JPH0269997A - Ceramic superconductive magnetic shield and manufacture of the same - Google Patents

Abstract

PURPOSE:To make it possible to manufacture a magnetic shield which shows magnetic shield effect at liquid nitrogen temperature and has a larger, complex shape by forming a ceramic superconductive layer on the surface of a board. CONSTITUTION:An organic binder and solvent are mixed to powders of a ceramic superconductive material and a ceramic superconductive paste is obtained. This ceramic superconductive paste is applied on the inner surface of a zirconia-ceramic-made pipe 1 and burned in oxygen to form a superconductive layer 2. This makes it possible to manufacture a magnetic shield which shows magnetic shield effect at liquid nitrogen temperature and has a larger, complex shape. The superconductive layer 2 should preferably contain a metal or its oxide of 0.1 to 50 weight parts with respect to a ceramic superconductive material 100.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic shield using a ceramic superconductor and a method for manufacturing the same.

〔overview〕

The present invention provides a ceramic superconducting magnetic shield in which more than one ceramic superconductor layer is laminated, which exhibits a magnetic shielding effect at liquid nitrogen temperature by forming the ceramic superconductor layer on the surface of the base material, and is large in size. Another object of the present invention is to provide a magnetic shielding body that can be manufactured even if it has a complicated shape, and a method for manufacturing the magnetic shielding body.

[Conventional technology]

In recent years, various magnetic generation devices, particularly medical devices using superconducting magnets, have been widely used.

Such devices require magnetic shielding to protect the human body. Furthermore, magnetic shielding is also required to prevent digital electronic equipment from generating unnecessary electromagnetic waves and from malfunctioning of the equipment due to these electromagnetic waves.

As magnetic shielding materials, metal magnetic materials such as high magnetic permeability ipermalloy and silicon steel plates have been used.

However, since these magnetic materials have finite magnetic permeability, superconducting quantum interference devices (SQUIDs) are used in the field of biomagnetic measurement, which measures weak magnetic fields in living organisms such as those generated by the brain and heart. It was insufficient for magnetic shielding.

Therefore, magnetic shielding materials for 5QUID using metallic superconducting materials have been put into practical use. Complete magnetic shielding is theoretically possible by utilizing the Meissner effect of superconducting materials.

[Problem that the invention seeks to solve]

However, metallic superconducting materials require liquid helium for cooling, making it impossible to magnetically shield a 5QUID that operates at liquid nitrogen temperatures. Therefore, magnetic shielding materials using ceramic superconducting materials are being considered.

The magnetic shield body for 5QUID basically has a pipe shape to shield magnetic fields from the surroundings.

To manufacture a magnetic shield with ceramic superconductor,
One possibility is to sinter superconductor powder into a pipe shape.

However, this method has the disadvantage that a liquid phase tends to be partially formed during sintering, resulting in deformation. In addition, it has the drawback of poor processability and the inability to manufacture large-sized products. Furthermore, while a multilayer structure has a better magnetic shielding effect than a thick single layer structure, it is difficult to create this structure using bulk materials. Although it is possible to use a superconducting thin film, the disadvantage is that it is difficult to manufacture large thin films or those with complicated shapes.

An object of the present invention is to solve the above problems and provide a superconducting magnetic shield using a ceramic superconductor and a method for manufacturing the same.

[Means for Solving the Problems] The ceramic superconducting magnetic shield of the present invention is characterized in that a layer of ceramic superconductor is formed on the surface of a supporting base material.

Ceramic superconductor materials constituting the superconductor layer include: - one or both of alkaline earth elements, yttrium and ranknid elements, and oxides containing copper, and - one or both of bismuth and button. , strontium, calcium and copper as constituents; ■ oxides as constituents of potassium, barium, calcium and copper; ■ oxides as constituents of barium, potassium and/or lead, and bismuth. objects etc. can be used.

The superconductor layer preferably contains 0.1 to 50 parts by weight of a metal or its oxide based on 100 parts by weight of the ceramic superconductor material. As a result, a superconductor layer that is dense, has a high adhesive density with the supporting substrate, and has a high critical temperature and critical current density can be obtained. As a result, the magnetic shielding effect is significantly improved compared to the case where the metal or its oxide is not included.

