JPH05283881A - Superconductive magnetic shield container and its manufacture - Google Patents

Abstract

PURPOSE:To prevent exforiation from a base material by expansion of a high Tc phase or the drop of density and improve the critical current density of the high Tc phase by putting this container in laminate structure wherein the high-temperature phases and the low-temperature phases of bismuth oxide superconductors are stacked alternately after forming a base as occasion demands on the base material. CONSTITUTION:A film of Ag or the like is made as an undercoating material 2, on the periphery of a base material 1 such as an Ni allay cylinder, etc. Next, a low Tc-phase film 3 is made, and then a high Tc-phase film 4 is made, and the low Tc-phase film 3 formation and the high Tc-phase film formation are performed repeatedly, and a low Tc-phase film 3 is stacked at the outermost layer so as to manufacture a film. It is preferable that the low Tc-phase film 3 should be made right on an undercoating material 2 such as Ag, etc., made as desired on the base material 1 and that the low Tc-phase film 3 made also at the outermost layer. Since the high Tc-phase film is sandwiched by the low Tc-phase films, the expansion of the high Tc-phase at heat treatment is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting magnetic shield container in which a high Tc phase coating and a low Tc phase coating of a Bi-based oxide superconductor having a critical temperature of 77K or higher are laminated on a base material and a container thereof. It relates to a manufacturing method.

[0002]

2. Description of the Related Art Generally, it is well known that magnetic shields include active shields and passive shields, and passive shields include ferromagnetic shields and superconducting shields. , Each magnetic shield has its own characteristics (Ogasawara “Cryogenics” Vol. 8.No.4,197)
3. See P135-147). Among these magnetic shields, the ferromagnetic shield takes in an external magnetic field with a ferromagnetic material, for example, permalloy, so that the magnetic field does not enter the internal space, whereas the superconducting shield does not take the external magnetic field into the superconductor. , By excluding it toward the outside, it prevents the magnetic field from penetrating into the internal space, and the magnetic shield effect is orders of magnitude greater than that of a ferromagnetic material. That is, the ferromagnetic shield has a limit due to the presence of residual magnetization, and the magnetic shield in a region exceeding this limit must wait for the superconducting magnetic shield. However, for example, in a Nb-based metal-based superconductor, since liquid helium needs to be used as a coolant, there is a cost barrier in the magnetic shield construction,
The superconducting shield has not been put to practical use except for a part.

However, the magnetic shield container of an oxide superconductor has a great merit because it can be used at the temperature of liquid nitrogen, and has been attracting attention. For example, when a large magnetic shield body such as a biomagnetism measurement or a magnetic shield of an electron beam exposure apparatus is made of an oxide superconductor, it is advantageous to make the superconducting layer thick on the base material.

On the other hand, the thermal spraying method, particularly the plasma spraying method, is Bi
It is widely used by a simple method to form a film of oxides and ceramics. Generally, these Bi-based oxides have a high Tc phase of about 100K and a low Tc of about 90K.
A phase is formed. When a high Tc phase coating of Bi-based oxide is formed by the conventional plasma spraying method, superconducting properties are obtained by crystallization by heat treatment after thermal spraying. At that time, the high Tc phase coating has a volume during the crystallization process. It causes swelling, easily peels from the substrate, and the density is remarkably reduced. It has been recognized that this decrease in density is likely to cause fine cracks due to heat shock due to heat cycle and a slight impact force, so that the magnetic shield effect tends to be significantly decreased. Conventionally,
In order to increase the critical current density Jc in the crystallization process and prevent density decrease due to swelling in the heat treatment process after thermal spraying, a process of performing a heat treatment again by applying a load perpendicular to the film surface has been performed. In this process, if the shape of the shield container becomes large and complicated, the cost increases, which is a major obstacle to practical use. However, with a coating containing only a low Tc phase, Tc and Jc are not sufficient although there is no swelling in the heat treatment process after thermal spraying, and there is no temperature margin during indirect cooling with liquid nitrogen, making it difficult to design the cryostat.

The present invention has a high Tc in the heat treatment process after thermal spraying.
(EN) A magnetic shield container capable of preventing peeling from a base material and a decrease in density due to phase swelling, thereby improving the critical current density Jc of a high Tc phase, and increasing the size of the magnetic shield container, and a manufacturing method thereof. The purpose is to

[0006]

According to the present invention, an underlayer is formed on a base material if necessary, and then a high Tc phase and a low Tc phase of a bismuth oxide superconductor are alternately laminated by a thermal spraying method. The above-mentioned problems are solved by using such a laminated structure.

