JP2621270B2 - Superconducting material for magnetic shield - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a magnetic shielding material, and more particularly to a superconducting material for magnetic shielding using a ceramic-based superconducting material.

(Prior art) Magnetic shielding materials are used to protect various electrical devices from induction disturbances from external magnetic fields. As such shielding materials, there are known metal plates and paints mixed with metal powder. Have been. However, such a magnetic shielding material has an electrical resistance and is effective at high frequencies, but cannot shield a static magnetic field or a slowly changing magnetic field. Because of its small size, it is difficult to shield the entire device, while the latter has a drawback that it is not enough to shield against a strong magnetic field, particularly a superconducting magnet or the like, which is a source of the strong magnetic field.

The present applicant previously filed an application for a method using a compound-based Nb ₃ Sn superconducting material as a method for manufacturing a superconducting plate for magnetic shielding that can be used to reduce the magnetic field strength in the passenger compartment of a maglev train, for example ( JP-A-59-180109, Japanese Patent Application Sho
No. 60-258373). These shields use superconducting material, so their magnetic shielding effect is large,
Since a rolled material obtained by laminating an Nb plate and a Cu plate is used, the flexibility is poor and there is a limit in using the material as a shielding material.

In recent years, the development of ceramic superconducting materials has been proceeding at a remarkable speed, and over the current year, materials exhibiting a critical temperature of 233K or higher than room temperature have been reported. Such materials could be used at liquid nitrogen temperature or room temperature, technical,
It has the advantage that is economically very advantageous having but drawbacks on hard compared to the superconducting material of the conventional alloy system (Nb-Ti alloy) or a compound based (Nb ₃ Sn, etc.), and brittle.

The present invention relates to a magnetic shielding material using such a ceramic-based superconducting material, and also overcomes the above-mentioned disadvantages of the magnetic shielding plate using Nb ₃ Sn.

(Problems to be Solved by the Invention) The present invention has the drawbacks of the above-mentioned conventional magnetic shielding material, namely, low flexibility, large weight, low shielding efficiency against a static magnetic field or a slowly changing magnetic field, superconductivity. The present invention solves all problems such as insufficient shielding of a strong magnetic field such as a magnet.

Several methods of manufacturing wires using ceramic superconducting materials have been published so far. When manufacturing a sheet using such a method, it is necessary to (a) heat the amorphous tape in an oxygen atmosphere. (B) It is conceivable that the ceramic powder is housed in a metal tube or the like, subjected to rolling or the like, and formed into a tape shape. However, the method (a) requires extremely rapid cooling and is difficult to handle as a shielding material, and the method (b) has difficulty in supplying oxygen to the inside after molding, so that the superconducting properties Is difficult to produce, and it is difficult to produce a wide or long sheet, and both have the disadvantage that the production process is complicated. The present invention also solves such difficulties.

[Structure of the Invention] (Means for Solving the Problems) The superconducting material for a magnetic shield of the present invention is provided with a sintered layer made of a ceramic superconducting material on one or both sides of a flexible ceramic planar body. A superconducting stabilizing layer made of one of a metal, an alloy, a conductive ceramic, and a conductive polymer material is provided outside the sintered layer.

As the flexible planar ceramic body in the present invention, a woven or nonwoven fabric made of ceramic fibers, or a ceramic sheet or film is suitable. As the ceramic fiber forming the former woven or nonwoven fabric, a silicon carbide (SiC) fiber or an oxide fiber can be used. These ceramic fibers are continuous filaments and the average diameter is, for example, 10
It has an extremely small size of about 13 μmφ, high heat resistance (1000 ° C. or higher) and high tensile strength (200 kg / mm ² ). For example, Tyranno fiber: SiC fiber (Si-T manufactured by Ube Industries, Ltd.)
i-CO type) Product name Nicalon: Product name of SiC fiber manufactured by Nippon Carbon Co., Ltd. Saphir: Imperial Chemical Industries PLC-IC, UK
Other SiO ₂ fibers are known, such as I ₂ Al ₃ fiber brands. On the other hand, the latter ceramic sheet or ceramic film can be obtained by molding the woven or nonwoven fabric.

The volume resistivity of the above ceramic sheet is 10 ⁵ Ωcm
It is desirable that: The reason for this is to reduce the occurrence of loss when the temperature of the superconducting material rises above the critical temperature and to prevent breakdown.

As a sintered layer formed on the outside of the ceramic planar body, YBa ₂ Cu ₃ Ox (x <14; perovskite) may be mentioned as a typical example, but it is needless to say that the present invention is not limited to this. And other ceramic superconducting materials can also be used. This sintered layer is formed by applying a superconducting substance or a solution in which this fine powder is dispersed on a ceramic surface, and then sintering or
Alternatively, it is formed by depositing a constituent material that generates a superconducting material by heat treatment in an oxidizing atmosphere on a ceramic planar body, and then sintering it. The main ones of these adherends are a Y-Ba-Cu alloy solution, a mixed solution of oxides and carbonates of Y, Ba and Cu, a gas phase or ion Y by plasma discharge, vapor deposition, thermal spraying, sputtering, or the like. Ba, fatty acids each containing Cu, metal salts other than alkali salts such as naphthenic acid, i.e. metallic soaps Y, Ba, solvent nitrate Cu, the fine powder of the mixed solution YBa ₂ Cu ₃ Ox of the oxalate was dispersed in a solvent There is a mixed solution dispersed inside.

