DE2355008C3 - Method and device for producing a superconductor with a layer of the A15 phase of the Nb-Al or Nb-Al-Ge system - Google Patents

Description

The invention relates to a method of manufacturing a superconductor with a layer of the A15 phase of the system Nb-Al and Nb-Al-Ge, wherein a Niobträger in a to a temperature of 800 ⁰ C and more heated aluminum or aluminum -germanium-melt introduced and then a Glühbehandiung is subjected at a temperature above 800 ⁰ C in an inert atmosphere.

The A15 phases of the Nb-Al and Nb-Al-Ge systems already become superconducting at relatively high temperatures and only lose this state in very high magnetic fields. In the Nb-Al system, the A15 phase has the composition Nb ₃ Al or a composition that differs only slightly from this. Maximum critical temperatures T ₀ of 18.8 K and upper critical magnetic fields B _n of approximately 30 Tesla at 4.2 K were specified for Nb _{3 Al.} For the A15 phase of the Nb-Al-Ge system with a niobium content of around 75 atomic percent, maximum critical temperatures T _e of 20.7 K _{were found in the composition range of approximately Nb 3} (Al ₁ -IGe ₁ ) with 0 < χ <0.25 and upper critical magnetic fields B _cz of about 40 Tesla at 4.2 K are reported (cf. Zeitschrift für Naturforschung 25 a [1970], pp. 1659 to 1669). These properties of the A15 phases of the Nb-Al and Nb-Al-Ge systems are not exceeded by any other known superconductor. The A15 phases mentioned are therefore of great technical interest, for example for use in superconducting magnet coils.

However, the technical application of these materials has so far failed due to various obstacles. On the one hand, the critical current densities achieved so far are relatively low. For example, molten or powder metallurgically prepared samples of said A15-phases have only critical current densities j _e of about 10 ³ Acm ~ ² in a magnetic field of 5 Tesla and at a temperature of 4.2 K ^0. Only three procedures have so far been able to

“De layers with technically interesting values, critical current densities of 10 * Acm- ² and more. These are two ways of producing superconductors with layers

subjected to an annealing treatment at a temperature between 800 and 1000 ° C. in an inert atmosphere shall be.

_X1U ., _N. . ,,. ,, The object of the invention is to

From Nb-Al-Ge and around em method 5 of the type mentioned above, as far as possible - a superconductor with a layer simple production of superconductors only one, .__. by Nb-Al. In the case of the first two layers of the A15 phase of the Nb-Al system or the tett process, an Nb-A.-Ge layer Nb-Al-Ge will be made possible, while at the same time raög- J, cathode sputtering or condensation borrowed high critical temperatures and for technical ion applied to a carrier in a high vacuum io applications useful critical current densities er i j. Vac. May be. TechnoL, 7 [1970] p. 127 ff., And should be aimed. In particular, the conti- _L ppL Phys., 43 [1972], p. 2407 ff). In the last case (Metallurgical Transactions, 3
a pp. 1177 to 1181) is used to produce a
aleiters with an Nb ^ Al layer an aluminized, 15
Niobium with aluminum diffusion seams

In particular, the continuous production of long wires or strips should also be used thin layers of the A15 phases mentioned may be possible.

According to the invention, this object is achieved by introducing the niobium carrier into an aluminum melt, which is ^{heated to 800 to 140O 0} C and is saturated with niobium or niobium and germanium, with an aluminum melt consisting of NbAl ₃ and Al or Nb (Al ₁ Ge) ₃ .

. annealed at a temperature above 1870 ⁰ C for 8 to iiden long. The aluminum was ut the niobium foil by melting a

Aluminum wire is provided over the foil or by adding a 0.5 to 5 μm thick layer and evaporate or by electrolytic deposition from closing annealing treatment of the so coated an aluminum salt carrier with a temperature of about 300 to 500 ° C at a temperature of 1700 to 1960 ° C melt applied. It takes 0.5 to 5 seconds for the aluminum to form. The coated film was then applied to the diffusion seam

