JPH04302499A - Manufacture of magnetic shield body - Google Patents

Abstract

PURPOSE:To manufacture a magnetic shield body wherein an oxide high- temperature superconductor is used and which is high in shield property. CONSTITUTION:The sintered body of an oxide high-temperature superconductor such as Bi and Ti is baked again after hydrostatic pressurization treatment. The obtained magnetic shield body is high in density, and can shield a high 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 of manufacturing a magnetic shield, and more particularly to a method of manufacturing a magnetic shield using an oxide-based high-temperature superconductor.

[0002] A magnetic shield using a superconductor shields the internal space of the magnetic shield placed in a magnetic field from an external magnetic field, or shields a magnetic field generating source placed inside the magnetic shield from an external magnetic field. used to prevent magnetic leakage.

[0003] In recent years, intensive research has been conducted on magnetic shielding materials that utilize oxide-based high-temperature superconductors that exhibit superconductivity above the liquid nitrogen temperature. After filling a mold with powder that would become a superconductor, it was press-molded and fired.

0004

[Problems to be Solved by the Invention] However, in the above-mentioned method using press forming, a superconducting phase is generated during firing of the compact and superconductor particles grow, resulting in a decrease in the density of the sintered compact. , the magnetic shielding properties deteriorated, and it was difficult for the obtained magnetic shielding body to shield high magnetic fields.

[0005]

[Means for Solving the Problems] As a result of repeated research in order to solve the above problems, the present inventors have improved the magnetic shielding properties by repressurizing a molded body of an oxide-based high temperature superconductor. I was able to force it.

That is, the present invention is a method for manufacturing a magnetic shielding body, which is characterized in that a sintered body of an oxide-based high-temperature superconducting material is hydrostatically pressed and then fired again.

(Oxide-based high-temperature superconducting material) The oxide-based high-temperature superconducting material used in the present invention is a material that becomes an oxide-based high-temperature superconductor that exhibits superconducting properties at temperatures above the liquid nitrogen temperature when fired. So, as such a high-temperature superconductor,

[0009] Ba2YCu3Oy (firing temperature 900-950°C) Bi2Sr2Ca2Cu3Oy
(Firing temperature 800-900°C) Bi2
Sr2Ca1Cu2Oy (firing temperature 80
0~900℃) Tl2Ba2Ca2Cu3Oy
(Calcination temperature 900-1000℃) Bi2-xPb
xSr2Ca2Cu3Oy (calcination temperature 800-90
0℃) Bi2-xPbxSr2Ca1Cu2Oy (
Firing temperature: 800 to 900°C), etc.

(Sintered body) Conventional methods can be used to produce the molded body of the present invention, and the method is not particularly limited, but for example, press molding, doctor blade molding, extrusion molding, etc. Process it into the final shape you need.

The processed molded body is fired into a sintered body by a conventional method for ceramics. That is, the desired sintered body can be obtained by firing the obtained molded body at a temperature suitable for each high-temperature superconductor composition.

(Isostatic pressure treatment) In the method of the present invention, the sintered body obtained above is subjected to a hydrostatic pressure treatment. That is, the sintered body is sealed in a plastic container made of rubber or the like, and a uniform pressure is applied to the container through the liquid. This improves the density of the sintered body. The pressure applied in hydrostatic pressure treatment is
300 kg/cm2 or more is preferable. pressure is 300k
If it is less than g/cm2, the effect of improving the density cannot be expected much.

(Re-firing) The sintered body subjected to the hydrostatic pressure treatment is re-fired to form a magnetic shield body. That is, the sintered body subjected to the hydrostatic pressure treatment is re-sintered at a temperature suitable for each high-temperature superconductor composition.

[0014] By repeating the hydrostatic pressure treatment and re-firing, a magnetic shielding body with even higher density can be obtained. There is no particular limit to the number of repetitions, but
Preferably 1 to 3 times.

The obtained sintered body may be machined into a predetermined shape if necessary when used as a magnetic shielding body.

[0016]

EXAMPLES The present invention will be explained in detail below using examples.

Example 1 As raw material powder, the molar ratio is Bi:Pb:Sr:Ca:C
Bi2O3, PbO, SrCO3, C so that u=1.92:0.48:2.0:2.0:3.2
After blending aCO3 and CuO, adding ethanol and mixing with a resin mill and resin ball, drying, and calcining the obtained powder at 850°C for 50 hours to obtain Bi1.8P.
b0.2Sr2Ca2Cu3Oy oxide-based high temperature superconducting powder was produced.

[0018] This powder was press-molded at a molding pressure of 350 kg/cm2, and subjected to isostatic pressure treatment at a pressure of 1500 kg/cm2, resulting in an outer diameter of 45 mm, an inner diameter of 8 mm, and a length of 60 m.
A tubular molded body of m was obtained.

[0019] This molded body was fired at 850°C for 100 hours in an air atmosphere, allowed to cool in a firing furnace, and had a density of 4.5.
A tubular sintered body of g/cm3 was obtained.

