JP2549698B2 - Method for producing oxide-based superconducting wire - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a superconducting wire used in a superconducting device such as a superconducting magnet coil or a power transportation line.

"Prior Art" Recently, various oxide superconductors have been discovered in which the critical temperature (Tc) at which the normal conduction state transitions to the superconducting state is equal to or higher than the liquid nitrogen temperature. This type of oxide-based superconductor has the general formula AB-Cu-O (where A is La, Ce, Yb, S
c, Er, etc. III Group a element of the periodic table and Bi, Sb etc. periodic table V b group 1 or more, B is Ba, Sr etc. periodic table
IIa represents one or more elements of group a)).
Then, in order to manufacture a superconducting wire including such an oxide superconductor, for example, the powder containing the group IIIa element, the powder containing the group IIa element, and the copper oxide powder are mixed and mixed. Prepare powder and fill the metal tube with this mixed powder, or fill the metal tube with superconducting powder obtained by subjecting the mixed powder to heat treatment, and then draw the metal tube with a die or the like after drawing to obtain the desired The wire having the diameter of is obtained, and the wire is heat-treated to cause the solid-state reaction of the respective elements of the powder compact inside.
A method of obtaining a superconducting wire by producing a superconducting substance inside a metal tube is known.

[Problems to be Solved by the Invention] By the way, in the method for manufacturing a superconducting wire, since the diameter of the metal tube is reduced by the drawing process using a die and the mixed powder is compacted, there is no disconnection during the drawing process. There is a problem that the compaction density of the powder cannot be sufficiently increased because it is necessary to process the powder to a certain degree and thus the processing rate is limited. Then, as a result, the green compact having insufficient compact density is subjected to heat treatment and sintering, so that in the obtained superconducting wire, the solid-phase reaction of each element tends to be insufficient. In addition, there is a problem that the porosity of the sintered body becomes large and a superconducting wire having excellent critical current characteristics cannot be obtained.

Furthermore, when heat-treating the superconducting precursor powder or the superconducting powder to generate the superconductor, there is no gap between the metal tube and the superconducting precursor powder or the superconducting powder,
Since oxygen is not sufficiently supplied to these powders, there is a problem that the amount of oxygen in the obtained superconductor is not sufficient, and thus a superconducting wire having desired superconducting properties cannot be produced.

The present invention has been made in view of the above problems, and an object thereof is to provide a method for producing an oxide-based superconducting wire having a high critical temperature and an excellent critical current density with a high sintering density. It is in.

[Means for Solving the Problems] In the manufacturing method according to claim 1 of the present invention, after coating the superconducting precursor powder or the superconducting powder on the metal base line, the coating layer is vibrated or the like. Heat treatment is performed at a high temperature so that it does not come off or powder falls into an insert body, and one surface of a separately prepared metal tape is roughened, and then the roughened surface is oxidized to form a coating body. In order to solve the above-mentioned problems, the insert is coated with the coating so that the oxidation-treated surface of the coating is on the inside to form a composite, and then the composite is subjected to heat treatment to form a superconducting wire. It was taken as a solution.

Further, in the manufacturing method according to claim 2 of the present invention, after coating the superconducting precursor powder or the superconducting powder on the metal base line, the coating layer is heated to a temperature that does not peel off or fall off due to vibration or the like. Then, heat treat it as an interposer, roughen one side of a separately prepared metal tape, then oxidize the roughened side, and then form an oxidizer layer on the oxidized side. As a coating, the above-mentioned intercalation body is coated with the coating so that the surface on which the oxidant layer of the coating is formed is the inside, and then the composite is subjected to heat treatment to obtain superconductivity. The use of a line was taken as a solution to the above problems.

Hereinafter, an example of the method for producing an oxide-based superconducting wire according to claim 1 of the present invention will be described in detail with reference to the drawings.

