JPH06251929A - Manufacture of oxide superconducting coil - Google Patents

Abstract

PURPOSE:To obtain an oxide superconducting coil having a highly generated magnetic field by a method wherein an insulative film and a normal conductive metal layer are formed on an oxide wire material, which is turned into a superconductor by a heat treatment, by an oxidation and thereafter, the wire material is molded into a coil form and this coil is subjected to heat treatment and oxidation treatment. CONSTITUTION:Raw powders, which consist of oxides of a Bi2O3 and a CuO and carbonates of SrCO3 and CaCO3, which are blended in such a way that oxide powder is blended in a compositional ratio of Bi2Sr2Ca1Cu2O8 when the raw powders are subjected to heat treatment and are formed into the oxide powder, are mixed with one another and thereafter, the mixture is calcined in the air. Then, a load is applied to this oxide powder by an oil pressure press to form a cylindrical pellet, and this pellet is inserted in an Ag pipe and moreover, is inserted in an Nb pipe to form a composite material 3 consisting of oxides 1-Ag and 2-Nb. A wire material obtained by processing this composite material is wound into a solenoid form to form a coil and this coil is subjected to heat treatment in the air to obtain an oxide superconducting coil. Thereby, it becomes possible to manufacture an oxide superconducting coil having a highly generated magnetic field.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an oxide superconducting coil which generates a high magnetic field.

[0002]

2. Description of the Related Art Recently, high energy physics, magnetic levitation trains,
In fields such as nuclear magnetic resonance apparatus and basic physical property research, there is an increasing need for superconducting coils and magnetic shield materials with low operating costs. The conventional superconducting coil is made of an alloy having a low critical temperature or a superconducting wire made of an intermetallic compound superconductor. In 1987, an oxide superconductor with a very high critical temperature was discovered, which showed superconductivity even at liquid nitrogen temperature (77K). This oxide superconductor is, for example, (Bi _1-X Pb _X ) Sr _Y Ca _Z
It is an oxide represented by the composition of Cu _W O _P. Here, X is 0 to 0.4, Y, Z, and W are 0.5 to 2. This is usually Bi ₂ O ₃ , PbO, CuO, SrCO ₃ , CaC
It is produced by mixing each powder of O ₃ and heat-treating after molding. Regarding the manufacturing technology in this field, for example, publications {J. J. A. P. , 27 (1988) L1041}. That is, the conventional oxide superconducting wire having a high critical temperature is Bi-Pb-Sr-Ca-Cu.
Taking an example of an —O-based oxide, Bi ₂ O ₃ , PbO, SrC
Each powder of O ₃ , CaCO ₃ , and CuO is mixed, calcined and shaped, inserted into a metal pipe, processed into a wire, and then heat-treated. Further, the coil is manufactured by winding it in a pancake shape while sandwiching an insulating tape or sheet of alumina or the like, and the insulating tape or sheet is braided with alumina fiber or the like so as to withstand bending stress during coil winding. It is common to use a flexible one.

[0003]

In the oxide superconducting wire produced by the above-mentioned conventional method, in order to improve the magnetic field generated by the coil, the thickness of the insulating tape is reduced so that the superconductor per cross section of the coil is reduced. It is necessary to increase the space factor, but due to the hardness of the alumina fiber or the like, it is difficult to braid a thin insulating layer in a tape or sheet shape with the alumina fiber, and therefore the magnetic field generated by the coil is low.

The present invention has been made to solve the above problems, and an object thereof is to obtain a method for manufacturing an oxide superconducting coil having a high magnetic field generated.

[0005]

A method of manufacturing an oxide superconducting coil according to the present invention comprises a step of forming a normal conducting metal layer which becomes insulative by oxidation on an oxide wire which becomes a superconductor by heat treatment, and has a coil shape. This is a method of performing a forming step, a heat treatment to obtain a superconductor, and an oxidation treatment step.