heated to a temperature between 800 and 900 ^{c C.} a ₅ essentially consists of two steps, namely first of all, although the above-mentioned processes remove A15 layers with the production of a niobium and aluminum or niobium, relatively high critical current densities containing aluminum and germanium, they appear to be technically useful for production the surface of the niobium-containing aluminum or aluminum which has not yet been heated to 1400 ° C in the 800 to bar superconductors with such layers. On the one hand, each of these processes requires a 3 ° minium-germanium melt, which is not very expensive in terms of equipment; Al-Ge were made by annealing only short wire samples, layered niobium carriers at a temperature of 1700 to 1960 "C for the production of long superconducting wires 35 se of the system Nb-Al approximately the composition winding of superconducting coils is required sinH. Nb ₃ Al possesses and which for high critical tempera-Another difficulty, that of a technical door favorable range of the A15-phase of the system application of the mentioned A15-phases So far, Nb-Al-Ge has been opposed to the compositions Nb ₃ (Al ₁ -J-Ge ₁ ), consists in the fact that these phases comprise very much with 0 <χ < 0.25, the Gesa extends mtbröde and only to a small extent elastically deformable 40 area in which the method according to the invention applies. In the case of technically usable superconductors it should be possible to apply, practically to A15 phases, the composition therefore the A15 layers are only a few μm thick and settlements Nb ₃ (AIi-SGe *) with 0 < χ < 0.25. should be as close as possible to the neutral fiber of the conductor. For the first step, it is special

lie. In the above-mentioned, elaborate essential that the aluminum melt was allowed to run with niobium, the production of long conductors is saturated with 45 or niobium and germanium. If you have considerable difficulties with thin layers, put a niobium carrier in an appropriate temperature range. For the production of superconductors with layers for heated aluminum melt, the A15 phases of other systems, in particular with the support surface, form a non-uniform ge-layer made of Nb ₃ Sn and V ₃ Ga Crystallites that are known together, which meet these requirements, for example contain NbAl ₃ . If the carrier is then _{removed from the melt by the deposition of Nb 3} Sn on a gel, aluminum also adheres to the suitable carrier formed from the gas phase or the one-NbAl ₃ , so that the formed diffusion of tin or gallium in the niobium or layer consists entirely of NbAl ₃ and Al. If vanadium wires were made of copper-tin or copper, this coating would be wrapped in a pure aluminum-gallium jacket that surrounds these wires. However, up to now, both processes have not been able to accumulate niobium in the melt, since part of the NbAl ₃ formed in a satisfactory manner for the production of supra-formed NbAl 3 does not remain fixed on the carrier, but instead conducts with Nb ₃ Al or Nb ₃ (Al, Ge) layers anpe- is absorbed by the melt. Because of this be turned. Change in the composition of the weld pool

^Finally , a uniform coating, which is no longer described in FR-OS 21 36 868, is unsuitable, primarily to ensure, as experiments in the production of a superconductor with an Nb ₃ Sn layer have shown , already proven in the coating of a specific process, in which to produce 80 m long niobium points of a superconductor running through the melt with a layer of the A 15 phase wire, the thickness of the layer formed along the line of the Nb-Al system or Nb-Al-Ge change a niobium carrier ⁶ S wire very strongly. At a temperature of initially in a temperature of 850 to a melt of 1400 ° C, for example, 95O ⁰ C heated aluminum or aluminum ger- introduced on such an 80 m long niobium wire with 0.2 mm manium melt and subsequently an increase in the mean effective diameter

Aluminum layer thickness from initially 1.2 to 8.4 μm. in the first process step on the niobium carrier - the niobium content of the melt, the volume of which is applied completely to the layer. The resulting 3 ml, increased during the passage of the wire, the melt film then picks up niobium from the substrate. to 2 atomic percent. Under »medium effective, the A 15 phase is then formed, if necessary, aluminum layer thickness« is the calculated 5 in addition to other intermetallic phases of the weakening of a layer made of pure aluminum promising systems. Stand in the temperature range that corresponds to the aluminum content of the A15 phase ^{actually grown between 1850 and 1960 0} _{C layer of NbAl 3} and Al. by crystallization of the melt film, in the tempera-When coating from an aluminum-germanium furbereich between 1700 and 185O ⁰ C by solid melt changes, as tests have shown, io reaction, for example between niobium and the not only the content of the melt of niobium, but the next σ phase of the composition also the ratio of germanium to aluminum Nb ₂ Al. At temperatures above 1960 ° C none could be in the melt, since the Nb ₃ Al layer is formed on the niobium carrier, since the temperature-increasing layer has a different ratio of aluminum to the peritectic decomposition of this layer than that Melt. The 15 is 1960 ° C. At temperatures below sequence is here again a very uneven 1700 ⁰ C even with relatively long Reakmäßige coating. tion times insufficient layer thickness of the