First, as shown in FIG. 1, the superconducting precursor powder or the superconducting powder is coated on the metallic base line 1, and then the coating layer is heat-treated at a high temperature so that the coating layer does not drop off or fall off due to vibrations or the like. The layer 2 is formed and the interposer 3 is produced. Here, the base line 1 may be either solid or hollow, and its material is copper, silver, nickel,
Metals such as tungsten, zirconium and titanium are preferably used. As a method of forming the superconductor precursor powder or superconducting powder coating covering layer 2, for example, the case of manufacturing a Y-Ba-CuO-based superconductor, Y ₂ O _3, BaCo _3, a predetermined ratio of powder CuO And heat-treating at 500-1000 ℃ to make a calcined body, then crushed to obtain the superconducting precursor or 500 ℃ -100
Superconducting powder obtained by heat treatment at 0 ° C. is used to form it on the base line 1 by various methods such as electrophoretic deposition, and then the coating is heated at a high temperature to the extent that it does not come off or fall off due to vibration. Is heat treated to form a coating layer 2 of a superconducting precursor or a superconductor.

In order to form the coating layer 2 of the superconducting precursor or superconducting powder on the base line 1 by the electrophoretic deposition method, first,
As shown in the figure, it is immersed in the electrodeposition liquid 5 in the electrodeposition tank 4 to make it a cathode, and a DC voltage is applied between this and the anode 6.
As the electrodeposition operation, either the fixing pressure method or the fixing flow method may be adopted.When the constant voltage method is adopted, a DC voltage of 20 V or more is applied, and when the constant current method is adopted, Has a current density in the range of 0.05 to 5 mA / cm ² . As the electrodeposition liquid 5, an oxide-based superconductor powder or an oxide-based superconductor precursor powder dispersed in a dispersion medium is used. The above-mentioned oxide superconductor means the general formula AB-Cu-O (where A is an element of Group IIIa of the periodic table such as La, Ce, Yb, Sc, Er and Bi, Sb). And B represents one or more elements of Group IIa of the Periodic Table such as Ba, Sr, etc.). The composition of each constituent element of the oxide superconductor is, for example, in the case of Y-Ba-Cu-O system, Y: Ba: Cu: O = 1: 2: 3: (7-
δ), and δ is in the range of 0 ≦ δ ≦ 5. And
As the powder of this superconductor, those having a particle size of about 0.1 to 50 μm are used, and particularly fine powder of about 0.1 to 5 μm is used.
It is preferably used because a denser electrodeposition layer can be obtained. Also, in fabricating the superconducting powder, for example, in the case of the Y-Ba-CuO system, first, the respective raw material powders of Y ₂ O ₃ and BaCO ₃ and CuO, Y: Ba: Cu = 1: 2 : 3 (molar ratio) to be mixed uniformly to form a mixed powder, and then this mixed powder is calcined in an oxygen atmosphere at 500 to 1000 ° C for 1 to several tens of hours to form a calcined powder, and then This calcinated powder is subjected to a series of operations of compacting → heating → crushing once or twice or more,
A superconducting powder having a composition of Y ₁ Ba ₂ Cu ₃ Ox is obtained. In this case, it is desirable that the heat treatment performed after producing the calcined powder is performed at 800 to 1000 ° C. for 1 to several tens hours in an oxygen atmosphere. The method for producing the superconductor powder is not limited to the above powder mixing method, and a coprecipitation method or a sol-gel method may be used.

Also. As the material powder of the oxide-based superconductor, the calcined powder which is an intermediate substance for obtaining the superconductor powder is used.

Further, although acetone is preferably used as the dispersion medium, other organic solvents such as an acetone-based mixed organic solvent such as an acetone-ethanol mixed solution or an acetone-xylene mixed solution are also preferably used.