Further, the normal conducting metal layer which becomes insulating by oxidation is provided by forming a layer containing a normal conducting metal powder which becomes insulating by oxidation.

Further, a normal conductive metal layer which becomes insulating by oxidation is provided by vapor deposition of a normal conductive metal which becomes insulating by oxidation.

[0008]

Since the method of the present invention is used, the thickness of the normal-conducting metal layer can be made less than 0.1 mm, and the insulating layer occupying the coil cross section is 50% or less, which is very small compared with the conventional one, so that the high generation rate is high. An oxide superconducting coil having a magnetic field is obtained.

[0009]

【Example】

Example 1. When heat treated to form an oxide, Bi ₂ Sr ₂
Bi formulated to have a composition ratio of Ca ₁ Cu ₂ O _8
2 O ₃ , CuO oxide, SrCO ₃ , CaCO ₃ carbonate raw material powder (purity 99.99%, average particle size ~ 5 μm) were mixed well and then in air at 700 to 850 ° C for 10 to 60 hours. It was calcined in. A length of 50 m is obtained by applying a load of about 1000 kg / cm ² to the oxide powder with a hydraulic press.
A cylindrical pellet having a diameter of m and a diameter of 5.8 mm was produced. The pellets obtained in this way were put into an Ag pipe (φ9mm × φ6m
m), and further Nb pipe (φ11.5mm × φ
9.5 mm) to obtain an oxide-Ag-Nb composite. The composite is swaged and drawn to a diameter of 1
A wire having a diameter of 0.8 mm (a diameter of 0.8 mm not including Nb) was obtained.
Further, the obtained wire was wound in a solenoid shape to manufacture a coil having a diameter of 80 mm as shown in FIG. Note that FIG.
FIG. 3 is a configuration diagram of a coil before an oxidation heat treatment according to an embodiment of the present invention, in which 1 is an oxide, 2 is Ag, and 3 is Nb of a normal-conducting metal layer. Next, the coil is placed in air for 8
Heat treatment was performed at 00 to 900 ° C. for 10 to 120 hours to obtain an oxide superconducting coil according to an example of the present invention. The insulation resistance between the wire rods of this coil was sufficiently high. Table 1 shows the magnetic field generated by this coil in a magnetic field of 4.2 K, and Table 2 shows the number of turns of the wire and the area ratio of the oxide superconductor to the coil cross-sectional area.

[0010]

[Table 1]

[0011]

[Table 2]

Comparative Example 1. Oxide and Ag in Example 1
A pipe composite having a diameter of 0.8 mm is produced by swaging, drawing and rolling a pipe composite, and a conventionally used alumina fiber (80% Al ₂ O ₃ -20% SiO ₂ ) is braided (bag knitting) into the wire. Then, it was wound in the form of a solenoid, and a coil was produced in the same manner as in Example 1. The insulation resistance between the wire rods of this coil was sufficiently high. The measurement results similar to those in Example 1 are shown in Tables 1 and 2.

The coil obtained in Example 1 has a smaller area of insulating material in the coil cross-sectional area than the coil using alumina fiber conventionally used as the insulating material in Comparative Example 1. It was possible to obtain a high generated magnetic field.