Further, it is desirable to provide a protective film on the surface of the superconductor layer to prevent reaction with moisture and carbonated water. Ceramic superconductors, especially oxygen-deficient perovskite type 3a2
When the YCu307-y superconductor (y is the amount of oxygen vacancies) adsorbs moisture or carbonated water, it decomposes and its superconducting properties deteriorate significantly. In particular, in the case of thick films formed by coating or screen printing, it is difficult to densify them compared to bulk films.
Significant deterioration occurs due to adsorption of moisture and carbonated water. However, by providing a film on its surface, a ceramic superconducting magnetic shield whose characteristics do not change even after repeated use can be obtained.

As a protective film, glass materials such as borosilicate glass and crystallized glass, metals and alloys such as gold, silver, platinum, and palladium, wax, fest, polyester resin,
Materials such as organic materials such as phenolic resins, epoxy resins, polyimide resins, and fluoroplastics that have a low reaction with superconducting substances, are airtight, and do not crack due to temperature changes between liquid nitrogen temperature and room temperature. Are suitable. As a method for forming the film, the material may be coated, printed, or impregnated, or physical vapor deposition such as vapor deposition, sputter linking, or plating method may be used. Further, when glass is used as a film, heat treatment may be performed. The suitable thickness of the film is about 1 to 100 μ0, but it may be thicker if no cracks occur.

It is desirable to provide a magnetic layer on the surface of the superconductor layer, or in the case where a protective film is provided, between the superconductor layer and the protective film or on the surface of the protective film. This magnetic layer is a magnetic material that exhibits a magnetic shielding effect at a temperature at which the ceramic superconductor contained in the superconductor layer exhibits superconducting properties, that is, a magnetic material that has high magnetic permeability and high saturation magnetic flux density. desirable. Furthermore, it is desirable that the material be a magnetic material that exhibits a magnetic shielding effect even above the critical temperature of the superconductor layer. Such materials include Fe containing permalloy composition.
-Ni alloy, silicon steel plate and other metal materials, or ferrite materials are used. To form a film of these materials on the surface of the superconductor layer, vapor deposition, sputtering, other physical film formation, or plating method is used.

The supporting base material for the superconductor layer is preferably one that has low reactivity to the ceramic superconductor contained in the superconductor layer, and is preferably one containing zirconium oxide, magnesium i12ide, strontium titanate, or at least one of these as a main component. Ceramic materials are suitable. Furthermore, a film formed of these ceramic materials on the surface of an alumina or other ceramic substrate can also be used.

Further, it is also possible to use a substrate made of alumina or other ceramics on which a metal film such as silver, gold, platinum, palladium or the like is formed.

Further, it is desirable that the supporting base material includes a magnetic layer. This magnetic layer is preferably made of a magnetic material that exhibits a high magnetic rate at a temperature at which the ceramic superconductor contained in the superconductor layer exhibits superconducting properties. Between the magnetic material layer and the superconductor layer, it is necessary to provide a film of the above-mentioned ceramic material or a metal film in order to prevent a reaction between the magnetic material and the ceramic superconductor.

To manufacture such a ceramic superconducting magnetic shield, a ceramic superconductor paste, which is a mixture of powdered ceramic superconductor material, an organic binder, and a solvent, is coated or printed on a supporting substrate, and the ceramic superconductor paste is coated or printed on a supporting substrate. Burn the body paste. Alternatively, the superconductor powder may be thermally sprayed onto the surface of the support base material and heat treated, for example, in an oxidizing atmosphere.

It is desirable to mix powder of a metal or its oxide with the powder of the ceramic superconductor material.

This powder may be a metal, an alloy, a mixture containing these, or an oxide thereof that melts at the firing temperature of the ceramic superconductor material in an oxygen-containing atmosphere, or a metal oxide or a mixture thereof that desorbs oxygen. good. As such metals and metal oxides, gold, silver, platinum, palladium or mercury, alloys and mixtures containing these, oxides of these, mixtures of oxides, mixtures of metals and oxides, etc. can be used. can. The mixing ratio of the metal or metal oxide is 0.00 to 100 parts of the ceramic superconductor material.
A range of 1 to 50 parts by weight is desirable. If this range is
A superconductor layer that has excellent adhesion to the substrate, is sufficiently dense, and has a high critical temperature and critical current density can be obtained.