When a DC voltage is applied between the cathode and the anode 6 under such conditions, the superconductor powder or precursor powder dispersed in the electrodeposition liquid 5 is positively charged, and the base line which is the cathode 1, a dense electrodeposition layer 7 made of superconductor powder or precursor powder as shown in FIG. 1 is formed on the surface of the base line 1. Then, electrodeposition for a predetermined time,
After forming the electrodeposition layer 7 having a desired thickness, the base line 1 is pulled up and further dried with hot air to remove the dispersion medium (organic solvent) such as acetone remaining on the surface portion thereof, and further at about 900 ° C. If the heat treatment is performed for 1 hour, the coating layer 2 of the superconducting precursor powder or the superconducting powder, which is dense and uniform as a whole, is formed without uneven thickness on the surface.

Separately from the production of the insert 3, the metal tape 8 is prepared as shown in FIG. 3, and one surface of the metal tape 8 is roughened. Here, as the material of the metal tape 8, copper, silver, nickel or the like is preferably used. Also,
To roughen the surface of the metal tape 8, a blasting method in which glass beads, sand, etc. are sprayed, a roughening treatment method using a wire brush, or the like is adopted.

Next, the roughened surface is subjected to an oxidation treatment to form an oxide layer 9 to form a covering body 10. Here, in order to form the oxide layer 9, a chemical conversion treatment method using an oxidizing agent such as sodium hypochlorite, a thermal oxidation method of performing heat treatment in an oxygen stream, or the like is suitably adopted.

Then, the insert 3 is covered with the covering 10 as shown in FIG.
Then, the joint portion 11 of the covering body 10 is joined to form a composite body 12. Here, for the coating of the insert body 3 with the coating body 10, a roll homing method using a coating device 13 as shown in FIG. 5 is preferably adopted.

The coating device 13 coats the interpolating body 3 with the coating body 10 by the roll homing method. While moving the interpolating body 3, the coating body 10 obtained by surface-treating the metal tape 8 is fed out and treated. So that the surface is on the side of the interpolating body 3
The inner layer body 3 is wrapped by the roll 14 so that both sides of the cover 10 gradually approach each other by the roll 14, and the inner body 3 is covered by welding the both sides to form a composite body. Further, after that, the diameter of the composite is reduced until the coating layer on the surface of the interpolating body of the composite becomes almost incompressible. Further, the coating device 13 is provided with a seam arc torch 15 for continuously joining the joint portion 11 of the coating body 10 covering the insert body 3. The seam arc torch 15 is provided.
A diameter-reducing roll 16 is disposed behind 15. Further, in the coating device 13, the roll 14 is provided with the insert 3 and the coating 10.
Prior to feeding, the coating layer 2 of superconducting precursor powder or superconductor powder is formed on the base line 1, and a coating device 17 of precursor powder or superconductor powder for producing the insert 3 is continuously provided. , The metal tape 8 is further surface-treated to provide a covering 10
The surface treatment device 18 is connected in series. With the above-described structure of the coating device 13, the precursor powder or superconductor powder coating device 17 and the surface treatment device 18 that are connected to the coating device 13, the composite 12 is continuously formed from the base line 1 and the metal tape 8. It is formed.

Then, the composite 12 is heat-treated at a temperature of about 850 to 1000 ° C. for about 1 to 5 hours, and the coating layer 2 of the superconducting precursor powder or the superconducting powder is formed on the superconducting layer as shown in FIG.
Superconducting wire 20 is obtained as 19. In this case, in the composite 12, since the inner surface of the metal tape 8 is roughened, a minute space that acts as an air pocket is formed between the inner surface of the metal tape 8 and the insert body 3. Air remains in the space. The remaining air serves as an oxygen source when the coating layer 2 of the superconducting precursor powder or the superconducting powder is heated, and contributes to the formation of the superconducting layer 19 having a sufficient oxygen content. Further, since the oxide layer 9 is formed on the inner surface of the metal tape 8, oxygen is also supplied from the oxide layer 9 to the coating layer 2 of the superconducting precursor powder or the superconductor powder. Have a sufficient amount of oxygen.