Example 2. When the oxide is _{heat-treated, Bi 1.6 Pb 0.4 Sr 2 Ca} 2 Cu 2 O 8 Bi 2 O 3 were blended so that the composition ratio of, PbO, oxides of CuO, SrCO _3, CaCO ₃ Raw powder of carbonate (purity 9
9.99%, average particle size ~ 5 μm) were mixed well and then
It was calcined in air at 00 to 850 ° C for 10 to 60 hours. About 1000 Kg / c of this oxide powder is obtained by a hydraulic press.
By applying a load of m ² , a cylindrical pellet having a length of 50 mm and a diameter of 5.8 mm was prepared. The pellets thus obtained were inserted into an Ag pipe (φ9 mm × φ6 mm), and drawn and rolled to obtain a tape having a width of 4.5 mm and a thickness of 0.18 mm. Furthermore, a metal Nb tape having a thickness of 0.05 mm was sandwiched and wound in a pancake shape to prepare a coil having a diameter of 100 mm as shown in FIG. In addition, in FIG.
It is a block diagram of the coil before the oxidation heat processing concerning the other Example of this invention. Next, the coil is placed in the air at 800 to 90
Heat treatment was performed at 0 ° C. for 10 to 120 hours to obtain an oxide superconducting coil according to another embodiment of the present invention. Table 1 shows the magnetic field generated by this coil at 77K in a magnetic field, and Table 2 shows the number of turns of the tape and the area ratio of the oxide superconductor to the coil cross-sectional area.

Comparative Example 2. In Example 2, instead of the Nb tape, the alumina fiber (80
% Al ₂ O ₃ -20% SiO ₂ ). A coil similar to that of Example 2 was produced in the same manner as in Example 2 except that a tape braided with (Al ₂ O ₃ -20% SiO ₂ ) was sandwiched and wound in a pancake shape. The measurement results similar to those in Example 2 are shown in Tables 1 and 2.

The coil obtained in Example 2 has a smaller area of the insulating material in the coil cross-sectional area than the coil using alumina fiber conventionally used as the insulating material in Comparative Example 2. It was possible to obtain a high generated magnetic field.

Embodiment 3. Bi ₂ O ₃ , PbO, CuO oxides, S, which were compounded so as to have a composition ratio of Bi _1.6 Pb _0.4 Sr ₂ Ca ₂ Cu ₂ O ₈ when heat treated to form oxides.
Raw material powder of rCO ₃ and CaCO ₃ carbonate (purity 99.9
9%, average particle size ~ 5 μm) and then 700 ~
It was calcined in air at 850 ° C. for 10 to 60 hours. A load of about 1000 kg / cm ² was applied to the oxide powder by a hydraulic press to form a cylindrical pellet having a length of 50 mm and a diameter of 5.8 mm. The pellets thus obtained are Ag
The tape having a width of 4.5 mm and a thickness of 0.18 mm was obtained by inserting it into a pipe (φ9 mm × φ6 mm) and drawing and rolling it. Next, a metal tantalum powder having a particle diameter of 3 μm was dissolved in alcohol and applied on the surface of the Ag tape and wound in a pancake shape to prepare a coil having a diameter of 100 mm as shown in FIG. 3 is a block diagram of a coil before oxidation heat treatment according to another embodiment of the present invention, in which 3 is a Ta powder coated surface of the normal conducting metal layer. Next, the coil was heat-treated in air at 800 to 900 ° C. for 10 to 120 hours to obtain an oxide superconducting coil according to another example of the present invention. Table 1 shows the magnetic field generated by this coil at 77K in a magnetic field, and Table 2 shows the number of turns of the tape and the area ratio of the oxide superconductor to the coil cross-sectional area.

In the coil according to the third embodiment, the area of the insulating material in the coil cross-sectional area can be reduced as compared with the comparative example 2 in which the conventional alumina fiber tape is used as the insulating material, so that a high generated magnetic field can be obtained. It was

Example 4. Raw powder of Y ₂ O ₃ , CuO oxide, and BaCO ₃ carbonate compounded so that the composition ratio of YBa ₂ Cu ₃ O _6.5 when heat-treated into oxide (purity 99.99%, average (A particle size of ˜5 μm) was thoroughly mixed and then fired in air at 700 to 950 ° C. for 10 to 60 hours. Ethanol was added to this oxide powder, and the paste was applied to an Ag tape, which was then heated to 800-
After heat treatment at 1000 ° C. for 10 to 120 hours, Ag was vapor-deposited by about 10 μm on the paste applied by the CVD method, and Nb was vapor-deposited by about 50 μm on the paste. The obtained tape was wound into a pancake shape to prepare a coil having a diameter of 100 mm as shown in FIG. 4 is a block diagram of a coil before oxidation heat treatment according to another embodiment of the present invention, in which 3 is Nb of the normal conducting metal layer.
It is a powder coated surface. Next, the coil is placed in the air at 800
Heat treatment was performed at ˜1000 ° C. for 10 to 120 hours to obtain an oxide superconducting coil according to another embodiment of the present invention. Table 1 shows the magnetic field generated in the 77K magnetic field of this coil, and Table 2 shows the number of turns of the tape and the area ratio of the oxide superconductor to the coil cross-sectional area.

