JP2549697B2 - 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-based superconductors having a critical temperature (Tc) at which a transition from a normal conducting state to a superconducting state has a value equal to or higher than the temperature of liquid nitrogen have been discovered. This type of oxide-based superconductor has the general formula AB-Cu-O (where A is La, Ce, Y).
b, Sc, Er, etc., Group IIIa element of the Periodic Table and one or more members of Group Vb of the Periodic Table, Bi, Sb, etc., and B is a Group IIa element of the Periodic Table, such as Ba, Sr. 1 or more types of) are shown). 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 A method of obtaining a superconducting wire by obtaining a superconducting wire by subjecting each of the elements of the powder compact inside to a solid phase reaction by subjecting the wire to a linear wire of There is.

[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, and 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 manufactured.

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 density 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. It is heat-treated at a high temperature so as not to come off or fall into powder to form an insert, and the inner surface of the metal pipe having an inner diameter approximately the same as the outer diameter of this insert is roughened, and then this roughened inner surface Is oxidized, and then the metal pipe is heated and expanded, and in this state, the insert is inserted to form a composite, and the composite is once cooled, and then the composite is heat-treated to form a superconducting wire. This is the means for solving the above problems.

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. Is heat treated to form an interpolating body, the inner surface of a metal pipe having an inner diameter of approximately the same length as the outer diameter of the interpolating body is roughened, then the roughened inner surface is subjected to an oxidation treatment, and then this An oxidant layer is formed on the inner surface subjected to the oxidation treatment, and then the metal pipe is heated and expanded, and in this state, the insert is inserted to form a composite, and the composite is cooled once, and then the composite is formed. Heat treatment to form a superconducting wire was used as a means for solving 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, a superconducting precursor powder or a superconducting powder is coated on a metallic base line 1 and then heat-treated at a high temperature so that the coating layer does not peel off or fall off due to vibration or the like. The cover layer 2 is formed to produce the insert body 3.
Here, the base line 1 may be solid or hollow (a solid one is shown in FIG. 1), and its material is copper, silver, nickel, tungsten, zirconium, titanium, etc. Is preferably used. The coating covering layer 2 of the method for forming a superconductor precursor or a superconductor, such as mixed case of manufacturing a Y-Ba-CuO-based superconductor, Y ₂ O _3, BaCO _3, the CuO powder at a predetermined ratio S 500
Heat-treatment at ~ 1000 ° C to form a calcined body, then pulverize it to obtain a superconducting precursor or heat-treat at 500-1000 ° C to obtain a superconductor powder, and use this for electrophoretic deposition. The coating layer 2 is formed on the base line 1 by various methods described above, and then heat-treated at a high temperature so that the coating layer 2 does not fall off or fall off due to vibration or the like to form the coating layer 2 of the superconducting precursor or the superconductor. In order to form the superconducting precursor or superconductor coating layer 2 on the base line 1 by the electrophoretic deposition method, first, the base line 1 is immersed in the electrodeposition solution 5 in the electrodeposition tank 4 as shown in FIG. This serves as a cathode, and a DC voltage is applied between this and the anode 6. Here, either the constant voltage method or the constant current method may be adopted as the electrodeposition operation.
When a DC voltage of V or more is applied and the constant current method is adopted, the current density should be in the range of 0.05 to 5 mA / cm ² . Also,
As the electrodeposition liquid 5, an oxide superconductor powder or a precursor powder of the oxide superconductor 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). Periodic table Vb
And B represents one or more elements of Group IIa of the periodic table such as Ba and Sr. ).
The composition of each constituent element of the oxide superconductor is, for example, Y: Ba: Cu: O = 1: 2: 3: (7
−δ), and δ is in the range of 0 ≦ δ ≦ 5. As the superconductor powder, a powder having a particle size of about 0.1 to 50 μm is used, and a fine powder of about 0.1 to 5 μm is particularly 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 The calcinated powder is subjected to a series of operations of compacting → heating → crushing once or twice or more to obtain a superconducting powder having a composition of Y ₁ Ba ₂ Cu ₃ Ox. 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.

Further, as the precursor powder of the oxide-based superconductor,
The above-mentioned calcined powder which is an intermediate substance for obtaining a superconductor powder is used.