According to such a manufacturing method, the insert body 3 on which the coating layer 2 of the superconducting precursor powder or the superconductor powder is formed is coated with the coating body 10 by roll homing, and then the composite body is covered with the surface. Since the coating layer of 1 is reduced in diameter until it becomes a state close to non-compression, the coating layer 2 of the superconducting precursor powder or superconducting powder is pressed by the coating body 10, and thus the coating of the superconducting precursor powder or the superconducting powder is performed. The cover layer 2 is sufficiently consolidated. Further, since the inner surface of the metal tape 8 is roughened and the oxide layer 9 is further formed, it is necessary to heat the coating layer 2 of the superconducting precursor powder or the superconducting powder to form the superconducting layer 19.
A sufficient amount of oxygen can be supplied.

In the method for manufacturing an oxide-based superconducting wire according to claim 2 of the present invention, the roughened surface of the metal tape 8 is oxidized in the example of the manufacturing method according to claim 1 described above. After the oxide layer 9 is formed by the above method, an oxidizer layer 21 is further formed on the surface on which the oxide layer 9 is formed, as shown in FIG. The coating is further performed, and the coating layer 2 of the inner layer body 3 is reduced in diameter until it becomes a state close to non-compression, and then heat treatment is performed to form a superconductor layer 11, and a superconducting wire 18 is obtained. Here, as the oxidizer, various metal oxides such as Bi ₂ O ₃ are used, and in order to form the oxidizer layer 19, the roughened surface of the metal tape 8 is formed in the concave portion of the oxide layer 9. It is performed by rubbing the above-mentioned oxidizing agent.

According to such a manufacturing method, the oxidant layer 21 is formed on the surface of the metal tape 8. Therefore, when the coating layer 2 of the superconducting precursor powder or the superconducting powder is heated to form the superconducting layer 19, oxidation is performed. Since a sufficient amount of oxygen can be supplied from the agent layer 21, it is possible to prevent the problem of characteristic deterioration due to lack of oxygen during firing.

[Examples] Hereinafter, the present invention will be described in more detail with reference to Examples.

(Example 1) Using the coating apparatus shown in FIG. 5, a superconducting wire provided with a Y-Ba-Cu-O-based superconductor was manufactured by the manufacturing method according to claim 1.

First, a nickel wire with an outer diameter of 2 mm is prepared, electrophoretic deposition is performed using this as a cathode, and a coating layer of superconducting precursor powder with a thickness of about 300 μm is formed on the nickel wire.
It heat-treated at 1 degreeC for 1 hour, and was set as the insert body. The electrodeposition liquid used here was a dispersion of superconducting powder in acetone. In addition, the superconducting powder, each raw material powder of CuO and Y ₂ O ₃ and _{BaCO 3 Y: Ba: Cu =} 1: 2: 3 were uniformly mixed in a molar ratio to the mixed powder, the following Then, this mixed powder is calcined in an oxygen atmosphere at 500 to 1000 ° C. for 1 to several tens of hours to obtain a calcined powder. Then, the calcined powder is subjected to a series of operations of compacting, heating, and crushing once. Alternatively, a powder having a composition of Y ₁ Ba ₂ Cu ₃ Ox prepared by repeating the process twice or more was used.

Also, a surface of a separately prepared 0.3 mm thick copper tape is roughened by blasting with glass beads, and the roughened inner surface is a hot mixture of sodium hypochlorite and sodium hydroxide. To form an oxide layer (copper oxide layer) to form a coating.

Then, the insert and the coated body are sequentially passed through a five-stage forming roll to be coated with the coated body by a roll homing method, and subsequently, a joint portion of the coated body is joined with an argon arc torch to form a composite body. Obtained. After that, the diameter of the composite was reduced until the coating layer on the surface of the insert of the composite became almost incompressible. In this state, when the thickness of the superconducting precursor layer of the insert was measured, it was confirmed that almost the whole was compressed to about 200 μm, and that the superconducting precursor layer was uniformly consolidated in the compounding process. Was done.