Examples of organic binders include ethyl cellulose, nitrocellulose, and other cellulose resins, polymethyl methacrylate and other acrylic resins, alkyd phenol resins, vinyl resins, epoxy resins, and other materials that undergo thermal decomposition easily in the firing atmosphere. Any material may be used as long as it is suitable.

As the solvent used for pasting, carpitol acetate, terpineol, toluene, xylene and other aromatic solvents, ethyl acetate and other ester solvents, methyl ethyl ketone and other ketone solvents, or mixed solvents thereof can be arbitrarily used.

[For production]

By forming the ceramic superconductor on the surface of the support base material, a magnetic shield body can be manufactured in the shape of the support base material.

Therefore, not only can large-sized magnetic shielding bodies be easily manufactured, but also those having complicated shapes can be manufactured easily. Moreover, a magnetic shielding body having a multilayer structure can be easily manufactured.

〔Example〕

(Example 1) Barium carbonate BaC0+, diytrium trioxide Y20°, and cupric oxide CuO were used as starting materials, and these were mixed and subjected to the usual ceramic manufacturing procedures, that is, calcination, pulverization, granulation/molding, and Firing was performed to obtain a ceramic superconductor. Calcination and firing are performed in the atmosphere, and
After heating at 25°C for 20 hours, it was cooled at a rate of 50°C/hour.

Regarding the ceramic superconductor obtained in this way,
Using zirconia balls, the material was time-pulverized in ethanol under a cloud of dry nitrogen gas for 10 hours.

As a result, a ceramic superconductor material powder having an average particle size of 1 μm was obtained. This powder was divided into two parts, and 30 parts by weight of silver oxide powder (particle size: 0.5 μm) was mixed into one part.

Next, ethyl cellulose, butylbenzyl fucrate, and terpineol were mixed with the obtained powder, and the mixture was stirred and mixed in a dry nitrogen atmosphere using a crusher, taking care not to dry it, and the paste was formed into a ceramic superconductor paste. I got it.

An example of a ceramic superconducting magnetic shield using this ceramic superconductor paste is shown in the figure.

In this example, we used a ceramic superconductor paste with an inner diameter of 20 m.
The mixture was coated on the inner surface of a zirconia ceramic pipe 1 having an outer diameter of 25 mm and a length of 100 mm, and was fired at 985° C. for 3 minutes in oxygen to form a superconductor layer 2 with a thickness of 100 μm.

This ceramic superconducting magnetic shield was immersed in liquid nitrogen, a Hall element for cryogenic temperatures was placed inside the pipe, and a magnetic field was applied perpendicular to the pipe from the outside to measure the magnitude of the internal magnetic field. The results are shown in Table 1.

(Hereinafter, this page margin) As shown in Table 1, a magnetic shielding effect can be obtained by the superconductor layer. At this time, adding silver oxide to the superconductor layer further improves the magnetic shielding effect.

(Example 2) Zirconia alkoxide 2r, which is a group 1 alkoxide, was placed on the inner surface of a Ni-Zn ferrite magnetic material processed into a pipe shape with an inner diameter of 20 mm, an outer diameter of 25 mm, and a length of 100 mm.
(DC2H5) 4 liquid was applied and dried with hot air for 5 minutes in the atmosphere at a temperature of 50°C. Next, set this to 1200
C. for 1 hour to obtain a pipe with a zirconia oxide film formed on the inner surface.

This pipe was used as a support base, and the ceramic superconductor paste mixed with silver oxide obtained in Example 1 was applied to the inner surface of this support base. Furthermore, this was fired in oxygen at 985° C. for 3 minutes to form a superconductor layer with a thickness of 100 μm. Furthermore, a protective film was formed on the surface of the superconductor layer using fluorocarbon resin.

