DE1458478A1 - Process for the preparation of the intermetallic compound niobium-tin - Google Patents

Description

fir Lanzen, June 26, 1964

AktiontT ": - c; l 1.-Ch-nf t Werner-von-Siqmens-S.tr. 50

PLA 64/1396

[Dr. ExpL

Process for the preparation of the intermetallic compound niobium-tin (Nb _x Sn)

Di ο ;; upraloi fm de intermetallic compound niobium-tin (Nb ^ Sn) has a transition temperature of about 18 K. Since this connection, in addition to the high transition temperature, 'also otherwise good superconductivity'; igeh: 5chH.f fco η heats up, for example a high critical magnet field, is a representation of this compound in abundance and Purity urgently required for environmental and technical purposes. Wires and ribbons au ;; Niobium-tin can be used, for example, for the manufacture of superconducting coils for the production of strong M'igrie tfeldf-r can be used.

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However, niobium-tin cannot be chemically easily chemically because _r r _Tc . _v put. For a long time they made do with metallurgical sintering processes. Niobium and tin are mixed in a stoichiometric ratio and sintered at a high temperature. Dan so won. The material is very porous and brittle; its superconducting properties can depend on the sintering temperature. The technical application of sintered niobium-tin is severely hindered by such material properties. .

The intermetallic compound niobium-tin was presented by Hanak for the first time on a purely chemical basis (French patents 1,322,694 and 1,322,777). It was represented by the simultaneous reduction of gaseous chlorides of niobium and tin by means of hydrogen at temperatures between 900 and 1200. ⁰ G ... Hm-ik gives three different methods in the two patents mentioned to obtain niobium-tin by a gas phase reaction . ·

According to the first method, niobium pentachloride (NbClc-) and tin- _; dichloride (SnClp) evaporated in a reaction vessel. The a.iforinigen compounds are transported with the help of an inert gas into a Lt? Iß.e zone of the reaction vessel and reduced there by 'Vaor.erGtoff. Solid material separates out.

In the second method proceeds analogously, except that instead of stannous chloride (SnCIp) of tin tetrachloride (SnCl ₄₎ as a starting-smateri ¹ '! chosen,... ; . .

In order to achieve an approximately stoichiometric composition of the end product ·.: - Niobium-tin , a solitaire must be used. the starting material

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which the chlorides of niobium and tin are evaporated to keep them constant the vapor pressures are precisely controlled. When carrying out the process, according to these methods, three temperatures must be kept running monitored, namely the temperatures of the two zones of the reaction vessel in which the starting materials are located.

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den, and the temperature of the reduction zone.

These disadvantages are avoided in Hanak's third method. This method uses sintered niobium-tin in powder form as the starting material. The entire reactor is heated to 1,000 to 1,200 ⁰ C. A stream of chlorine gas is passed over the niobium-tin powder, forming gaseous niobium pentachloride (NbClj-) and tin tetrachloride (SnCl.), Which is reduced in a reaction zone by the introduction of hydrogen. The reaction proceeds according to the equation

3 NbCl _c + SnCl. + Q _t 5 H ₀ * Nb, Sn + 19 HCl.

τ 4 I 3

By adding hydrogen chloride gas to the hydrogen stream According to Hanak, the reaction can be controlled.

These investigations have now indicated that the third of Hanak specified method is associated with disadvantages.

These experiments showed that the reduction of tetravalent tin in tin tetrachloride (SnCl.) With hydrogen does not completely precede the given equation, but for the most part only leads to divalent tin, that is to say to tin dichloride (SnCl ₀ ^ ,, which is no longer reduced. This has the consequence, ■ j'i ..- " \ '\ ~ ibftoi'chiHelene X ^T iob-Zinn ir.it''' ■ '■ ■ * ■""

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too low a tin content occurs. The lack of tin again has the effect that the jump point of the product obtained by the process mentioned is considerably below the jump point of the approximately stoichiometrically composed compound Nb, Sn, that is, considerably below 18K. - _φ

The "invention provides a. Method for the preparation of the intermetallic Compound .Niobium-tin (Nb, Sn) ■ by reducing the chlorides de: Comporvents this compound by means of hydrogen in one reaction: vessel, which avoids the disadvantages of the Hanak method.