Then, after winding the composite, the composite was heat-treated in an electric furnace at 920 ° C. for 2 hours to form a superconductor layer, and then gradually cooled to obtain a superconducting wire.

The superconducting property of the superconducting wire thus obtained was investigated, and it was found that the critical temperature was 91 K and the critical current density at that time was 1 K.
It was 000 A / cm ² .

(Example 2) Similar to Example 1, a superconducting wire provided with a Y-Ba-Cu-O-based superconductor was manufactured by the manufacturing method according to claim 1.

First of all, prepare a copper wire, apply silver plating to it, and outer diameter 4.
The baseline was 0 mm. Next, Y ₂ O ₃ , BaCO ₃ and CuO are mixed with Y: Ba: Cu.
= 1: 2: 3 (molar ratio), and then mixed, then calcined and pulverized to produce superconducting precursor powder, and pine oil was added thereto in a weight ratio of precursor powder: pine. Oil was added so that the ratio was 8: 2 to prepare a paste. Next, the paste-like composition is applied to a base line plated with silver, and then heat-treated to decompose and eliminate the pine oil and heat-treated so that the superconducting precursor powder does not fall off due to vibrations, etc. A coating layer of superconducting precursor powder having a thickness of about 200 μm was formed.

Also, one surface of a separately prepared 0.5 mm thick copper tape was roughened with a wire brush, and the roughened surface was plated with silver having a thickness of about 2 μm. Next, this silver-plated surface was heated in an oxygen stream to form an oxide layer (silver oxide layer) to obtain a cover.

Then, the insert and the coated body are sequentially passed through a five-stage forming roll to be coated with the coated body by a roll homing method, and subsequently, a joint portion of the coated body is joined with an argon arc torch to form a composite body. Obtained. Further thereafter, the composite was compressed until the coating layer on the surface of the insert of the composite was in a nearly non-compressed state. In this state, when the thickness of the coating layer of the superconducting precursor powder of the insert was measured, it was found that almost the whole was compressed to about 130 μm, and the coating layer of the superconducting precursor powder was uniformly formed in the compounding step. It was confirmed that it was consolidated.

Then, after winding the composite, the composite was heat-treated in an electric furnace at 920 ° C. for 2 hours to form a superconductor layer, and then gradually cooled to obtain a superconducting wire.

The superconducting property of the superconducting wire thus obtained was examined, and it was found that the critical temperature was 92 K and the critical current density at that time was 2 K.
It was 300 A / cm ² .

(Comparative Example) For comparison with Examples 1 and 2 described above, the superconducting precursor layer was replaced with the superconducting precursor layer by simply heating the intercalation body at 920 ° C. for 2 hours in an oxygen atmosphere without coating with the coating body. As a superconducting wire.

When the superconducting characteristics of these superconducting wires were examined, the following values were obtained.

Comparative example with Example 1 (using a nickel wire as a baseline) Critical temperature; 83K Critical current density; 650A / cm ² Comparative example with Example 2 (using a silver-plated copper wire as a baseline) Critical temperature; 87K Critical Current density: 800 A / cm ^{2 The} critical current densities in these measured values are measured at the critical temperature of each superconductor.

"Effect of the invention" As described above, in the method for producing an oxide-based superconducting wire according to claim 1 of the present invention, the coating layer of the superconducting precursor powder or the superconducting powder is formed on the metallic base line. Then, as an interpolating body, one surface of a separately prepared metal tape is roughened, and then the roughened surface is subjected to an oxidation treatment to form a covering body,
Since the above-mentioned interpolating body is coated with the coating so that the oxidized surface of the coating is on the inside to form a composite, and then the composite is subjected to heat treatment to form a superconducting wire. , By coating the intercalation body with a coating, it is possible to pressurize the coating layer of the superconducting precursor powder or the superconducting powder to consolidate the coating layer of the superconducting precursor powder or the superconducting powder, A superconducting wire having excellent superconducting properties can be produced. Further, by making the inner surface of the metal tape rough and allowing air to remain in a minute space on the rough surface, and by forming an oxide layer on the rough surface and using the oxide layer as a source of oxygen, the superconductivity can be improved. When forming the sintered layer of the superconductor from the coating layer of the precursor powder or the superconductor powder, it is possible to supply a sufficient amount of oxygen, thus preventing deterioration of the characteristics of the superconducting wire due to lack of oxygen. be able to.

