JPH01282899A - Magnetic shield material using superconductive material - Google Patents

Abstract

PURPOSE:To use Fe-Cr-Al system alloy as a shield material and give full play to magnetic shield performance by combining a lightweight unbulky shield material and a cooling means in which mounting and operation can comparatively easily be performed and cost is low. CONSTITUTION:Power of superconductive material of R-Ba-Cu-O system or Bi-Sr-Ca-Cu-O system is melted and jetted in a base material with the shape of required magnetic shield material and heat treatment is performed. The alphabetical letter R shows one kind or two kinds and more selected from Y and La system rare earth elements. The heat treatment material is cooled at the boiling point of liquid nitrogen or the temperature less than it to use. Fe-Cr-Al system alloy is used as the material of a base material. The thin film of molten and jetted superconductive material is treated by heat and shows superconductivity. Thereby magnetic shield performance is fully shown.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to a shielding material for a magnetic shielding device using a superconducting material.

[Prior Art] The most common means of magnetic shielding is to prepare a shield in a desired shape using a soft magnetic material with high magnetic permeability, such as pure iron or permalloy. For example, 5QLJID (
As for the superconducting quantum interferometer) and the Josephson computer, walls of pure iron as thick as 2 meters are used to completely block out the influence of external magnetic fields, including the earth's magnetism.

In maglev trains, which are currently being developed, electromagnetic coils generate strong magnetic fields that affect passengers' electronic devices. Familiar electronic devices include digital clocks, laptop computers, and word processors, and special devices include cardiac pacemakers, and the former's malfunction is a life-threatening problem. Therefore, in order to put linear motor cars into practical use, it is necessary to establish effective magnetic shielding means. However, since a linear motor car is magnetically levitated and moves at high speed, the magnetic shielding device cannot be made excessively heavy.

Superconducting materials, which have attracted attention in recent years, are known to exhibit complete diamagnetic properties in the superconducting state.

In the above-mentioned high permeability soft magnetic material, magnetic shielding is performed by a mechanism in which the material itself absorbs magnetic flux. Therefore, when shielding against a strong magnetic field or when attempting to completely eliminate leakage of magnetic flux, a large amount of shielding material is required. On the other hand, superconducting materials do not allow magnetic flux to enter from the outside and reflect all of it, so even if they are relatively thin, they can be expected to have a high magnetic shielding effect of 1q. However, in order to perform magnetic shielding using the superconducting phenomenon, it goes without saying that it is necessary to cool the superconducting material below its critical temperature and maintain it in a superconducting state. We must consider the means as one.

Based on the above considerations, the inventors developed a magnetic shielding device that combines a lightweight shielding material made of superconducting material that does not become bulky, and a cooling means that is relatively easy to install and operate and is inexpensive. was invented and separately proposed. The device uses R-Ba-C as a shielding material.
1J-0 system or Bi-Sr-Ca-CI-
A thin film is formed by thermally spraying a 0-series high-temperature superconducting material onto a base material in the shape of a magnetic shielding material, and a cooling means capable of cooling the material to a temperature at or below the boiling point of liquid nitrogen is combined.

However, while manufacturing various magnetic shielding materials according to the present invention and measuring their shielding effects, it was discovered that some of them did not exhibit the expected performance.

(Problems to be Solved by the Invention) An object of the present invention is to provide a magnetic shielding material capable of solving the above-mentioned problems and fully exhibiting the magnetic shielding performance inherent to superconducting materials, and to solve the above-mentioned problems. The goal is to be able to completely receive the effects.

[Means for solving the problem] A magnetic shielding device using the superconducting material of the present invention has R
-Ba -C1J-0 series [R is one or more selected from Y and La rare earth elements, Ba
can be partially or completely replaced with Sr, and F can be included in this system. ] or Bi-Sr
-Ca -Cu -0-based high temperature superconducting material powder is melted into a base material having the shape of the required magnetic shielding material, heat treated to give it superconductivity, and the powder is heated to a temperature lower than the boiling point of liquid nitrogen or lower. A magnetic shielding material used after being cooled to a temperature is characterized in that a Fe-0r-1 alloy is used as a base material.

Fe-Cr-Au alloys useful as base materials for magnetic shielding materials contain 17 to 26% Cr and 2 to 6% L, with the remainder consisting essentially of C. Within this composition range, (17-21) Cr-(2-4) is commercially available in the form of heating wires.
1-Fe alloy, which is usually sufficient.

The thermal spraying is preferably plasma spraying, but gas spraying may also be used.

The thermally sprayed thin film of superconducting material becomes superconducting by heat-treating it by a known method.

[Function] As a base material for forming a thin film of superconducting material by thermal spraying,
Metal is suitable from the viewpoint of ease of molding and mechanical strength.

However, the superconducting material after thermal spraying does not become superconducting until it is heat treated. Heat treatment is, for example, 950°C
x 2 hours in an oxygen atmosphere.

The reason why superconducting materials do not perform as expected is thought to be that the base material is oxidized by this heat treatment, and the generated oxides affect the superconducting materials physically and chemically, causing them to change in quality. .