The invention consists in that the chlorides to be reduced by Niobium and tin are heated by passing hydrogen chloride gas over them tes starting material, which consists of niobium and tin, can be obtained.

In attempts to influence the reaction equilibrium with Hydrogen chloride gas in a process corresponding to the third method given by Hanak did not release the hydrogen chloride at Hanak it was associated with the hydrogen stream, but with the chlorine gas stream Surprisingly, it was found that even when the chlorine gas flow is completely blocked, that is, when pure ChI is transferred hydrogen over the heated niobium-tin, in the reaction zone never Tin was deposited »

As a starting material · sintered niobium-tin was 3 a.tom? Iiob and 25 atomic% \ used in Tablcttenforr with a composition of about 75 miles. An examination of the deposited material is carried out,

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the superconductivity starts at about 18 ^° K. The transition curve /, is relatively steep. The jump point is about T7,5 ⁰ K, which is higher than Paraten in the produced chlorine gas pre- '. "'' ■. ·

A detailed investigation of the reaction mechanism showed that when hydrogen chloride gas is passed over NiοTj tin the lower valence chlorides are formed, namely tin dicloride (SnCl ₂ ) and niobium trichloride (NbCl ₃ ). The reaction equation is:

Nb ₃ Sn + T1 HCl <= ± SnCl ₂ + 3NbCl ₃ + 5.5

These chlorides are almost completely reduced by hydrogen. The niobium-tin formed therefore contains more tin than that produced by reduction material obtained from tin tetrachloride (SnCl.). The jump point is therefore closer to the expected value of 18 K.

The inventive method also has the advantage that. · hydrogen chloride gas is much easier to handle than chlorine gas. .

t) The transition temperature of the gas phase obtained by reduction. '<Material, according to another invention, be further increased in that * instead of a Ausgangsmaterialα with a composition "of 75 atomic? £ niobium and 25 atom $ tin a starting material. Used" which has a higher content of tin.. ■ ·

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The following should be noted:

The composition of the intermetallic compound kiob-tin: becomes, *. only approximately reproduced by the formula Nb, Sn. In fact, ¹ this is the ß-tungsten (A 15) phase of the niobium-tin system, which has a relatively broad area of existence and whose chemical composition can vary between Fb ^ Sn and Fb.Sn. The transition temperature depends on the tin content. Sprung' temperatures of 18 ⁰ C were measured at the sintered specimens having the composition of about Fb, Sn. The gas-phase preparations obtained by passing hydrogen chloride over such sintered material and reducing the chlorides formed have a somewhat lower tin content. This tin deficiency is due to the fact that fiob trichloride is reduced somewhat more easily than tin dichloride during the separation from the gas phase. The material deposited from the gas phase is therefore somewhat lower in tin than the starting material. This deficiency can be eliminated by increasing the tin content of the starting material.

A suitable starting material rich in tin can be, for example, in Made the way that sintered fiob tin wheel. 1? one A composition of about 75 atomic $ niobium and 25 atomic $ tin grind, -added with additional tin, pressed into tablets and then sintered again. A tin content of the starting material - '"" - ■ " from about 30 to -40 "atom - # has been found to be beneficial.

The "method according to the invention is suitable for the production of solid niobium-tin and also for the production of niobium-tin layers on -" - "· support materials, in particular on metallic wires or strips,

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Tin dichloride and niobium trichloride are formed when hydrogen chloride gas is passed over niobium-tin safely at temperatures from 400 C. The starting material is therefore heated to a temperature between 400 and 1000 ^° C.

The Abseheic'ungszone is preferably maintained at a temperature of about 800 to 900 ⁰ C. When strips or wires are coated, they are heated ^{to approximately 800 to 1100 °} C., preferably to approximately 900 ^{° C.}

The method according to the invention is to be explained in more detail with the aid of a few figures and examples. ·

Pig. 1 shows schematically an embodiment of the reaction tube for carrying out the method according to the invention.