Next, the tubular sintered body obtained above was subjected to isostatic pressure treatment at a pressure of 1500 kg/cm2, and fired again at 850° C. for 50 hours in an air atmosphere to reduce the outer diameter to 40.
mm, inner diameter 10mm, length 50mm, density 5.2g/c
A tubular magnetic shield body of m3 was obtained.

[0021] While the obtained magnetic shield was cooled in liquid nitrogen, a DC magnetic field was applied from the outside, and the magnetic shielding characteristics at the center of the tubular magnetic shield were measured using a Hall element. As a result, the internal magnetic flux density at the center of the tubular magnetic shield body exceeded 1 Gauss when the external magnetic flux density was 115 Gauss.

Example 2 As raw material powder, the molar ratio is Bi:Pb:Sr:Ca:C
Bi2O3, PbO, SrCO3, Ca so that u=1.92:0.48:2.0:2.0:3.2
After blending CO3 and CuO, adding ethanol and mixing with a resin mill and resin ball, drying, and calcining the obtained powder at 850°C for 50 hours, Bi1.8Pb0
．． A 2Sr2Ca2Cu3Oy oxide-based high-temperature superconducting powder was produced.

100g of this powder and PV as a binder
4g of B, 3g of DBP as a plasticizer, 1g of ethyl oleate as a dispersant and 5g of ethanol as a solvent.
0 ml and xylene 15 ml were mixed using a resin mill and a resin ball to prepare a slurry.

The obtained slurry was applied to a thickness of 1500 μm using a doctor blade device, and dried to a thickness of 100 μm.
A green sheet with a thickness of 0 μm was prepared.

[0025] The obtained green sheet has a diameter of 8 mm,
After winding it around a cylindrical alumina core with a length of 60 mm,
The sheets were bonded using hydrostatic pressure treatment at a pressure of 1500 kg/cm2, and the outer diameter was 45 mm, the inner diameter was 8 mm, and the length was 60 mm.
A tubular molded body of mm was obtained.

[0026] This molded body was heated to 500°C at a rate of 1°C/min in an air atmosphere, degreased, then fired at 850°C in an air atmosphere for 100 hours, and then allowed to cool in a furnace to determine its density. A tubular sintered body weighing 5.4 g/cm3 was produced.

Next, the obtained tubular sintered body was subjected to a pressure of 1500 k.
Hydrostatic pressure treatment was carried out at g/cm2 in atmospheric atmosphere.
Repeat baking at 50℃ for 50 hours twice,
Outer diameter 40mm, inner diameter 10mm, length 50mm, density 6.
A tubular magnetic shield of 1 g/cm3 was obtained.

While the obtained magnetic shield was cooled in liquid nitrogen, a direct current magnetic field was applied from the outside, and the magnetic shielding characteristics at the center of the tubular magnetic shield were measured using a Hall element. As a result, the internal magnetic flux density at the center of the tubular magnetic shield body exceeded 1 Gauss when the external magnetic flux density was 200 Gauss.

Comparative Example 1 As raw material powder, Bi:Pb:Sr:Ca:C in molar ratio
Bi2O3, PbO, SrCO3, C so that u=1.92:0.48:2.0:2.0:3.2
Blend aCO3 and CuO, mix with ethanol in a resin mill and resin ball, and then dry the powder.85
Calcined at 0℃ for 50 hours, Bi1.8Pb0.2Sr2C
A2Cu3Oy oxide-based high-temperature superconducting powder was produced.

[0030] This powder was press-molded at a molding pressure of 350 kg/cm2, and subjected to isostatic pressure treatment at a pressure of 1500 kg/cm2, resulting in an outer diameter of 40 mm, an inner diameter of 10 mm, and a length of 50 m.
A tubular molded body of m was obtained. This molded body is placed in the atmosphere.
After firing at 850° C. for 100 hours, it was allowed to cool in a firing furnace to obtain a magnetic shield body with a density of 4.5 g/cm 3 . With the obtained magnetic shield body cooled in liquid nitrogen,
A DC magnetic field was applied from the outside, and the magnetic shielding characteristics at the center of the tubular magnetic shielding body were measured using a Hall element. As a result, the internal magnetic flux density at the center of the tubular magnetic shield body exceeded 1 Gauss when the external magnetic flux density was 40 Gauss.

[0031]

[Effects of the Invention] According to the method of the present invention, by subjecting a sintered body of an oxide-based high-temperature superconducting material to hydrostatic pressure treatment and firing it again, it is possible to shield high density and high magnetic fields. This makes it possible to create a magnetic shielding material that can significantly expand the field of application of oxide-based superconductors.

Claims (1)

[Claims] 1. A method for manufacturing a magnetic shielding body, which comprises subjecting a sintered body of an oxide-based high-temperature superconducting material to hydrostatic pressure treatment and then firing it again.