JPH01151299A - Preparation of plate shield material - Google Patents

Abstract

PURPOSE:To make it possible to easily manufacture a compact and light plate shield material having a high shield efficiency, by combining an oxide superconductor or its precursor in a predetermined quantity and dissolving it in an atmosphere containing oxygen and then specifying the condition of fabrication and heating treatment. CONSTITUTION:An oxide superconductor or its precursor is combined by a predetermined quantity and dissolved in an atmosphere containing oxygen. This dissolved substance is fabricated into a desired configuration while cooled to at least 950 deg.C at a speed of 10 deg.C/sec or more and then subjected heating treatment in the oxygen containing atmosphere at a temperature of 500 deg.C or higher for 10 minutes or more. As a raw material to be dissolved, an oxide superconductor or its precursor such as YBa2Cu3O7 is used, and as the precursor substance, an inorganic compound such as an oxide of an element constituting a superconductor, carbonate or nitrite, an organic compound such as alkoxide or complex salt, metal of a construction element or its alloy is used. As a result, it is possible to manufacture a compact, light and inexpensive plate shield material using the Meissner effect in the oxide superconductor.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for manufacturing a plate-shaped shield material.

[Conventional technology and its problems]

In equipment that uses strong electromagnetism, such as motors, transformers, magnetic levitation trains, MRr-CT packing equipment (nuclear magnetic medical diagnostic equipment), and magnetic separators, magnetic flux may leak to the outside and cause malfunctions of other electrical and electronic equipment. There are also concerns that it may have harmful effects on the human body.

For this reason, in the above-mentioned devices, measures are taken to cover the device with a magnetic material such as an iron plate in order to prevent magnetic flux from being emitted to the outside, and in order to shield magnetic flux from the outside in the case of precision magnetic measurement devices. It is being However, this increases the size and weight of the entire device, which poses a practical problem.

To solve this problem, shielding technology that utilizes the Meissner effect of superconductors has been put into practical use in some superconducting equipment, but since metal superconductors are used as the shielding material, liquid He is required as a coolant, making it economical. The disadvantage is that the scope of use is limited.

By the way, in recent years, (Ln+-xs rx) Cuba, (Ln,-, BaX) which becomes superconducting at liquid nitrogen temperature (77K)
), Cub, LnBa, Cu5Oy, LnBa
Oxide superconductors with a layered perovskite structure, such as z-xsr and cusOt (where Ln is Y, Sc, or a rare earth element), have been found, but these oxide superconductors are brittle and cannot be used as metal materials. It was difficult to industrially produce an effective shielding material because plastic working could not be performed on the material. Therefore, this oxide superconductor is processed by PV process such as sputtering method.
Attempts have been made to process the material using a method, but this method involves scattering the component elements in a vacuum and precipitating them in the form of a film on a support material over a long period of time, resulting in poor productivity.
Attempts have also been made to mold the powder or make it into a paste, print a thick film on a support material, and sinter it.
Not only is the process not necessarily simple, but it also has the disadvantage that a sufficient shielding effect cannot be obtained. The cause of this is
This is thought to be due to the fact that individual particles have different superconductivity, some of them are non-superconducting, and that there are large amounts of non-superconducting parts such as crystal grain boundaries and vacancies.

[Means and effects for solving the problems] The present invention was made in view of the above situation, and its purpose is to provide a small, lightweight, and inexpensive plate-shaped shield that utilizes the Meissner effect in oxide superconductors. The object of the present invention is to provide a method for manufacturing materials.

That is, in the present invention, the oxide superconductor is prepared by blending a predetermined amount of its precursor, melting it in an oxygen-containing atmosphere, and then cooling the melt to at least 950°C at a rate of 10° (:/sec or more). The molded product is then molded into a desired shape, and then heat-treated in an oxygen-containing atmosphere at 500° C. or higher for 10 minutes or more.