Fig. 2 shows schematically a. Embodiment of the entire system for carrying out the method according to the invention.

3 schematically shows an exemplary embodiment of a top view Device for depositing the superconducting compound niobium-tin on wire- or band-shaped metallic carriers according to the method according to the invention. ■

The reaction tube according to FIG. 1 consists essentially of a quartz tube 11 into which a second, thinner tube 13 is inserted with the aid of a ground joint 12, which tube extends approximately to the middle of the tube 11. On the end of the tube 13 a .short upper throw piece 14 is placed on which the reacted reaction material can be reflected. Through the inlet port 1 _V 5, gas can flow into the inner pipe 13 through the inlet port 16, independently of it, into the outer pipe

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Tube 11 are blown. The residual gases can through the pipe socket 17 be discharged. The solid starting material is located in the pipe 13 18 of the reaction.

The arrangement of Fig. 2 consists of that in Pig. 1 shown in detail Reaction tube 21, which is placed in a tube furnace 22, from "three grass bins 23» 24 and 25 and from the connecting pipelines 26 and 27. The pipeline 27 branches into the line

lines 28 and 29. Through the pipe 30 die.Restgase can be discharged will.

The device according to FIG. 3 consists essentially of a quartz tube 31 with two smaller pipe sockets 37 and 38 and a larger one Pipe socket 35 in which the solid Aungango material 36 of the reaction is located. The quartz tube 31 has graphite bodies at both ends 32 and 33 closed, which are each provided with a bore for the implementation of the wire-shaped or band-shaped carrier 34. The carrier is unwound from the spool 40 and after coating wound on the spool 4I. The carrier stands with the graphite bodies 32 and 33 in conductive connection. These are connected to an electrical power source via leads 43 and 44. The reaction tube 31 is located in a suitably shaped, for example, a hinged tubular furnace 42 which also encloses the pipe socket 35. The superconducting connection will be roughly at the point 39 deposited on the carrier 34.

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example 1

In this example, the preparation of crystalline niobium-tin according to the method according to the invention with the aid of the devices shown in FIGS. 1 and 2 is described in more detail. <

The starting material 18 is inserted into the inner tube 13 of the reaction tube 21 in the form of presintered niobium-tin tablets. Thereafter, the reaction tube 21 is heated in the tube furnace 22 to a temperature of about 800 ⁰ C. During the heating period, an inert gas, for example argon, is introduced into the reaction tube 21 from the gas container 25 through the pipes 28 and 27 and the inlet connection 15, and hydrogen from the gas container 24 via the pipe 26 and the inlet connection 16. The air is expelled from the reaction tube 21 in the process. When the air is completely displaced from the reaction tube 21, and the pipe has reached a temperature of about 800 ⁰ C, the argon flow is interrupted and. from the gas bottle 23 via the pipes 29 and 27 and the inlet port 15 hydrogen chloride gas introduced into the reaction tube. When the hydrogen chloride gas flows over the starting substance 18, Nio.b and tin are simultaneously converted into niobium trichloride (NbCl) and tin dichloride (SnCl ₂ ). Both compounds are gaseous at the temperature of 800 ° C. in the reaction tube. The hydrogen entering at the coupling piece 14 through the outer tube 11 causes the reduction of the chlorides to the metals. The niobium-tin formed is deposited on the quartz wall of the cap piece 14. The residual gases are discharged through the pipe socket 17. After the reaction has ended, the deposited niobium tin can be treated with a -

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Mixture of concentrated (40 ^ iger) hydrofluoric acid and water in proportion of about 1: 5 can easily be detached from the quartz wall.

The smaller the niobium-tin that is produced, the better it is the flow rate of the hydrogen chloride gas in the reaction tube is chosen. The amount of hydrogen chloride gas required per unit of time depends of course on the size of the 'reaction tube away. In the present example, a length of about 60 cm and a diameter of about 2.5 cm was chosen for the inner tube 13. With a hydrogen chloride throughput of 3 to 4 l / h. were there good reaction products achieved.