Further, although acetone is preferably used as the dispersion medium, other organic solvents such as an acetone thread 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 carried out for 1 hour, the coating layer 2 of the superconducting precursor or the superconducting powder which is dense and uniform as a whole without uneven thickness on the surface is formed.

Separately from the production of the inner insert 3, a metal pipe 8 having an inner diameter substantially the same as the outer diameter of the meat insert 3 is prepared as shown in FIG. Roughen the inner surface. Here, as the material of the metal pipe 8, copper, silver,
Metals such as nickel, zirconium and titanium are preferably used. Further, in order to roughen the inner surface of the metal pipe 8,
A roughening treatment method such as a blasting method in which glass beads or sand is blown is preferably adopted.

Next, the roughened inner surface is subjected to an oxidation treatment to form an oxide layer 9 as shown in FIGS. 3 and 4. 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 metal pipe 8 is heated and expanded, and in this state, the insert 3 is inserted, so-called shrink fit is performed to form a composite 10 as a whole as shown in FIG. Cool 10 once. Then, in this composite body 10, the insert body 3 is easily inserted by the thermal expansion of the metal pipe 8 and the entire body is cooled, so that the coating layer of the superconductor precursor powder or the superconductor powder of the insert body 3 is coated. Two
Are pressed against the inner surface of the metal pipe 8 to be sufficiently consolidated.

Then, the composite 10 is subjected to 1 at a temperature of about 850 to 1000 ° C.
A heat treatment is performed for about 5 hours to obtain a superconducting wire 12 by using the coating layer 2 of the superconducting precursor powder or the superconducting powder as the superconductor layer 11. In this case, in the composite body 10, since the inner surface of the metal pipe 8 is roughened, a minute space acting as an air pocket is formed between the inner surface of the metal pipe 8 and the insert body 3. Air remains in the space. Then, this residual air serves as an oxygen source when the coating layer 2 of the above-mentioned superconducting precursor powder or superconducting powder is heated, and contributes to the formation of the superconducting layer 11 having a sufficient oxygen content. Also,
Since the oxide layer 9 is formed on the inner surface of the metal pipe 8, oxygen is also supplied from the oxide layer 9 to the coating layer 2 of the superconducting precursor powder or the superconductor powder. Will have a quantity.

According to such a manufacturing method, the insert 3 having the coating layer 2 of the superconducting precursor powder or the superconducting powder formed thereon is inserted into the metal pipe 8 by shrink fitting, so that the metal pipe 8 is cooled when it is cooled. 8 is contracted to press the coating layer 2 of the superconducting precursor powder or the superconductor powder, and thus the coating layer 2 of the superconducting precursor powder or the superconductor powder is sufficiently consolidated. Further, since the inner surface of the metal pipe 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 11 in a sufficient amount. Oxygen can be supplied.

In the method for manufacturing an oxygen-based superconducting wire according to claim 2 of the present invention, the roughened inner surface of the metal pipe 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 process, an oxidizer layer 13 is further formed on the inner surface on which the oxide layer 9 is formed, as shown in FIG. Heat treatment is performed to form a superconductor layer 11 to obtain a superconducting wire 12. Here, various metal oxides such as Bi ₂ O ₃ are used as the oxidant, and in order to further form the oxidant layer 11,
This is performed by rubbing the above-mentioned oxidizing agent into the concave portion of the oxide layer 9 on the inner surface of the roughened metal pipe 8.

According to such a manufacturing method, since the oxidizer layer 13 is formed on the inner surface of the metal pipe 8, when the coating layer 2 of the superconducting precursor powder or the superconducting powder is heated to form the superconducting layer 11, oxidation is performed. It is possible to supply a sufficient amount of oxygen from the agent layer 13, and thus it is possible to prevent a shortage of oxygen in the obtained superconductor.

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

(Example 1) By the manufacturing method according to claim 1, a superconducting wire including a Y-Ba-Cu-O-based superconductor was produced.

First, prepare a nickel wire with an outer diameter of 2 mm, perform electrophoretic deposition using this as a cathode, and form a coating layer of superconducting precursor powder with a thickness of about 200 μm on the nickel wire.
It heat-processed at 0 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.