When Fe-Cr-A, 11-based alloy is used as a base material according to the present invention, this alloy can withstand oxidizing atmosphere even at high temperatures,
Only a very thin oxide film is created on the surface, and this film is extremely stable physically and chemically, so it does not have any adverse effect on the superconducting material sprayed onto the substrate. Therefore, the performance as a magnetic shielding material is not hindered.

(Example) Y203 powder (purity 99.99%, average particle size 1.5 μm
), BaCO3 powder (purity 99.9%, average particle size 1 μT
rL) and CuO powder (purity 99°9%, average particle size 1
μm) as raw material, Y203: BaO: by weight
Cu o=1.129: 3.386: 2.38
The ingredients were mixed in a mortar.

The mixture was placed in an alumina crucible and calcined in the air. The calcined material is crushed again and polyvinyl butyral resin (
1.1 m of liquid with a polymerization degree of 700) per 1 g of calcined powder
Add at the rate of
#X It was molded into a rod-shaped body with a length of 50 m and a thickness of 7 NII.

This was fired in the air at 950°C for 16 hours to obtain a black sintered body.

This sintered body has a superconducting critical temperature of 92 and 80K.
The magnetization in a magnetic field of 1000e is 4πI=-18G
Met. Since a perfect superconductor has 4πI=-100G, the amount of superconducting material contained in this sintered body is 18%.

Subsequently, the above sintered body was placed in a ball mill and pulverized to a particle size of 50 to 150 μm. This powder was passed through an rDEM filter, a device that separates ferromagnetic materials and diamagnetic materials (Daido Tokushu 14 ■ ¥A), to collect only the superconducting particles and concentrate them to more than 50%.

The concentrated powder was plasma sprayed to a thickness of 100 μm under the following spraying conditions to form a thin film of superconducting material.

Thermal spray gun: Metco 9MB (manufactured by Daiichi Metco) Gas:
Mixed gas of Ar (50,1!/hr)+-(7,9/hr) Current: 50OA Voltage near 5■ Thermal spraying distance: 150m The base material was 18Cr-3Δρ-Fe composition. A cylinder with a thickness of 0.5 m, an inner diameter of 50 #, and a length of 150 m was used.

After thermal spraying, this cylinder was placed in a furnace and heated at 950'CX for 2 hours.
It was heat treated in an oxygen atmosphere and cooled in a furnace.

A measuring device with the configuration shown in the figure was prepared. Dua-Bottle 2
The cylinder 1 sprayed with the above-mentioned superconducting material is placed in liquid nitrogen (not shown) inside the cylinder, the search coil 3 is placed inside the cylinder 1, and the electric signal from the transmitter Qsc is amplified by the amplifier A11). The magnetic shielding effect was examined by applying the voltage to the Helmholtz coil 4 and detecting the output of the search coil using a lock-in amplifier Ln-Amp.

The magnetic shielding effect Ems [dB] is one line defined by the following formula.

Ems [dB] = -201 og/e.

[In the formula, e□ is the search coil output (mV) when there is no shield, and e is the search coil output (mV) when it is shielded. ]

The measurement conditions are as follows.

Magnetic field strength: 1-1o = 1 [Oe] (e□ =
5.7 mV) Frequency: f = 50 [Hz] For comparison, a cylinder made of pure iron with the same dimensions as above was also made with a superconducting material sprayed on it, and the shielding effect was examined under the same conditions.

The results are as follows.

Shielding material Output e Shielding effect (μV) (dB) (Example) Fe-Cr-AN alloy 0.001 135 (Comparative example) Pure iron 0.010 115
Substantially the same results were obtained when the superconducting material was thermally sprayed by gas spraying under the following conditions.

Thermal spraying gun: Meticolo Pn type (same as above) Gasfu 02 + acetylene spraying distance: 150m Spraying thickness: 100μ'rrl (same as above) [Effects of the invention] According to the magnetic shielding material using the superconducting material of the present invention, The effects of the invention described above are that effective magnetic shielding can be achieved with a lightweight and small shielding material without using the conventional heavy and bulky shielding material made of high magnetic permeability material, and liquefied nitrogen is sufficient for cooling. It is easy to construct and operate, and can take full advantage of its low cost.

[Brief explanation of the drawing]

The drawing is a diagram conceptually showing an apparatus for testing the performance of the magnetic shielding material of the present invention. 1... Cylinder sprayed with superconducting material 2... Dual bottle 3... Search coil 4... Helmholtz coil Osc... Oscillator Amp... Amplifier Ln-Amp... Lock-in amplifier patent application Person Daido Steel Co., Ltd. Agent Patent Attorney Souo Suga Amρ

Claims (2)

[Claims] (1) R-Ba-Cu-O system [R is one or more selected from Y and La rare earth elements,
Ba can be partially or completely replaced with Sr,
Moreover, F can be included in this system. ] or Bi-S
Powder of r-Ca-Cu-O-based high-temperature superconducting material is thermally sprayed onto a base material having the shape of the required magnetic shielding material, and heat-treated to give it superconductivity. In magnetic shielding materials using superconducting materials that are cooled to low temperatures, Fe is used as the base material.
- A magnetic shielding material characterized by using a Cr-Al alloy. (2) As the material of the base material, Cr: 17-26% and A
2. The magnetic shielding material according to claim 1, comprising an alloy containing 2 to 6% of L, with the remainder substantially consisting of Fe.