Further, in the production method according to claim 2 of the present invention, a coating layer of superconducting precursor powder or superconducting powder is formed on a metal base line to form an intercalation body, and one surface of a separately prepared metal tape Is roughened, and then the roughened surface is subjected to an oxidation treatment, and an oxidizing agent layer is further formed on the oxidized surface to form a covering body. The coated body was coated with the coating so that the formed surface faces the inside, and then the composite was subjected to heat treatment to obtain a superconducting wire. Therefore, the superconducting precursor powder or the superconducting powder was applied. When the covering layer is heated and sintered to form the superconducting layer, sufficient oxygen is supplied from the oxidizer layer during firing, so the superconducting characteristics with a high critical temperature even for thick coating layers. It is possible to obtain an excellent sintered layer of From being densified in the tape coating step, sintering time is extremely small porosity sintered body is obtained, it is possible to obtain an excellent superconducting wire in the critical temperature and critical current density.

[Brief description of drawings]

1 to 5 are views relating to a method for manufacturing an oxide-based superconducting wire according to the present invention. FIG. 1 is a cross-sectional view of an interpolating body, and FIG. FIG. 3 is a side sectional view showing a metal tape in a state in which a surface is roughened and an oxide layer is further formed, and FIG. 4 is a step of forming a composite body by covering an insert body with a cover body. FIG. 5 is a schematic configuration diagram of a coating apparatus suitably used in the manufacturing method of the present invention, and FIG. 6 is a schematic configuration diagram of the obtained superconducting wire. 1 ... Base line, 2 ... Coating layer of superconducting precursor powder or superconducting powder, 3 ... Intercalation body, 8 ... Metal tape, 9 ... Oxidation layer, 10 ... Coating body, 12 ... Composite Body, 13 ... coating device, 19 ... superconductor layer, 20 ... superconducting wire, 21 ... oxidizer layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Satoru Kono 1-5-1, Kiba, Koto-ku, Tokyo Fujikura Electric Cable Co., Ltd. (72) Yoshimitsu Ikeno 1-1-5, Kiba, Koto-ku, Tokyo Fujikura Electric Cable Incorporated (72) Inventor Tadayuki Nokata 1-5-1, Kiba, Koto-ku, Tokyo Fujikura Electric Cable Co., Ltd. (72) Inventor Mikio Nakagawa 1-1-5, Kiba, Koto-ku, Tokyo Fujikura Electric Cable Co., Ltd. (72) Inventor Yu Sugimoto 1-5-1, Kiba, Koto-ku, Tokyo Within Fujikura Electric Cable Co., Ltd.

Claims (2)

(57) [Claims] 1. A superconducting precursor powder or superconducting powder is coated on a metallic base line, and the coating layer is heat treated at a high temperature to form an intercalating body, and one surface of the metal tape is roughened. Then, the roughened surface is oxidized to form a coating, and the interpolated body is coated with the coating so that the oxidized surface of the coating is the inside to form a composite, Thereafter, a heat treatment is applied to this composite, which is a method for producing an oxide-based superconducting wire. 2. A metal base line is coated with a superconducting precursor powder or a superconductor powder, and the coating layer is heat treated at a high temperature to form an intercalation body, and one surface of the metal tape is roughened. Next, the roughened surface is subjected to an oxidation treatment, and an oxidant layer is further formed on the oxidized surface to form a coating, and the interpolated body is a surface on which the oxidant layer of the coating is formed. A method for producing an oxide-based superconducting wire, which comprises coating the inside of the composite with the coating to form a composite, and then subjecting the composite to a heat treatment.