Therefor (AREA)
- Superconductor Devices And Manufacturing Methods Thereof (AREA)
- Electroplating Methods And Accessories (AREA)
Abstract
A method of forming superconducting triniobium tin tapes by coating a niobium tape in a tin bath and reaction annealing the coated tape to form triniobium tin is improved by coating the niobium tape in a tin bath comprised of about 5 to 25 weight percent copper, about 5 to 25 weight percent lead, and the balance substantially tin. The niobium tape may comprise up to about 5 atomic percent of a solute selected from Zr, Hf, Mo, U, Re or mixtures thereof and up to about 10 atomic percent oxygen. The load, copper, and tin alloy coating promotes rapid formation of a fine grained triniobium tin during reaction annealing of the coated tape. The fine grain size in the triniobium tin provides improved current-carrying capacity in the superconducting tape. The lead, copper, and tin alloy coating that remains on the triniobium tin after reaction annealing also improves the solder bonding of a non-superconducting of copper outer laminae to the triniobium tin. As illustrated in Fig. 3 excess coating of tin alloy 4' covers the triniobium tin on the remaining tape 2'. <IMAGE>
Description
METHOD FOR FORMING: TRINTOBTUM TIN
SEMICONDUCTOR
Background of the Invention
This invention relates to a method of forming a triniobium.tin superconductor having improved currentcarrying capacity, and improved triniobium tin tape.
Superconductivity is that characteristic of certain materials which permits them to conduct electric currents without resistance. A superconducting material exhibits this characteristic only when its temperature is below the superconducting critical temperature of the material, and then only if it is not subject either to a magnetic field greater than the superconducting critical magnetic field of the material or to an electric current greater than the superconducting critical current of the material.
Accordingly, superconductivity can be quenched, i.e., returned to a resistive state, by increasing the temperature, magnetic field, or current to which the superconducting element is subjected above the critical temperature, magnetic field, or current. Quenching of the superconductivity may occur abruptly or more gradually depending upon the particular material, i.e., the relative breadth of its superconducting transition state in terms of temperature, magnetic field, or current.
It is known that selected parent-metals, either pure or preferably containing minor alloying additions, are capable of being reacted with other metals and forming superconducting compounds or alloys that have a high currentcarrying capacity. Parent-metals niobium, tantalum, technetium, and vanadium can be reacted or alloyed with reactive-metals tin, aluminum, silicon, and gallium to form superconducting alloys, such as triniobium tin. As used herein, the term "triniobium tin" is a superconducting alloy in the form of an intermetallic compound comprised of about three niobium atoms per tin atom. Triniobium tin is the superconductor of interest in this invention.
Additionally, it is known that triniobium tin can be improved by first alloying the parent-metal, i.e., niobium with a minor amount of a solute metal having an atom diameter of at least 0.29 angstrom larger than the diameter of the parent-metal atom. U.S. Patent 3,429,032 incorporated by reference herein, discloses improved critical currents in triniobium tin formed by heating niobium comprised of up to about 25 percent zirconium in the presence of excess tin, and a non-metal selected from the group consisting of oxygen, nitrogen, and carbon. It is also known that the reactivemetal tin can be alloyed with copper to improve triniobium tin. In, "Enhancement of the Critical Current Density in
Niobium-Tin" J.S.Caslaw, Cryogenics, February 1971, pp. 5759, incorporated by reference herein, the critical current density of triniobium tin was improved by reacting niobium with a reactive-metat comprised of up to about 45 weight percent copper and the balance tin.
The triniobium tin alloy has been fabricated in various forms, particularly wires and tapes, in efforts to produce devices such as high field superconducting electromagnets. One method for obtaining superconducting tape in a continuous fashion is that wherein a niobium or niobium alloy tape is continuously led through a bath of molten reactive-metal such as tin or tin alloy. The tape picks up a thin coating of the reactive-metal from the molten bath and the tape is subsequently heated in a reaction furnace to cause formation of a superconductive alloy on the surface of the parent-metal tape.
The superconducting alloy formed on the tape is fragile, and outer laminae of non-superconductive metal are applied to the tape to make a laminated superconductor that is strong and capable of being wound onto coils without damage to the superconductive material. For example, a relatively thin tape of niobium foil is treated with tin to form an adherent layer of triniobium tin on the surfaces of the tape, and copper tapes of substantially the same width are soft soldered to each of the major surfaces of the superconductive tape to form a symmetrically laminated structure. Because of the difference in the coefficient of thermal expansion of copper and the niobium-triniobium tin tape, the brittle intermetallic compound is placed in compression even at room temperature, minimizing the danger of mechanical fracture when coiling.