This ceramic superconducting magnetic shield was immersed in liquid nitrogen, a Hall element for cryogenic temperatures was placed inside the pipe, and a magnetic field was applied perpendicular to the pipe from the outside to measure the magnitude of the internal magnetic field. The results are shown in Table 2. This table shows measured values when no superconductor layer is provided as a comparative example.

(Hereinafter, unfaithful margin) Table 2 Comparing the measured values shown in Table 2 with the measured values shown in Table 1, it can be seen that Example 2 shows a greater magnetic shielding effect up to a higher magnetic field.

For each example, repeated measurements were performed using liquid nitrogen and room temperature, and the coating condition of the superconductor layer surface, cracks,
No cracks or other changes were visually observed.

〔Effect of the invention〕

As explained above, the ceramic superconducting magnetic shield of the present invention exhibits a magnetic shielding effect not only against a weak magnetic field but also against a relatively large magnetic field.

According to the present invention, it is possible to easily manufacture large magnetic shielding bodies, and also to manufacture magnetic shielding bodies having complicated shapes. Further, a multilayered magnetic shielding body can be easily manufactured. Therefore, the present invention is highly effective as a magnetic shield for equipment used at liquid nitrogen temperatures.

[Brief explanation of the drawing]

The figure is a perspective view of a ceramic superconducting magnetic shielding body according to an embodiment of the present invention. ■... Zirconia ceramic pipe, 2... Superconductor layer. Patent applicant Mitsubishi Mining Cement Co., Ltd. Representative Patent attorney Naotaka Ide

Claims (13)

[Claims] 1. 1. A ceramic superconducting magnetic shield comprising at least one laminated ceramic superconductor layer, characterized in that the superconductor layer is formed on the surface of a support base material. 2. 2. The ceramic superconducting magnetic shield according to claim 1, wherein the superconductor layer contains 0.1 to 50 parts by weight of a metal or an oxide thereof based on 100 parts by weight of the ceramic superconductor material. 3. 2. The ceramic superconducting magnetic shield according to claim 1, wherein a protective film is provided on the surface of the superconductor layer to prevent reaction with moisture and carbonated water. 4. Claim 1, wherein a magnetic layer is provided on the surface of the superconductor layer.
The described ceramic superconducting magnetic shield body. 5. 5. The ceramic superconducting magnetic shield according to claim 4, wherein the magnetic layer is a magnetic material that exhibits a magnetic shielding effect at a temperature at which the ceramic superconductor contained in the superconductor layer exhibits superconducting properties. 6. The ceramic superconducting magnetic shield according to claim 1, wherein the supporting base material includes a magnetic layer. 7. 7. The ceramic superconducting magnetic shield according to claim 6, wherein the magnetic layer contains a magnetic material that exhibits a magnetic shielding effect at a temperature at which the ceramic superconductor contained in the superconductor layer exhibits superconducting properties. 8. 2. The ceramic superconducting magnetic shield according to claim 1, wherein the supporting base material is provided with a film having low reactivity to the ceramic superconductor contained in the superconductor layer at an interface in contact with the superconductor layer. 9. 9. The ceramic superconducting magnetic shield according to claim 8, wherein the less reactive film contains any one of zirconium oxide, magnesium oxide, strontium titanate, silver, palladium, or platinum. 10. A method for manufacturing a ceramic superconducting magnetic shield, in which a ceramic superconductor paste, which is a mixture of ceramic superconductor powder, an organic binder, and a solvent, is applied to a supporting base material, and the ceramic superconductor paste is fired. 11. 11. The method for manufacturing a ceramic superconducting magnetic shield according to claim 10, wherein the ceramic superconductor material powder contains 0.1 to 50 parts by weight of metal or oxide powder based on 100 parts by weight of the ceramic superconductor material. 12. 11. A film having low reactivity with the ceramic superconductor substance contained in the ceramic superconductor paste is formed on the surface of the support base before the ceramic superconductor paste is applied to the support base. A method for manufacturing a ceramic superconducting magnetic shield. 13. 11. The method for manufacturing a ceramic superconducting magnetic shield according to claim 10, wherein a magnetic layer is formed on the surface of the ceramic superconducting paste after firing the ceramic superconducting paste.