Example 2

According to the invention, the deposition of niobium-tin can not only take place in one Quartz tube, but on various suitable carrier materials. For example, superconducting wires or tapes be produced in that the superconducting connection on wire-shaped or strip-shaped metallic carriers, for example a Nickel-iron alloy, which contains about 75% by weight of nickel, or made of gold-plated nickel is deposited.

In this example, the deposition of niobium-tin should be based on FIG on a tape made of said nickel-iron alloy according to the method according to the invention.

The starting material 36 is in the form of sintered niobium-tin tablets introduced into the pipe socket 35. Furthermore, the nickel

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Iron tape 34 inserted in a suitable manner into the quartz tube 31 and pulled through the tube at a constant speed of about 15 cm / min. Electric current is passed through the belt 34 via the supply lines 43 and 44 and the graphite bodies 32 and 33, which is dimensioned such that the belt is heated ^{to a temperature between approximately 800 to 1100 °} C., preferably to 900 ^{° C.} The tube furnace 42 is brought to a temperature of about 600.degree. As a result, on the one hand, the starting material 36 is heated and, on the other hand, it prevents precipitates from forming on the wall of the reaction tube. After the air in the reaction tube 31 has been displaced, hydrogen chloride gas is introduced through the pipe socket 35. The gaseous chlorides of niobium and tin then form over the starting material 36 and are forced into the reaction tube 31 by the subsequent hydrogen chloride. At the same time, hydrogen is introduced into the reaction tube 31 through the pipe socket 38. In the immediate vicinity of the hot strip 34, the chlorides of niobium and tin are reduced as a result. The niobium-tin formed is deposited on the strip 34 approximately in the vicinity of the point 39. The coated tape is wound onto the motor-driven reel 41. The residual gases are discharged through the pipe socket 37.

The reaction tube 31 was about 1 m long in the present example and chosen with a diameter of about 3 cm. The hydrogen chloride gas flow rate was about 3 to 4 liters per hour.

In addition to metallic wires and strips, other carrier materials, for example metallic or ceramic components with a niobium-tin layer be coated.

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Claims (1)

^ '- "* PLA 64/1396 · ^{: r 4} - claims . . - * ". 1. Process for the preparation of the intermetallic compound niobium-tin (Nb, Sn) by reducing the chlorides of the components of these Connection by means of hydrogen in a reaction vessel, thereby marked that. the chlorides of niobium and zinc to be reduced by passing hydrogen chloride gas over heated starting material, which consists of niobium and tin, can be extracted- 2. The method according to claim 1, characterized in that the starting material is heated to a temperature between 400 and 1000 ⁰ C. 3. The method according to claim 1 or 2, characterized in that the Zone of the reaction.T vessel in which the deposition of the niobium-tin takes place, is heated to a temperature between about 800 and 900 C. Φ. Method according to claim 1, 2 or 3 _r, characterized in that ei; Starting material with a tin content of more than 25 atom ^ is used » 5. The method according to claim 4, characterized in that a starting material used with a tin content of about 30 to 40 atomic £ will. ). Method according to one of the * Claims 1, 2, 4 or 5, characterized in that that the superconducting compound Kiob tin on wire or tape-shaped carriers made of suitable metal is separated. 8098 13/0584 SAD OWGlNAL -.- ¹ ■, * ^J PLA 64/1396 ·,. ^ •; · - ■ "'^' U58478 ' \ 7. The method according to claim 6, characterized in that the wire-- ^; or belt substrate is heated to about 800 to 1100 ⁰ C. 8. The method according to claim 7, characterized in that the wire or strip substrate is heated to about 900 ⁰ C. 9. The method according to any one of claims 6, 7 or. 8, marked thereby net that a band-shaped carrier made of a nickel-iron alloy with about 75% by weight nickel content is used. _ 13 - Kb / Kff 809813/0584