The copper outer laminae serve several other important functions on the tape. When the current load on a superconducting tape exceeds the critical current density,
Jc, the tape is driven into the normal resistive state and a large amount of heat is generated which must be rapidly dissipated or the tape will be damaged. The copper outer laminae provide an alternate normal current path if the triniobium tin becomes non-superconducting, and reduces the heat generated. The copper outer laminae also provide a thermal cooling path for lowering the triniobium tin below the critical temperature of the superconductor. In order for the copper outer laminae to provide such benefits to the superconducting tape, a strong and uniform bond between the triniobium tin and the copper outer laminae is required.
An object of this invention is to provide a method for forming triniobium tin superconductors having improved current-carrying capacity.
Another object of the method of this invention is to provide an improved solder bond between the nonsuperconducting outer laminae and triniobium tin inner layer of a laminated triniobium tin tape.
Brief Description of the Invention
Triniobium tin superconductors having improved current-carrying capacity are formed by the method of this invention. Superconducting triniobium tin tapes are formed by coating a niobium tape in a tin bath, and reaction annealing the coated tape to form triniobium tin. In the method of this invention the niobium tape is coated in a tin bath comprised of about 5 to 25 weight percent copper, about 5 to 25 weight percent lead, and the balance substantially tin. The lead, copper, and tin alloy coating promotes rapid formation of a fine grained triniobium tin during reaction annealing of the coated tape. The fine grain size in the triniobium tin provides improved current-carrying capacity in the superconducting tape.The lead, copper, and tin alloy coating that remains on the triniobium tin after reaction annealing also improves the solder bonding of a nonsuperconducting outer laminae to the triniobium tin.
Brief nescription of the Drawr ngs Fig. 1 is a side view of a niobium tape.
Fig. 2 is a side view of a niobium tape coated with a tin alloy.
Fig. 3 is a side view of a reaction annealed triniobium tin tape.
Fig. A is a side view. of a reaction annealed triniobium tin tape with non-superconducting outer laminae.
Fig. 5 is a cross section view of an apparatus for forming a laminated triniobium tin tape.
FIG. 6 is a graph comparing the current density versus reaction time for triniobium tin superconductors formed from niobium tapes coated with a copper-tin alloy, and niobium tapes coated with a lead-copper-tin alloy.
FIG. 7 is a graph comparing the current density versus grain size for triniobium tin superconductors formed from niobium tapes coated with a copper-tin alloy, and niobium tapes coated with a lead-copper-tin alloy.
Detailed nescrintion of the Invention
Triniobium tin tapes are well known in the art being described, for example, in "Superconducting Properties of Diffusion Processed Niobium-Tin Tape," M. Benz, I.E.E.E.
Transactions of Magnetics, Vol. ItAG-2, No. 4, Dec. 1966, pp 7607764, incorporated by reference herein.
A method of forming continuous lengths of triniobium tin tapes is known, for example, being described in British patents 1,342,726 and 1,254,542, incorporated herein by reference. The method is briefly described by making reference to Figs. 1-4. A niobium tape 2 comprised of up to about 5 atomic percent of a metal selected from the group consisting of zirconium, aluminum, hafnium, titanium, and vanadium, and up to about 5000 parts per million oxygen is contacted with a molten tin bath comprised of up to about 45 weight percent copper to form a coating 4. Alternatively, the tin and copper may be deposited separately onto the niobium wire or tape at least partly by plating. Still further, the tin and copper may be applied to the niobium wire or tape by electrolytic or chemical processes.
The coated niobium tape 10 is reaction annealed at about 850 to 1100-C to react the niobium substrate with the coating and form laminae of triniobium tin 6 on niobium tape 2. Excess coating 4', as shown in Fig 3, covers the triniobium tin 6. The remaining niobium tape 2' is reduced in thickness from reaction with the coating to form the trioniobium tin 6. Non-superconducting outer laminae 8 can be bonded to the reacted tape, for example by soldering, to form a laminated triniobium tin tape 14 having improved strength and formability. For example, solder is applied to the outer laminae 8 and triniobium tin tape 12 and the outer laminae 8 and triniobium tin tape 12 are brought into contact while heated to a suitable soldering temperature to form the laminated triniobium tin tape 14.