If, on the other hand, the aluminum melt reaches the corresponding A 15 phase. Furthermore, at temperatures corresponding to the method according to the invention, superconducting layers formed with niobium below 1700 ° C. or niobium and germanium are saturated, the relatively low critical temperatures remain. The composition of the melt during the annealing times of 0.5 to 5 seconds are constant over the stratification. In the course of the coating, the above-mentioned layer thicknesses of the A 15 phase of approximately 1 to 10 μm matched _{only sediments made of NbAl 3 in the melt.} In the case of shorter annealing times, Nb (Al ₅ Ge) ₃ and Ge are respectively, while the composition of the achievable layer thicknesses is usually too small, and the liquid phase remains unchanged. In the case of longer annealing times, the constant composition of the liquid amount aluminum diffuses from the formed sigen phase, in addition to the constant temperature, is the Nb ₃ Al layer in the niobium carrier material. Similar to the melt, the prerequisite that conditions such as those explained for the formation of the A 15 phase, longer niobium carriers with layers of constant Nb-Al system, can be provided within the framework of strength. The amounts of formation of the A 15 phase of the Nb-Al-Ge system required for the saturation of the reaction conditions mentioned also for the aluminum melt. Niobium or niobium and germanium are of course dependent on particularly high critical temperatures and the respective temperature of the melt. For example, the amount of niobium required to saturate an aluminum superconductor with a layer of the A 15 phase of the minium melt is achieved with a 35 Nb-Al system if the niobium carrier temperature of 800 ° C is about 2 atomic percent, at _{a layer consisting of NbAl 3} and Al at 1400 ° C about 12 atomic percent is provided by introducing into the aluminum temperature of 1000 ° C saturated with niobium and about 4 atomic percent in the case of minium melt, the aluminum-niobium of which. content of a medium effective aluminum layer

In the process according to the invention to 4 ° thick corresponds to 1 to 2 μιη, and the so-coated turning temperature range for the melt of niobium in an inert atmosphere 1 to 3 seconds 800 to 1400 ° C ensures that the formation of the long at a Temperature of 1700 to 1900 ° C desired layers of NbAl ₃ and Al or annealing. It is even more favorable here to carry out the be-Nb (Al, Ge) ₃ with a thickness of 0.5 to 5 μm rapidly layered niobium carrier at a temperature of 1870 enough to anneal a coating of the niobium carrier from 45 to 1900 ° C, because in this temperature range, the A15 layer crystallizes from the melt and can be moved in a technically rational run. Has particularly favorable critical values depending on the particular. At the temperature of the layer thickness and the respective temperature of the ratures above 1900 ⁰ C, the already er-melt already begins, the required reaction times, imagined diffusion of aluminum into the niobium, are between 0.1 and 4 seconds. At temperatures 50 more sluggish, the lower critical values of the remaining melt below 800 ^° C. would result in the layer A15 layer

Especially over 1400 ⁰ C already barely con- average effective aluminum layer thickness of 1 run education for technical applications too slowly at low temperatures in order to achieve the aforementioned trollierbar quickly. From the loading to 2 μm, it is when the niobium carrier for coating is coated layers with a layer thickness 55 for 0.1 to 0.5 seconds into the 0.5 to 5 μm saturated with niobium. Aluminum melt is introduced and this closing second process step AlS layers melt to a temperature of 950 to 1100 ⁰ C a thickness between about 1 and 10 μm, that is, is heated and, depending on the temperature, about 3 to 5 thin and flexible layers that are sufficiently thin. percent of niobium

This second process step consists of the 60 To manufacture a superconductor with one layer Feits mentioned, in that the coated niobium carrier of the A 15 phase of the system Nb-Al-Ge has it as

In an inert atmosphere for 0.5 to 5 seconds with proven particularly favorable, the Niobträgsr for BiI-

a temperature of 1700 to 1960 ⁰ C is annealed. formation of the NKMOeV layer in a to about 850 ⁰ C

Under an inert atmosphere, a non-oxy-heated melt of the composition AlJgGe ₈₁₁ Nb, dying and non-nitriding atmosphere, is to be introduced. This confess to germanium and niobium, for example vacuum or preferably saturated melt keeps at the temperature of about

Noble gas. In dian provided for the annealing temperature 850 ⁰ C, even for prolonged coating their co-Temperarurbereich 1700-1960 ⁰ C melts at the settlement. Particularly favorable for achieving higher

7 8

critical temperatures and high critical current part of the device in which the wire-shaped It is dense when the niobium carrier to form niobium carrier in the with niobium or niobium and germanium

a 1 to 2 μm thick Nb (Al, Ge) _a layer, about saturated aluminum melt is immersed and that of NbAl ₃ and Al or Nb (Al ₅ Ge) _{3 is introduced into the melt for 0.5 to 1.5 seconds} exist-

and the coated niobium carrier is provided with a layer for about 0.5 to 3 seconds. In Fig. 2 is the one at the the long in an inert atmosphere at a temperature device according to FIG. 1 crucible used

. is annealed from 1830 to 1870 ^{0 C.} shown in more detail in section. F i g. 3 shows this