In addition, a copper pipe with an outer diameter of 4.3 mm and an inner diameter of 2.40 to 2.45 mm prepared separately is roughened by blasting with glass beads, and the roughened inner surface is treated with sodium hypochlorite and hydroxide. It was oxidized by a chemical conversion treatment with a mixed solution with sodium. This copper pipe is then
It was heated and expanded to 2.50 mm, and in this state, the above-mentioned insert body was quickly inserted to obtain a composite body. Further, after air-cooling the composite to normal temperature, the thickness of the superconducting precursor coating layer of the inserted insertion body was measured, and almost 100
It was confirmed that the superconducting precursor coating layer was uniformly compacted by the shrink fitting operation.

Then, the composite was heat-treated in an electric furnace at 900 ° C. for 3 hours to form a superconductor layer and then gradually cooled to obtain a superconducting wire.

When the superconducting properties of the superconducting wire thus obtained were investigated, the critical temperature was 90 K and the critical current density at that time was 1
It was 500 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, a copper wire was prepared and plated with nickel to form a base wire having an outer diameter of 2.0 mm. Next, using this base line as a cathode, electrophoretic electrodeposition was performed in the same manner as in Example 1 described above, and a precursor coating of a Y-Ba-Cu-O-based supermotor body having a thickness of about 300 μm was applied on the base line. Layers were formed to give an insert.

In addition, a separately prepared silver pipe with an outer diameter of 3.3 mm and an inner diameter of 2.5 mm is roughened by blasting the inner surface, and the roughened inner surface is heated and oxidized in an oxygen stream to be oxidized to a sufficient thickness. A silver (Ag ₂ O) layer was formed.

Next, this silver pipe was heated and expanded until its inner diameter became 2.7 mm, and in this state, the above-mentioned insert body was quickly inserted to obtain a composite body. Furthermore, after air-cooling this composite to normal temperature, the thickness of the superconducting precursor coating layer of the inserted insertion body was measured, and almost the whole was compressed to about 230 μm, similar to the previous example. It was confirmed that the superconducting precursor coating layer was uniformly consolidated by the shrink fitting operation.

Then, the above composite was heat-treated in an electric furnace at 900 ° C. for 3 hours to form a superconducting layer, and then gradually superposed to obtain a superconducting wire.

When the superconducting properties of the superconducting wire thus obtained were investigated, the critical temperature was 92 K and the critical current density at that time was 1 K.
It was 900 A / cm ² .

(Example 3) By the manufacturing method according to claim 2, a superconducting wire including a Y-Ba-Cu-O-based superconductor was produced.

First, a tungsten wire having an outer diameter of 2 mm was prepared, and using this as a cathode, electrophoretic deposition was performed in the same manner as in Example 1 described above,
Y-Ba-Cu-O with a thickness of about 300 μm on a tungsten wire
A precursor coating layer for the superconducting superconductor is formed.
It heat-treated at 1 degreeC for 1 hour, and was set as the insert body.

In addition, the inner surface of a separately prepared nickel pipe with an outer diameter of 3.5 mm and an inner diameter of 2.5 mm is roughened by blasting, and the roughened inner surface is heated and oxidized in an oxygen stream to be oxidized to a sufficient thickness. A nickel layer was formed.

Then, BiO ₂ O ₃ fine powder as an oxidant was applied to the concave portion of the rough surface on which the nickel oxide layer was formed to form an oxidant layer.

Then, this copper pipe was heated and expanded until its inner diameter became 2.7 mm, and in this state, the above-mentioned insert body was quickly inserted to obtain a composite body. Furthermore, after cooling this composite body to room temperature by air cooling, the thickness of the superconducting precursor layer of the inserted insert was measured, and it was found that almost the whole was compressed to about 220 μm, and the superconducting precursor was compressed by the shrink fitting operation. It was confirmed that the body covering layer was uniformly consolidated.

Then, the composite was heat-treated in an electric furnace at 900 ° C. for 3 hours to form a superconductor layer, and then gradually cooled to obtain a superconducting wire.

When the superconducting properties of the superconducting wire obtained in this way were examined, the critical temperature was 90 K and the critical current density at that time was 2 K.
It was 500 A / cm ² .