The method of this invention is shown by again making reference to FIGS. 1-4. We have discovered that when the niobium tape 2 is coated in a tin bath comprised of about 8 to 10 weight percent lead, about 8 to 10 weight percent copper, and the balance substantially tin to form coating 4, the coated tape can be reactively annealed to form laminae of triniobium tin 6 having improved current-carrying capacity.
Preferably, the lead-copper-tin alloy coating 4 on the niobium tape 2 is uniform and continuous, and about 0.01 to 0.03 grams per square centimeter. In addition, the residual or excess coating 4' of the lead-copper-tin alloy remaining on the triniobium tin after reaction annealing provides an improved solder bond when triniobium tin tape 12 is soldered to outer laminae 8 to form laminated triniobium tin tape 14.
The niobium tape 2 may be comprised of up to about 5 atomic percent of a solute from the group consisting of hafnium, zirconium, molybdenum, uranium, rhenium, or mixtures thereof, up to about 10 atomic percent oxygen, and the balance substantially niobium. Preferably, the niobium tape is comprised of about 1 to 2 atomic percent solute, and about 2 to 4 atomic percent oxygen. Oxidation of the niobium tape surface and internal oxidation of the niobium tape can be preformed by conventional means known in the art, for example, as described in British patent 1,342,726.
Anodization followed by annealing in an inert atmosphere is a preferred means for introducing the oxygen into the niobium tape. A suitable niobium tape 2 is about 10 to 50 microns thick and about 0.076 to 5 centimeters in width.
In a suitable anodization process, a conductor, i.e. the niobium tape is connected as an anode in a suitable electrolytic bath. The electrolytic oxidation results in the formation of a niobium oxide, Nb2O5, film on the surface of the tape. The tape carrying the oxide film is heated in an inert atmosphere, such as argon, to cause the oxygen to diffuse into the tape. The desired concentration of oxygen, for example up to about 10 atomic percent, is diffused into the body of the tape leaving an oxide free tape surface. It is believed the oxygen combines with the solute-elements in the tape.
The niobium tape 2 can be coated by passing the tape through a molten tin bath comprised of the lead-coppertin alloy. Preferably, the coating 4 is chick enough to react with up to about 90 percent of the niobium tape, and leave a residual or excess coating 4' on the triniobium tin 6. The coated tape 10 is heat treated in an inert atmosphere for a time sufficient to form the triniobium tin superconductor 6, for example about 20 to 300 seconds.
Preferably, the reaction anneal is stopped before the niobium tape is fully reacted so that a niobium core 2' remains in the tape to support the brittle triniobium tin 6, and the residual coating 4' covers the triniobium tin 6.
The reacted tape 12 is soldered between nonsuperconducting outer laminae 8 of metal which have a greater coefficient of thermal expansion than the triniobium tin, preferably copper. The outer laminae 8 are about the same width as tape 12, and about 75 to 150 microns thick. Solder bonding can be performed as shown for example in FIG. 5.
Triniobium tin tape 12 and outer laminae 8 are led into a solder bath 20, heated to about 230 to 250 C. Alignment rollers symmetrically align and contact tape 12 with outer laminae 8 in the bath 20. Roller-wipers 22 remove excess solder while providing intimate contact under pressure to form the solder bond between tape 12 and outer laminae 8 to form laminated triniobium tin tape 14.
Referring back to FIGS. 3-4, preferably, a conventional lead-tin solder comprised of about 37 weight percent lead and the balance tin is used to bond the outer laminae 8 to the triniobium tin tape 12. The residual layer 4' of the lead-copper-tin coating provides an improved solder bonding between the triniobium tin tape 12 and outer laminae 8. The ease of forming the solder bond, and the uniformity and strength of the solder bond are improved by the residual coating 4' comprised of the lead-copper-tin alloy. For example, the solder bond can be formed at a lower temperature or in a shorter period of time with the residual coating 4' comprised of the lead-copper-tin alloy as compared to a residual coating 4' of tin or copper-tin alloy.As a result, the outer-laminae 8 are maintained at a higher strength so that triniobium tin 6 is maintained at a higher level of compression, and laminated triniobium tin tape 14 has greater formability.
Additional features and advantages of the method of this invention are shown in the following examples. Currentdensity of the triniobium tin tapes formed in the following
Examples was measured by the conventional four probe resistance measurement technique well known in the art.
Briefly described, two voltage probes were soldered onto the superconducting tape a short distance apart. Current leads were soldered onto the superconducting tape at a further distance from each of the voltage probes. The triniobium tin tapes were cooled to 4.2 K by cooling in liquid nitrogen, followed by cooling in liquid helium. A magnet having a magnetic field of about 5 Tesla was aligned over the tapes so that the magnetic field was perpendicular to the current path in the superconducting tape. A current was passed through the tapes in increasing steps, and the voltage was recorded from the probes on the tapes. In this test, the critical current was defined as the current which caused a voltage differential of 0.2 microvolts between the probes.