A further increase in the critical current densities section of the device in which the niobium support provided with the layers of the A15 phase of the Nb-Al system and called layer at a Tempedes system Nb-Al-Ge can be achieved by io temperature from 1700 to 1960 ⁰ C is annealed,
that the inert atmosphere during annealing is used for the protection with the aid of the in F i g. 1 illustrated annealing temperature decomposable or reactive presented device, a wire-shaped niobium gas is admixed, which contains at least one of the carriers 1 by a for example made of molybdenum beElemente carbon, boron or silicon. Standing metal container 2 pulled through it, which evidently contains these elements during annealing in the passage openings 3 for this purpose. Inner-A15-Layer built in, which in turn increases the critical current density, which is half of this metal container. Melting crucible 5 provided with passage openings 4 in particular is favorable 7. to avoid excessive evaporation from high-temperature-resistant ceramic, the re-formation of aluminum is when the inert atmosphere with niobium or niobium and germanium is not a vacuum, but noble gas, Preferred * o saturated aluminum melt 6 contains. With a wise argon, serve. Such a noble gas can then advantageously have a diameter of the niobium carrier 1 to be coated up to about 4 percent by volume methane of about 0.2 mm, the openings 4 can have a diameter of up to about 2 mm or up to about 0.3 percent by volume diborane. Which are mixed. Because of its surface tension, the melt 6 cannot flow out through these openings from the A15 layer formed in the A15 layer, regardless of the installation of the elements mentioned. The cover 7 serves to close the critical temperature and the critical current density of the metal container 2 after it has been achieved by the fact that the coated and brought the melted material. The metal container 2 \ id, which has been annealed with the melting material for at least 10 hours, is inserted into a tube 8, for example a quartz tube in an inert atmosphere at a temperature between 30, which is heat-treated at both 500 and 1000 ° C. Ends by, for example, made of brass

As already mentioned, the advantages of the method according to the invention that can be cooled and, for example, be cooled by means of water, come especially when it is possible to close the caps 9. The caps 9 and 10 position of long wire or band-shaped niobium are provided with tubular passages 11 and 12 for inert with a surface layer of the corresponding niobium carriers 1. Furthermore, the Al5 phases are effective in the cap 9. The wire or tape stub pipe 13 is inserted through which the shaped niobium support can advantageously be flushed with gas continuously. Outside the tube 8 will be pulled. Particularly suitable for generating a high-frequency heating coil 14, which is used to melt an Al5 layer on such a wire or strip 40 to heat the metal container 2 to the temperature required for the shaped niobium carrier. The advantage that the metal container 2 has openings for the niobium carrier, a flat and the crucible 5 relatively small with through openings can be provided, so that when through-flow crucibles contain Metal container, a further 45 thicknesses of the wire-shaped niobium carrier of some metal bodies provided with a passage opening, meters per minute Dwell times of the carrier in each of the tubes that easily surround the metal container or the metal body melt, can be flushed with gas and are accessible for less than one second. The expansion of the metal vessel 2 of a high-frequency heating element enclosing these tubes in the pulling direction of the niobium carrier 1 can, for example, be a few centimeters in the coil for heating the metal container or the 5 °.
Metal body. Zvaa subsequent annealing of the coated

Using figures and examples, the carrier is intended to serve as FIG. 3 shows an example from

Finding will be explained in more detail. "Niobium existing metal incandescent body 20, which with a

F i g. 1 to 3 show the parts of a tubular insert 21 made of high temperature resistant

Implementation of the method according to the invention before the ceramic is provided through this tube-shaped

supplied device; The coated niobium carrier 1 will be used

F i g. Figure 4 shows pulled through for different coating conditions. The metal body 20 is

the coating of a niobium carrier on a brass cap 22 with the help of a metal

reached middle effective aluminum or aluminum rod 23 attached. The brass cap 22 is also no

minium-germanium layer thicknesses as a function of 60 of a tubular bushing 24 for the niobium

from the coating time; carrier 1 and a pipe socket 25 provided. The full

F i g. 5 shows the critical current density of a permanent annealing device obtained when ix

The supraders produced in accordance with the method according to the invention are shown in FIG. 1 shown device in place d (

letters as a function of the external magnetic field. Cap 9 and the metal container 2 the metal bowl:

The in the F i g. 1 to 3 shown device 65 per 20 with the cap 22 in the tube 8 ″ in or ai

the tube 8 is advantageously suitable for continuous production. The tube 8 is then with St.