In this case, it is desirable to mix the respective constituent materials at a predetermined atomic number ratio except when the superconducting material itself is applied.

The sintering of the adherend is performed at 700 to 1000 ° C. or higher. In this case, it is preferable to heat in an oxygen stream or under oxygen pressure.

The superconducting stabilization layer formed outside the sintered layer is, for example,
Cu, Al, Ag, or an alloy thereof is used, and this layer is formed by plating, vapor deposition, or the like. This superconducting stabilization layer acts as a thermal stabilizer (that is, acts as a bypass for the current when the superconducting material locally generates heat, preventing the transition to normal conduction due to the heat from being cascaded and destroying superconductivity). Is provided for the purpose of improving chemical stability and facilitating mechanical protection and terminal attachment.

In this case, when Ag, Au, Pt or an alloy thereof that does not generate an oxide at a high temperature is used as a stabilizing material, a heat treatment for generating a ceramic superconducting material can be performed after coating the stabilizing material. These stabilizers do not react with the ceramic inside during heat treatment, moderately restrict the supply of oxygen from the outside, prevent powdering and burning due to rapid solidification, and produce dense crystals over a long period of time can do.

Further, a conductive ceramic or a conductive polymer material is used as a stabilizer. The former conductive ceramics include carbides such as TiC, NbC, WC, TaC, ZrB, BN, and ZrN,
There are borides and nitrides, while the latter conductive polymer materials include polyacetylene and polypyrrole. These stabilizers have a volume resistivity of 10 ⁵
It is preferably Ωcm or less. The reason is the same as in the case of the ceramic planar body, but particularly when conductive ceramics are used, the difference in thermal expansion of the constituent members of the wire can be reduced, which is extremely advantageous for thermal effects.

The coating of these stabilizing materials can be applied in a molten, gaseous or ionic state, similar to the superconducting material deposition.
An insulating coating is usually applied outside the superconducting stabilization layer. As this insulating coating, an organic insulating material such as a UV-curable urethane resin or PVF enamel resin, or an inorganic insulating material such as alumina or polyborosiloxane resin can be used.

(Function) In the present invention, a sintered layer made of a ceramic superconducting material, a metal or an alloy, or a conductive ceramic or a conductive polymer material is formed on one or both sides of a flexible ceramic planar body. Since a superconducting stabilization layer is provided in order, a lightweight and flexible magnetic shield material can be obtained, and this shield material is also effective against a static magnetic field and a strong magnetic field.

Further, since the planar body is made of ceramics, the difference in thermal expansion with the superconducting material is small and the adhesion is excellent.

(Example) As shown in FIG. 1, a woven fabric (1) made of Tyranno fiber (trade name of Si-Ti-CO ceramic fiber manufactured by Ube Industries, Ltd.) was formed on both surfaces by a solid phase reaction method. YBa ₂
Fine powder (2) of Cu ₃ Ox is 5 to 6 μm by plasma spraying
To the thickness of. Next, the woven fabric was heated at 950 ° C. for 18 hours and then oxidized and sintered at 1000 ° C. for 1 hour. FIG. 2 shows the superconducting characteristics (critical temperature; Tc) of the shield material (4) in which silver (3) was deposited to a thickness of 1 μm on both outer sides of the sintered layer.
As is clear from this figure, Tc is about 85K, and the liquid nitrogen temperature (77K) has a sufficient magnetic shielding effect.

[Effects of the Invention] As described above, the superconducting material for a magnetic shield of the present invention is lightweight, has excellent flexibility, and is effective for a static magnetic field, a slowly changing magnetic field or a strong magnetic field.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing one embodiment of a magnetic shield material according to the method of the present invention, and FIG. 2 is a graph showing its superconducting characteristics. 1 Woven cloth 2 YBa ₂ Cu ₃ Ox coating layer 3 Silver stabilization layer 4 Magnetic shielding material

Continuation of the front page (72) Inventor Toshio Kasahara 2-1-1 Oda Sakae, Kawasaki-ku, Kawasaki City, Kanagawa Prefecture Inside Showa Electric Wire & Cable Co., Ltd. (72) Inventor Masatada Fukushima 2-1-1 Oda Ei, Kawasaki-ku, Kawasaki City, Kanagawa Prefecture No. 1 Inside Showa Electric Wire & Cable Co., Ltd. (56) References JP-A-64-82697 (JP, A)

Claims (5)

(57) [Claims] A sintering layer made of a ceramic superconducting material is provided on one or both sides of a flexible planar ceramic body, and a metal or alloy, a conductive ceramic or a conductive polymer is provided outside the sintering layer. A superconducting material for a magnetic shield, comprising a superconducting stabilizing layer made of any one of materials. 2. The superconducting material for a magnetic shield according to claim 1, wherein the ceramic planar body is a woven or non-woven fabric made of ceramic fibers. 3. A superconducting material for a magnetic shield according to claim 1, wherein the ceramic planar body is a ceramic sheet or a ceramic film. 4. The superconducting material for a magnetic shield according to claim 1, wherein the ceramic planar body is made of a silicon carbide or oxide ceramic. 5. The superconducting material for a magnetic shield according to claim 1, wherein the superconducting material is a Y—Ba—Cu—O-based ceramic.