Example 1
A niobium tape about 25 millimeters in width, 25 microns thick, and comprised of about 1.0 weight percent zirconium was obtained Teledyne Wah Chang, Albany, Oregon.
The niobium tape was anodized by passing the tape through an aqueous bath heated to about 90 C, and comprised of about 7 grams per liter of sodium sulfate. A potential of 145 volts was applied between the tape as the anode, and a stainless steel cathode. The tape was anodized in the bath at a rate of about 10 feet per minute. The anodized tape was passed at a rate of about 2 feet per minute through a tube furnace having a heating zone about 3 feet long, and heated to 1000-C in an argon atmosphere. The niobium oxide on the tape surface was decomposed to form substantially oxide-free tape surfaces of metallic niobium, and the oxygen diffused into the body of the tape.
Samples of the internally oxidized tape were contacted with a tin bath comprised of about 16.6 weight percent copper and the balance substantially tin. The tin bath was heated to about 1050-C, and the tape was passed through the bath at a rate of about 10 feet per minute to produce an adherent continuous film of about 0.03 grams per square centimeter of the tin-copper alloy on the tape surface. The tin coated tape was heat treated for various reaction times from 25 to 600 seconds in an argon atmosphere tube furnace at temperatures ranging from 1000 to 1150-C.
The reacted tape had a triniobium tin reaction layer of about 2.6 to 10.8 microns on each side of the tape, and about 1 to 22 microns of unreacted niobium at the core of the tape. The reaction temperature, reaction time, thickness of triniobium tin, and measured properties of critical current, and current density for each tape sample are shown below in Table I.
Table I.
Triniobium Tin Tape From Niobium Tape Coated in Tin Bath
Comprised of 16.6 Weight Percent Copper
Sample Reaction Reaction Nb3Sn Jc at 5
No. Temp Time Thickness Tesla ( C) (Sec.) (Microns) (A/cm2)
1 1000 150 2.6 7.01
2 1000 300 4.3 10.3
3 1000 500 9.7 8.76
4 1000 600 9.7 8.76
5 1050 180 6.1 8.04
6 1150 25 2.6 6.25
7 1150 50 4.1 9.15
8 1150 75 8.1 6.74
9 1150 100 10.8 7.41 Example2 Samples of triniobium tin superconducting tape were formed by the method in Example 1, except the tin bath was comprised of about 8.8 weight percent copper, 8.8 weight percent lead, and the balance substantially tin. The reaction temperature, time, thickness of triniobium tin, and resulting measured properties are shown below in Table II.
Tabletl Triniobium Tin Tape From Niobium Tape Coated in Tin Bath
Comprised of 8.8 Weight Percent Copper, 8.8 Weight Percent
Lead, Balance Substantially Tin.
Sample Reaction Reaction Nb3Sn Jc at 5
No. Temp Time Thickness Tesla ( C) (Sec.) (Microns) (A/cm2)
10 1050 150 3.3 11.47
11 1050 200 5.1 10.77
12 1050 250 6.8 11.84
By comparing the data in Tables I and II it can be seen that the triniobium tin formed from the lead-copper-tin alloy coating has an improved current density as compared to the triniobium tin formed from the copper-tin coating. The improved current-carrying capacity in triniobium tin tape formed by the method of this invention is further shown by making reference to FIGS. 6 and 7. FIGS. 6 and 7 are graphs comparing the current density versus reaction time for triniobium tin tapes formed by reacting niobium tapes coated with copper-tin alloy, and niobium tapes coated with leadcopper-tin alloy.
The current density of about 100 samples of triniobium tin tape formed by the method in Example 1 were averaged to produce the plot shown by the open circles in
FIGS. 6 and 7. It can be seen that as reaction time increases for niobium reacted with copper-tin alloy coating, the current density of the triniobium tin decreases due to the growth of the grains in the triniobium tin layer.
However, the triniobium tin superconductor formed by reacting niobium with the lead-copper-tin alloy coating maintains a finer grain size as reaction time increases, and current density is improved over the prior art triniobium tin superconductor.
Claims (6)
1. A method for improving the current-carrying capacity of triniobium tin superconducting tape formed by coating a niobium tape in a tin bath, and reacting the coated tape to form triniobium tin, comprising
coating the niobium tape in a tin bath comprised of about 5 to 25 weight percent lead, about 5 to 25 weight percent copper, and the balance substantially tin.