Wire-shaped or band-shaped conductor flushed with gas after the pipe socket 25 vdederum

the method according to the invention. F i g. 1 shows the heating of the Mätau body 20 to the required

9 10

The annealing temperature is used in turn, corresponding to the A15 layer-related critical current density

F i g. 1, a high frequency heating coil 14. Conductor is a function of a perpendicular to the

The mean effective aluminum or aluminum conductor standing magnetic field in FIG. 5 shown. Germanium layer thickness when the on the ordinate of this figure is the critical current niobium carrier in the melt on the niobium carrier ge 5 dense / _c in Acm- ² , on the abscissa the magnetic layer formed depends on the temperature, on the flux density B applied in Tesla. The critical point is the melt, and the dwell time of the current density of the carrier in the melt according to the present example as well as of the assembled conductor after annealing is determined by the settling of the melt. In Fig. 4 this dependent curve 41 is shown. As curve 41 shows, the speed is shown for three exemplary cases. At the io critical current density in a magnetic field of 3 Tesla ordinate of Fig. 4 is the mean effective aluminum about 6 · 10 * Acm " ² , in a mignet field of 5 Tesla minium or aluminum-germanium layer thickness about 3.5 · 10 ⁴ Acnr ² and in a magnetic field of Sai or 3ai. Ge in μτα, on the abscissa the dwell 8 Tesla about 2.5 · 10 ⁴ Acm- ² . After the annealing time t of the niobium carrier in the melt, the superconductor was then plotted for about 240 hours in seconds. Curve 31 shows the Heat-treated in a niobium-saturated aluminum melt located at 100O ⁰ C 15 under argon at a temperature of about 750 ° C, whereby a considerable increase achieved mean effective aluminum layer thickness in the critical current density and also the critical dependence on the residence time. Curve 32 shows the temperature was achieved. the critical in a heated on HOO ⁰ C, saturated with niobium temperature, was after the heat treatment as aluminum melt obtained average effective aluminum 20 18.4 K while the critical Stromdic After the minimum layer thickness, depending on the dwell heat treatment, the values shown in FIG. 5 through curve 42 time. Curve 33 finally shows the values shown in FIG. In an externally heated Al _e , Ge ₃₀ Nb _r melt, the mean effective field of 5 Tesla achieved, the critical current density tive aluminum-germanium layer thickness, depending on the heat treatment, is about 6.5 · 10 * Acin *. dwell time. As shown in FIG. 4 can be seen 15 Both curve 41 and curve 42 take the mean effective layer thicknesses at the temperature of the liquid helium of 4.2 K, measured as the temperature of the melt increases,
as well as, especially in the range of short residence times, with increasing residence time. B is ρ ie 1 2

Using a few examples, the production of a 30th

Superconductor according to the method according to the invention A wire-shaped niobium carrier is through a

to be explained further. Examples 1 to 4 100O ⁰ C heated melt of the composition

relate to the production of a conductor with an Al ₉₈ Nb ₄ drawn, with its dwell time in the

Layer of the Al5 phase of the Nb-Al system, which melts in 0.5 seconds. During this

Play 5 to 7 the production of a conductor with a dwell time grows on the carrier from NbAl ₃ and

Layer of the A15 phase of the system Nb-Al-Ge and aluminum existing cladding with an effective

Examples 8 to 10 show the production of a conductor with an aluminum layer thickness of 1.6 μm. Who is so

according to the inventive method, wherein the layered niobium wire is then 1.6 seconds long

Inert atmosphere during the annealing at least one annealed ^{at a temperature of 1880 0 C.} Included

containing the elements carbon, boron or silicon 40 forms a 4 μm thick coat of A15 phase mil

ting gas is added. a critical temperature of 16.6 K and a

In all examples, a niobium-critical current density of 2.2 · 10 ⁴ Acm ^{2 is used as the niobium carrier}

wire with a diameter of about 0.2 mm has a magnetic field of 5 Tesla. By then about

turns. Further, for the coating and annealing of the annealing for 240 hours under argon at one

Niobium carrier in the F i g. 1 to 3 shown before 45 temperature of about 700 ⁰ C, the critical temps direction is used. The niobium wires, the 100 and more ratur to 18.5 K and the critical current density it

Meters long, were continuously generated by a magnetic field of 5 Tesla to 4 6 · 10 ⁴ Acm " ²

passed through the device. increases

example 1

i> ^ y τ. ». = · j -.L · ~ ^ · -,.,. Example 3

The niobium carrier is at a speed of

3.1 "m / min through a heated to 1000 ⁰ C melt a wire-shaped Niobträger is an au!

der Zasammeasefaaag Al ^ Nb ₄ hmdüffifazug. The UOO ⁰ C heated melt of the composition Verweflzert m the melt is about Al ₉₅ Nb ₅ drawn, with its residence time in de. 0.4 seconds. During this dwell time, melt is produced. During this period, the core of the niobium wire is surrounded by a ring of NbAl ₃ - while a ring of NbAl ₃ and Knstaüitea and elementary Ahimnmun is formed on the support. The aluminum-aluminum existing layer, which is effective as a result, has an average thickness of 1.6 μm or the total length of an average factor. The wire-shaped carrier coated in this way is then annealed for 2.1 seconds at 1880 ° C for 2.1 seconds , 6 K unc SLjT ^ rZ ^ ? S * £ ^ Wt *** ^ ** ⁵ * current density inrinem Mapietfeld