In the present invention, an oxide superconductor such as YBa, Cu, O, or a precursor thereof is used as a raw material for melting.
As the latter precursor, inorganic compounds such as oxides, carbonates, and nitrates of the elements constituting the superconductor, organic compounds such as alkoxides and complex salts, metals of the constitutive elements, alloys thereof, and the like are used.

The above precursor is converted into YB az Cu x O? To give a concrete explanation using the superconductor as an example, Y is Y2O
3, Y(NOs)s, Y (CHs COO)s, Y alone, Ba is Ba(OH)x, Ba (No,), Ba
C0,,83 soap, Cu is CuzO, CuO1Cu
(OHh, CuSOa, Cu(Now)t, acetylacetate, Cu powder, Cu-Ba, etc.

It is also possible to mix a predetermined amount of the above-mentioned raw materials, pre-sinter this mixture to form an oxide mixture or superconductor oxide, and process this into powder, rod-shaped bodies, blocks, etc. for use.

In the present invention, the above raw materials are heated to 1200°C in a crucible etc.
The material is heated and melted as described above, and the heat source used at this time may be electricity, infrared rays, electron beams, laser light, or the like.

The above-mentioned rod-shaped bodies can also be melted by directly exposing them to a beam such as infrared rays.

The reason why raw materials are melted and formed into a plate shape in the present invention is as follows.
This is because the blended components become uniform in a short time, and a homogeneous dense body close to the theoretical density can be obtained. Zero melting! When carried out in a containing atmosphere, O2 defects in the superconductor are prevented, and the post-process heat treatment conditions can be carried out at a low temperature and in a short time. 00 in the atmosphere
When the partial pressure is 5 atm or more, especially 15 to 200 atm, 0
．． is sufficiently supplied, and characteristics such as Jc are further improved.

In the present invention, the melt is heated to 10' (:
The reason for cooling to at least 950'C at a cooling rate of /sec or more is to make the crystal &1Ila of the obtained molded body dense, and to take the example of YBazCu, O, superconductors, the above superconductors are Y2O1, CugO1BaCuO□, etc. This is because it suppresses phase separation, and even if phase separation occurs, each phase is finely dispersed, so it can be easily homogenized in the heat treatment in the subsequent step. The molten material is cooled by injecting or contacting the molten material into a mold or a cooling body, and the cooling rate is particularly preferably 50'C/see or higher.

In the present invention, the molded body obtained by cooling the melt is
The reason for performing the heat treatment in an Ox-containing atmosphere at a temperature of .degree. C. or higher is to maximize the formation of a superconductor phase in the compact and to eliminate harmful thermal strain during cooling molding.

In the above, the heat treatment may be carried out by directly holding the melt at a predetermined heat treatment temperature from the temperature at which it was cooled at a predetermined rate, or by -
It may be reheated after cooling to room temperature.

When the molded body is finished to desired dimensions and then subjected to heat treatment, additional effects such as removal of processing strain can be obtained.

In the present invention, the above-mentioned heat treatment is carried out at a temperature range of 500°C or more, preferably 500 to 950°C, for 10 minutes or more, preferably for 1 to 24 hours, at a partial pressure of 0.2 atm or more, particularly preferably 1 It is practical to perform the treatment in an atmosphere of ~5 atmospheres. In the above, the 08 partial pressure in the atmosphere is 0.2
If the pressure is less than atmospheric pressure, it will not be possible to obtain a material that exhibits a sufficient shielding effect.

The shielding material of the present invention can be molded all at once using a mold of a predetermined shape, but it may also be cut into a desired shape from a large molded body, or the superconductor can be formed into a tile-shaped molded body.
This can be used by bonding to a metal plate, ceramic plate, plastic plate, etc. A other than Fe as a metal plate
By using L, Cu, Ni, or an alloy thereof, an electromagnetic shielding effect can be provided at the same time. For bonding to the metal plate, it is desirable to use a metal brazing material such as solder to provide electrical and thermal continuity.