(Comparative Example) For comparison with Examples 1 to 3 described above, the shrinkage fitting operation was not performed, and the insert was simply heated in an oxygen atmosphere at 920 ° C. for 2 hours to convert the superconducting precursor layer into a superconducting layer. 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; 700A / cm ² Comparative example with Example 2 (using a nickel-plated copper wire as a baseline) Critical temperature; 80K critical Current density: 500A / cm ² Comparative example with Example 3 (Tungsten wire is used as a baseline) Critical temperature; 82K Critical current density; 650A / cm ^{2 In} these measured values, the critical current densities are the respective superconductors. It was measured at the critical temperature of.

"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. To form an interpolated body, the inner surface of a metal pipe having an inner diameter of approximately the same length as the outer diameter of the interpolated body is roughened, the roughened inner surface is then subjected to an oxidation treatment, and then the metal pipe Is heat-expanded, and in this state the above-mentioned intercalation body is inserted to form a composite body, and after this composite body is once cooled, the composite body is heat-treated to form a superconducting wire. By inserting the insert having the coating layer of the powder or superconductor powder into the metal pipe by so-called shrink fitting, the metal pipe is stored during cooling and the coating layer of the superconducting precursor powder or superconductor powder is formed. Press the superconducting precursor powder or superconducting The coating layer of the conductor powder can be sufficiently compacted, and thus a superconducting wire having excellent superconducting properties can be produced. Also, roughen the inner surface of the metal pipe,
Covering the superconducting precursor powder or the superconducting powder by leaving air in a minute space on the rough surface and forming an oxide layer on the rough surface and using the oxide layer as a source of oxygen. When the layer is fired to form a sintered superconductor layer, a sufficient amount of oxygen can be supplied, so that deterioration of the characteristics of the superconducting wire due to lack of oxygen can be prevented.

Further, in the method for manufacturing an oxide-based superconducting wire according to claim 2 of the present invention, in the manufacturing method according to claim 1 described above, the roughened inner surface of the metal pipe is subjected to an oxidation treatment to form an oxide layer. After forming the oxide layer, an oxidant layer was formed on the inner surface on which the oxide layer was further formed, and then shrink-fitted, cooled once, and further heat-treated to form a superconductor layer to obtain a superconducting wire. By forming the oxidant layer, when forming a superconductor layer by heating and sintering the coating layer of the superconducting precursor powder or superconductor powder, oxygen can be supplied from the oxidant layer, It is possible to obtain a superconducting wire having excellent superconducting properties without deterioration in properties due to lack of oxygen during firing.

[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. 3 and 4 are schematic views for showing a metal pipe in a state where a roughened surface and an oxide layer are further formed. FIG. 3 is a cross-sectional view and FIG. 4 is a side sectional view. FIG. 5 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 pipe, 9 ... Oxidation layer, 10 ... Composite, 11 ... Superconductivity Body layer, 12 ... Superconducting wire, 13 ... Oxidizing agent layer.

Continued front page (72) Inventor Sakuno 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 Co., Ltd. (72) Nobuyuki Katakata, 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, Inc. (72) Inventor Yu Sugimoto 1-5-1, Kiba, Koto-ku, Tokyo Fujikura Electric Cable Co., Ltd.

Claims (2)

(57) [Claims] 1. A metal base line is coated with a superconducting precursor powder or a superconductor powder and then heat-treated at a high temperature to obtain an interpolating body, and an inner diameter of a length substantially the same as the outer diameter of the interpolating body. The inner surface of the metal pipe is roughened, the roughened inner surface is then subjected to an oxidation treatment, and then the metal pipe is expanded by heating. In this state, the insert is inserted into a composite, and the composite A method for producing an oxide-based superconducting wire, which comprises heat-treating the composite after once cooling the body. 2. A metallic base line is coated with superconducting precursor powder or superconducting powder and then heat-treated at high temperature to obtain an interpolating body, and an inner diameter having a length substantially the same as the outer diameter of the interpolating body. Roughening the inner surface of the metal pipe having, then oxidizing the roughened inner surface, then forming an oxidant layer on the oxidized inner surface, and then subjecting the metal pipe to heat expansion, A method for producing an oxide-based superconducting wire, which comprises inserting an intercalating body to form a composite, further cooling the composite once, and then heat-treating the composite.