* ^^^^ • WAcm- '. Durcheineet ^ alOaStffli ⁵ ** * "*" ** Wound treatment under argon be * "* ⁷⁰⁰ ° ^C ™ ^{d the} critical temperature dis * **** ^{f ltJ5 K di} di

d sicm am aem iNioonagerem s, * pm starter about 700 ⁰ C, the critical temperature dia «from Ä15-Pii3se ücs Systems rio-Al with dncr Xjöters on ΐίΐ s ir λ a * ^ - ^ *"", ^^ mHirbte be m temperature of about 16.6 K. The increase to the 5 Tesla to 4.3 * · 10 «Acm ^ *

Example 4

A wire-shaped Niobträger ₉₆ is pulled through a heated Nb ₄ to 1000 ⁰ C melt of the composition Al, its residence time is 0.6 seconds in the melt. During this dwell time, a _{layer consisting of NbAl 3} and aluminum forms on the carrier, which corresponds to an average effective aluminum layer thickness of 1.8 μm. The carrier coated in this way is ^{calcined at a temperature of 1700 °} C. for 2.1 seconds. This forms a 3.5 μm thick layer of the A15 phase with a critical temperature of 16.6 K and a critical current density at 5 Tesla of 1.2 · 10 ¹ Acm ² . A subsequent heat treatment for about 240 hours under argon at about 700 ° C. increases the critical temperature to 18.5 K and the critical current density at 5 Tesla to 2.2 · 10 ¹ Acm ² . In this example, as in Examples 1 to 3, the wire was annealed under argon. *O

Example 5

A wire-shaped niobium carrier is pulled at a speed of 1.8 m / min through a melt of the composition AlgSGe ₃₀ Nb ₁ »5 heated to 850 ° C. This speed corresponds to a dwell time of the wire in the melt of about 0.7 seconds. During this dwell time, a uniform, 1.5 μm thick sheath of NbAl _a , ₇ Ge _0g3 is created around the wire. The coated wire is then ^{annealed at about 1830 °} C. under argon. For this purpose, it is pulled through the niobium incandescent body 20 at a speed of 1.2 m / min. This speed corresponds to a reaction time of 1.5 seconds. During this reaction time, a 2.5 μm thick layer of the A15 phase of the Nb-Al-Ge system with a composition of about Nb ₃ (Al _0- ^ Ge ₀ ,,) forms around the niobium core of the wire - over this layer there is a thin, 0.3 μm thick layer of the σ phase and above it an approximately 0.2 μm thick zone which contains several phases, in particular the Al5 phase and the σ phase and a phase with the composition Nb ₅ ( GcAl) ₃ . The superconducting properties of the 2.5 μm thick layer of A15 phase are not impaired by the very thin overlying layers from the other phases. The layer from the A15 phase has a critical temperature of 17.3 K and a critical current density in a magnetic field of 5 Tesla of 1.2 · 10 * Acm ~ *. As in the other 5 examples, the critical current density is measured at 4.2 K. in each case. By an additional approximately 190 hours long heat treatment under argon at about 750 ⁰ C, the critical temperature of the conductor to 19.3 K and the critical current density at 5 Tesla to 1.8 * -10 Acm "is increased

Example 6

A wire-shaped Niobträger is pulled through a heated at 850 ⁰ C melt of the composition Al ₈₉ Ge ₃₀ Nb _x, its residence time is about 0.7 seconds in the melt during this Verweflzeit a sheath of NbAIj ₁₇ Ge ₀₁₃ is formed on the Niobträger, which corresponds to a mean effective aluminum-germanium layer thickness of 1.4 μm. The wire coated in this way is then annealed for 0.6 seconds at 1855 ° C. under argon. A 2.8 μm thick layer of the A15 phase is formed around the wire core of the Nb-Al-Ge system with a critical temperature of 17.5 K and a critical current density at 5 Tesla of 1.7 · 10 ⁴ Acm- ² . The critical temperature of the conductor is increased to 19.3 K by a heat treatment for about 190 hours at about 700 ^{° C. under argon.}

Example 7

A wire-shaped niobium carrier is drawn through a melt of the composition Al ₈₉ Ge ₃₀ Nb ₁ heated to 850 ° C., its residence time in the melt being about 0.7 seconds. An NbAl ₂ ,, Ge ₀ , ₃ jacket, which corresponds to an average effective aluminum-germanium layer thickness of 1.4 μm, is formed on the niobium carrier. The carrier coated in this way is ^{annealed under argon at 1855 C} C for one second. This creates a 3.4 μm thick layer of the A15 phase of the Nb-Al-Ge system with a critical temperature of 17.2 K and a critical current density at 5 Tesla of 3.0 · 10 ⁴ Acm ² . A subsequent heat treatment for about 190 hours under argon at about 700 ^° C. increases the critical temperature of this conductor to 19.0 K and the critical current density at 5 Tesla to 4.2 · 10 ⁴ Acm ² .