The coil according to Example 4 was able to obtain a high generated magnetic field as a result of being able to reduce the area of the insulating material in the coil cross-sectional area as compared with the coil D using the conventional alumina fiber tape as the insulating material. .

In the above embodiment, Bi-Sr-Ca-
Cu-O, Bi-Pb-Sr-Ca-Cu-O, Y-B
Although the a-Cu-O-based oxide has been described, other superconductive oxides having a high critical temperature, such as Tl-B, are used.
Although it may be applied to a-Ca-Cu-O oxide, and Nb and Ta have been described as the normal-conducting metals, other ones can be used as long as they can be formed on a wire and exhibit an insulating property by oxidation. But it can be used. Further, in the above embodiment, the heat treatment is carried out in air at 800 to 1000 ° C. for 10 to 12
It was performed for 0 hours, but the oxygen in the heat treatment atmosphere was changed from 1% to 100
%, The heat treatment temperature range is not necessarily limited to this temperature range, and a high generated magnetic field can be obtained at 700 to 1000 ° C. In the above example, an oxide wire that becomes a superconductor by heat treatment is used,
The case where the superconducting metal layer is oxidized and the oxide wire is heat-treated at the same time to form the insulating layer by oxidizing the superconductor and the normal conducting metal is shown.However, the superconductor and the insulating layer are generated separately. Obviously, in the case of the oxide superconducting wire, it is clear that it is sufficient to form the insulating layer by oxidation without heat treatment.

[0022]

As described above, according to the present invention, a step of forming a normal conductive metal layer which becomes insulative by oxidation on an oxide wire which becomes a superconductor by heat treatment, a step of forming into a coil shape, and a heat treatment. By performing the step of obtaining the superconductor and the step of performing the oxidation treatment, it is possible to obtain a method for manufacturing an oxide superconducting coil having a high generated magnetic field. Further, by providing a normal conductive metal layer that becomes insulative by oxidation, by forming a layer containing a normal conductive metal powder that becomes insulative by oxidation, or by depositing a normal conductive metal that becomes insulative by oxidation. Can be provided.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a coil before an oxidation heat treatment according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a coil before an oxidation heat treatment according to another embodiment of the present invention.

FIG. 3 is a configuration diagram of a coil before an oxidation heat treatment according to another embodiment of the present invention.

FIG. 4 is a configuration diagram of a coil before an oxidation heat treatment according to still another embodiment of the present invention.

[Explanation of symbols]

 1 Oxide 3 Normal conductive metal layer

Claims (3)

[Claims] 1. A step of forming a normal conducting metal layer which becomes insulating by oxidation on an oxide wire which becomes a superconductor by heat treatment, a step of forming into a coil shape, a step of heat treatment to obtain a superconductor, and an oxidation treatment. A method of manufacturing an oxide superconducting coil, which comprises the step of: 2. The method according to claim 1, wherein the normal conductive metal layer which becomes insulating by oxidation is provided by forming a layer containing a normal conductive metal powder which becomes insulating by oxidation. And a method for manufacturing an oxide superconducting coil. 3. The oxide superconducting material according to claim 1, wherein the normally conducting metal layer which becomes insulative by oxidation is provided by depositing a normally conducting metal which becomes insulative by oxidation. Coil manufacturing method.