The shielding material of the present invention is made into a molded body as described above and used to surround magnets and electrical and electronic equipment.In order to provide this with a shielding effect, the molded body must be heated to below its own critical temperature (T). If cooling is required and therefore T is below room temperature, the molded body is used by being disposed within the cooling medium flow path or on the inner and outer surfaces of the cooling tube body.

〔Example〕

Next, the present invention will be explained in detail with reference to examples.

Example 1 Erg's, Y2O2, BaC0, CuO
:Ba:Cu in atomic ratio 1:2:3 (however, Er:Y-1
:4), put it in a platinum crucible, heated and melted it in the atmosphere at 1.360°C, and then melted it at 10.
The mixture was poured into a 3 m x 3 m iron mold and formed into a tile shape, which was then subjected to heat treatment under various conditions. The cooling rate during melt cooling was adjusted to various rates by using a cooling medium in the mold.

Conventional Example 1 The same raw material used in Example 1 was heated to 900"C6 in the air.
The powder obtained by pulverizing the calcined product is press-molded, and this molded body is made into a 0. 950'C2H and 7 in air flow
It was heated and sintered at 00°C for 24 hours.

For each sample thus obtained, the relative density and magnetic flux density in liquid nitrogen were measured, and the shielding efficiency was calculated using the following formula.

sX: Magnetic flux density when a sample is sandwiched between an electromagnet and a glass meter.

Xo: Magnetic flux density (750 Gauss) when no sample is sandwiched.

The results obtained are shown in Table 1 along with the manufacturing conditions.

As is clear from Table 1, the products manufactured by the present invention (1 to 4) exhibit higher values in both relative density and shielding efficiency than product 8 produced by the conventional method.

Among the comparison method products, the one with a slow melting and cooling rate (5), the one with a short heat treatment time (6), and the one with a low heat treatment temperature (7) all have low shielding efficiency values.

Example 2 Y2O2, B a CO2, S r COz, CuO Y: (Ba + Sr): Cu (However, Ba: 5r = 4
: l) are blended in an atomic ratio of 1:2:3,
Next, this was calcined for 6 hours at 920°C in the atmosphere, crushed and formed into a rod shape, and then heated and sintered at 800°C for 6 hours. Apply infrared rays to the lower end of the solid to gradually melt it from the lower end.
This melt was heated to 900°C to create a 100mm x 3m
It was dropped into an iron mold with a diameter of 1.2 m. After the dropping was completed, the mold was cooled and the resulting molded body was cooled to 500°C, and then this solidified body was heat-treated at 800°C for 5 hours in an Ot atmosphere at 2 atm. The atmosphere in the pressurized container and the cooling rate of the molded body were varied variously.

The results are shown in Table 2 together with the manufacturing conditions.

As is clear from Table 2, the products manufactured by the present invention (9 to 12) exhibit higher values in both relative density and shielding efficiency than the products produced by the conventional method (8 in Table 1).

Among the comparison method products, the shielding efficiency of both Oa, which omitted the heat treatment, and Oa, which did not include O2 gas in the atmosphere of the heat treatment, was significantly reduced.

〔effect〕

As described above, according to the present invention, it is possible to easily produce a plate-shaped shielding material that is small, lightweight, and has high shielding efficiency that operates effectively at liquid nitrogen temperature, and therefore has a significant industrial effect.

Claims (2)

[Claims] (1) After blending a predetermined amount of an oxide superconductor or its precursor and melting it in an oxygen-containing atmosphere, the melt is cooled to at least 950°C at a rate of 10°C/sec or more and shaped into a desired shape. 1. A method for manufacturing a plate-shaped shield material, which comprises molding the molded product into a material, and then heat-treating the molded product in an oxygen-containing atmosphere at 500° C. or higher for 10 minutes or more. (2) Production of a plate-shaped shield material according to claim 1, wherein the oxygen partial pressure in the oxygen-containing atmosphere is 5 atm or more during melting and cooling, and 0.2 atm or more during heat treatment. Method.