Example 8

A drahtförmager Niobträger ₉₆ is pulled through a heated Nb ₄ to 1000 "C melt of the composition Al, its residence time is 0.4 seconds in the melt. During this time forms on the Niobträger a layer of NbAl ₃ and aluminum which a mean effective aluminum layer thickness of 1.1 corresponds μιη. then, this wire is annealed 1.6 seconds at a temperature from 1880 ⁰ C. the annealing is carried out under argon, 1.5 volume percent methane are added. To an appropriate methane replenishment To achieve this, the gas mixture is allowed to flow, for example at a throughput rate of 200 l / h, through the quartz tube in which the metal incandescent body 20 shown in Fig. 3 is located , 6 μm thick layer of the A15 phase of the Nb-Al system, with carbon being built into this layer as well as into the niobium carrier of the support and the layer of carbon after the reaction is about 0.2 atomic percent. After annealing, the A15 layer formed shows a critical temperature of 16.5 K and a critical current density at a magnetic field of 5 Tesla of 13 · 10 * Acnv ^a . By a subsequent about 240 hours long heat treatment at 750 ⁰ C under argon, the critical temperature was raised aul 18.3 K and the critical current density at 5 Tesla aui 26 * 10 * ² Acm

Example 9

A wire-shaped Niobträger is pulled through a heated AU 1000 ⁰ C melt of the Al Zusammensetzunj _M Nb _4, its residence time is 0.4 seconds de melt, this forms au the wearer be made NbAl, and aluminum-standing layer having an average effective Ak minium layer thickness of 1.1 lim. Various parts of the carrier coated in this way are then j <Weils for about one second under argon at 1880 ° >

13 14

annealed. The various admixtures as well as the through

Amounts of methane mixed in. The respective critical temperatures achieved by these admixtures

Methane quantities as well as the critical temperature and temperatures and critical current densities in a magnet

the critical current density in a magnetic field of 5 Tesla that is generated during the reaction time

5 Tesla of the 5 formed, 2.6 μm thick layers of the Al5 phase of the formed during this reaction time

2.6 μπι thick layer of A15-Pliase of the system TNb-Al are given in the following table 2

Nb-Al are given in Table 1 below. ben. The table also shows the critical ones

The table also shows the critical temperatures and critical current densities,

doors and critical current densities at 5 Tesla are connected by a glow following the glow, for example

given by additional heat treatment under argon for about 100 hours

Allow long heat treatment of the respective conductor at about 700 ^° C. to be achieved.
Argon at a temperature of about 700 ⁰ C reached

became. Table 2

CH ₄ to After glow Λ in 10 «
Acm ~ * After heat treatment "C sentencein 2.8 lung at 700 ' /one
10 «Acm- * Volume -
piozent TV in K 3.5 r _c inK 5.4 0 16.3 4.9 18.3 6.0 0.1 16.3 6.4 18.3 7.6 0.3 16.3 9.0 18.2 10.5 0.8 16.3 10-16 18.0 17.9 1.9 16.3 18.1 14-28 > 3.0 about 16.3 about 18.0

Β, Η, -Za-
* o sentence in After glow /one After heat treatment ever in
10 «Acm- ¹ percent 7c in K 3.8 7UnK 7.8 0 16.4 7.5 18.1 12.4 *> 0.03 16.0 6.5 17.6 14.0 0.05 16.1 6.2 17.6 12.9 0.06 16.2 4.3 17.6 8.8 0.09 16.5 4.0 17.7 8.5 0.25 16.6 18.2

As Table 2 shows, are also due to the admixture from diborane to argon during glowing As Table 1 shows, the admixture can lead to substantial increases in the critical current density from methane to the argon atmosphere in the glow. Particularly high Irish current densities critical current densities of the conductors 30 produced are sufficient with additions of diborane between 0.03 and can be increased significantly. Another increase is 0.06 percent by volume.

is given by the subsequent heat treatment. By adding silicon-containing gas », e.g. B.