2. The method of claim 1 wherein the niobium tape is comprised of about 1 to 2 atomic percent zirconium, and about 2 to 4 atomic percent oxygen.
3. A method of forming a laminated triniobium tin tape according to claim 1 wherein the triniobium tin tape has an excess layer of the tin bath coating and is soldered ta a copper outer laminae.
4. A method for improving the current-carrying capacity of triniobium tin superconducting tape formed from a niobium tape comprised of up to about 5 atomic percent of a solute from the group consisting of zirconium, hafnium, molybdenum, uranium, rhenium, or mixtures thereof and up to about 10 atomic percent oxygen, coating the tape in a tin bath, and reacting the coated tape to form triniobium tin, the improvement comprising:
coating the niobium tape in a tin bath comprised of about 5 to 25 weight percent lead, about 5 to 25 weight percent copper, and the balance substantially tin.
5. A method of forming a laminated triniobium tin tape according to claim 4 wherein the triniobium tin tape has an excess layer of the tin bath coating and is soldered to a copper outer laminae.
6. A method according to Claim 1 substantially as described herein.
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
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US72301791A | 1991-06-28 | 1991-06-28 |
Publications (3)
Publication Number | Publication Date |
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GB9213163D0 GB9213163D0 (en) | 1992-08-05 |
GB2257437A true GB2257437A (en) | 1993-01-13 |
GB2257437B GB2257437B (en) | 1994-05-18 |
Family
ID=24904459
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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GB9213163A Expired - Lifetime GB2257437B (en) | 1991-06-28 | 1992-06-22 | Method for forming triniobium tin semiconductor |
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JP (1) | JPH0799652B2 (en) |
GB (1) | GB2257437B (en) |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0690143A1 (en) * | 1994-06-27 | 1996-01-03 | General Electric Company | Method of coating niobium foil |
US5505790A (en) * | 1994-09-09 | 1996-04-09 | General Electric Company | Method for enhancing critical current of triniobium tin |
US5540787A (en) * | 1995-06-14 | 1996-07-30 | General Electric Company | Method of forming triniobium tin superconductor |
GB2308490A (en) * | 1995-12-18 | 1997-06-25 | Oxford Instr Ltd | Superconductor and energy storage device |
US6358331B1 (en) * | 1995-04-03 | 2002-03-19 | General Electric Company | Method for improving quality of triniobium tin superconductor in manufacturing environment by controlling iron content in molten tin bath |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN110560817A (en) * | 2019-08-26 | 2019-12-13 | 苏州新材料研究所有限公司 | continuous soldering device for superconducting materials |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB1342726A (en) * | 1970-02-04 | 1974-01-03 | Plessey Co Ltd | Electrical conductors |
US4323402A (en) * | 1979-02-09 | 1982-04-06 | National Research Institute For Metals | Method for producing superconducting Nb3 Sn wires |
-
1992
- 1992-06-22 GB GB9213163A patent/GB2257437B/en not_active Expired - Lifetime
- 1992-06-25 JP JP4166513A patent/JPH0799652B2/en not_active Expired - Lifetime
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB1342726A (en) * | 1970-02-04 | 1974-01-03 | Plessey Co Ltd | Electrical conductors |
US4323402A (en) * | 1979-02-09 | 1982-04-06 | National Research Institute For Metals | Method for producing superconducting Nb3 Sn wires |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0690143A1 (en) * | 1994-06-27 | 1996-01-03 | General Electric Company | Method of coating niobium foil |
US5505790A (en) * | 1994-09-09 | 1996-04-09 | General Electric Company | Method for enhancing critical current of triniobium tin |
US6358331B1 (en) * | 1995-04-03 | 2002-03-19 | General Electric Company | Method for improving quality of triniobium tin superconductor in manufacturing environment by controlling iron content in molten tin bath |
US5540787A (en) * | 1995-06-14 | 1996-07-30 | General Electric Company | Method of forming triniobium tin superconductor |
GB2308490A (en) * | 1995-12-18 | 1997-06-25 | Oxford Instr Ltd | Superconductor and energy storage device |
Also Published As
Publication number | Publication date |
---|---|
JPH05198227A (en) | 1993-08-06 |
GB9213163D0 (en) | 1992-08-05 |
GB2257437B (en) | 1994-05-18 |
JPH0799652B2 (en) | 1995-10-25 |
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