The addition of methane should advantageously not exceed 4% silanes; similar improvements can be achieved amount, since with higher additions it is sufficient.

still has very high critical current densities - 35 As well as being suitable for coating wires occur, the niobium carrier through carbide precipitates, of course, the method according to the invention as well however, increasingly embrittled. for coating ribbon-shaped niobium conductors with

_n , layers of the A15 phase of the systems Nb-Al and

Example 10 Nb-Al-Ge. As a result of the with niobium or with niobium

A wire-shaped niobium carrier is drawn through an aluminum melt, which is saturated to 4 ° and germanium, the 1000 ° C heated melt with the composition Conditions for the coating of the niobium carrier Al _M Nb «, whereby its dwell time remains unchanged over a long period of time. 4 seconds. On the carrier, the method according to the invention also forms very large carriers with a _{length consisting of NbAl 8} and aluminum, for example carrier several kilometers long, with a layer. a medium effective aluminum 45 can be coated continuously. A layer thickness of 1.1 μm is also suitable. Various portions method of the invention also are used to Beschichdieses so coated substrate each about tung Niobträger differently shaped, for example, for one second under argon at a temperature sheets or cylinders, which are then annealed for coating 188 O ⁰ C. Various amounts of diborane (B, H ”) are added to the argon, expediently immersed in the melt. 50 den can.

For this purpose 2 sheets of drawings

Claims (12)

Patent claims: ; 1. A method for producing a superconductor S Mt a layer of the A 15 phase of the * system j ^ brAl or Nb-Al-Ge, in which a niobium carrier in an ^{aluminum heated to a temperature of 800 0} C and more? or Aluiainium-Gerraanium melt introduced and then m inert! Atmosphere jeiner Qlühbehandlung subjected at a temperature above 800 ⁰ C, characterized in that the Niobträger heated by introducing in a 800 to 1400 ° C, saturated with niobium or niobium and germanium aluminum melt or with one of NbAl ₃ and Al, ^ us; J ^ b (Al ₅ Ge) ₃ existing, 0.5 to 5μώ thick layer is provided and the subsequent annealing treatment of the carrier coated in this way at a temperature of 1700 to 1960 ⁰ C lasts for 0.5 to 5 seconds. 2. A method for producing a superconductor with a layer of the A15 phase of the Nb-Al system according to claim 1, characterized in that the niobium carrier is provided with a layer consisting _{of NbAl 3 and Al by introducing it into the aluminum melt saturated with niobium} Al content corresponds to an average effective aluminum layer thickness of 1 to 2μηι, and that the niobium substrate coated in this way is annealed in an inert atmosphere for 1 to 3 seconds at a temperature of 1700 to 1900 ⁰ C. 3. The method according to claim 2, characterized in that the coated niobium carrier is annealed at a temperature of 1870 to 1900 ⁰ C. 4. The method according to claim 2 or 3, characterized in that the niobium carrier for coating is introduced for 0.1 to 0.5 seconds into the aluminum melt saturated with niobium and that this melt is heated ^{to a temperature of 950 to HOO 0 C and} contains about 3 to 5 atomic percent niobium, depending on the temperature. 5. A method of manufacturing a superconductor with a layer of the A15 phase of the system Nb-Al-Ge according to claim 1, characterized in that the Niobträger for the formation of Nb (Al, Ge) ₃ layer in a ⁰ C to about 85O heated melt of the composition Al ₆₉ Ge ₃₀ Nb _{1 is} introduced. 6. The method according to claim 5, characterized in that the niobium carrier to form a 1 to 2μηι strong Nb (Al, Ge) ₃ layer is introduced into the melt for about 0.5 to 1.5 seconds. 7. The method according to claim 6, characterized in that the coated Niobträger is annealed for about 0.5 to 3 seconds in an inert atmosphere at a temperature of 1830-1870 ⁰ C. 8. The method according to any one of claims 1 to 7, characterized in that the inert atmosphere during annealing one containing at least one of the elements carbon, boron or silicon, decomposable or reactive gas is added at the annealing temperature. 9. The method according to claim 8, characterized in that the inert atmosphere of noble gas, preferably argon, and this up to about 4 percent by volume methane or up to about 0.3 percent by volume of diborane are added. 10. method of any one of claims 1 to 9, characterized in that the coated and annealed Niobträger is still at least 10 hours heat-treated in an inert atmosphere at a temperature between 500 and 1000 ⁰ C. ' 11. The method according to any one of claims 1 to 10, characterized in that a wire or band-shaped Niobium carrier is continuously drawn through the melt and an annealing device. 12. Device for performing the method according to claim 11, characterized by one with passage openings (3) for the niobium carrier (1), one also with passage openings (4) provided crucible (5) containing metal container (2), another with a metal body (20) provided with a passage opening, one each for the metal container (2) or the Metal body (20) enclosing pipe (8) which can be flushed with gas and one pipe each enclosing these pipes High-frequency heating coil (14) for heating the metal container or the metal body.