In the present invention as described above, the low Tc phase contains Pb or Ag, or 0.01 to 0.01% of both elements.
It may contain 0.3 molar ratio. For example, the low Tc phase is Bi: Sr: Ca: Cu = 2: 2: 1: 2 (221
It is represented by the composition ratio of 2). For example, Pb is compounded in this composition, and Bi: Pb: Sr: Ca: Cu = 2: 0.
It can be 2: 2: 1: 2. The heat treatment temperature for expressing the low Tc phase by complexing in this way is from the normal 870 ° C. to the high Tc phase expression temperature.
It can be lowered to 0 ° C. High Tc formed
Both the phase and low Tc phase films can exhibit superconducting properties by heat treatment at the same temperature. Further, by adding the above-mentioned element, for example, the partial melting temperature of the low Tc phase is increased to 850 ° C.
Can be reduced to In this case, for example, after the film is formed, it can be heat-treated at a temperature at which the low Tc phase partially melts, for a short time, and then at a temperature at which the high Tc phase exhibits superconducting properties, for example, at 830 to 840 ° C. By performing such a heat treatment, the sprayed low Tc phase coating is partially melted and the high Tc phase coating is sandwiched, and the high Tc phase coating is prevented from peeling from the base material and swelling is prevented. Densification can be promoted.

The present invention will be described below with reference to the accompanying drawings. FIG. 1 shows an example of a multi-layer structure according to the present invention. In the figure, 1 is a base material such as a cylinder of Ni-based alloy, and an undercoating material 2 is provided on the outer periphery of the base material 1.
As a coating, a film of Ag or the like is formed in a thickness of 50 to 100 μm. Next, after forming a low Tc phase coating 3 of about 50 μm, a high Tc phase coating 4 of about 100 μm was formed, and the low Tc phase coating 3 and the high Tc phase coating 4 were repeated 3 times, and the low Tc was formed on the outermost layer. The phase coating 3 was laminated in a thickness of about 50 μm to form a coating having a total thickness of about 500 μm.

As shown in FIG. 1, preferably, a low Tc phase film 3 is formed on a base material 1 directly on an undercoating material 2 such as Ag, which is optionally formed, and a low Tc is also formed on the uppermost layer. The phase film 3 is formed.

[0010]

According to the present invention, a high Tc phase film has a low Tc.
Since it is sandwiched by the phase coating, the swelling of the high Tc phase during heat treatment is prevented, and the density reduction prevention effect of the low Tc phase coating prevents the density reduction of the thermal spray coating as a whole. Cracking is prevented, the magnetic shield effect is improved, and peeling from the base material is also prevented. Therefore, a large magnetic shield container using liquid helium as a refrigerant can be obtained.

Examples will be shown below.

[0012]

EXAMPLE 1 High Tc phase and the low-Tc phase of Bi-based oxide with _{Bi 2 O 3, SrCO 3,} CaCO 3 and CuO raw material, the high Tc phase is _{Bi 1. 5 Pb 0. 5} Sr 1. ₉ Ca _{1. 9} Cu _2.
8 Oy composition (hereinafter, abbreviated to 1.5-0.5-1.9-1.
Mixed and to be 9-2.8) The low Tc phase _{Bi 2 Pb 0. 2 Sr 2} Ca 1 Cu 2 Ox ( hereinafter generally, 2-0.
2-2-1-2) and mix each to 80
After pre-sintering at 0 ° C. × 10 h and main sintering at 840 ° C. × 100 h, the powder was pulverized to have a particle size of 50 to 100 μm. Using such particles, a cylinder of Inconel 625 having an outer diameter of 100 mm (thickness of 1.6 mm) and a length of 500 mm was subjected to the thermal spraying conditions and the thermal spraying process as described below.

2-0.2-2-1-2 particles and 1.5
-0.5-1.9-1.9-2.8 Particles are sprayed under the condition that the torch operation output is about 11 kW (80A × 135V), air is used as the working gas, plasma jet is generated, and each particle is generated. It was fed at a position of 90 mm. Plasma separation (P-SEP) gas flow rate 25 l / m
In, the above Inconel cylinder was placed at a distance of 115 mm from the starting point of arc generation, and a Bi-based oxide film was attached. FIG. 2 shows a schematic diagram of the thermal spraying method. An Ag coating was previously formed as an undercoating material on the Inconel cylinder. The spraying condition is that the torch actuation output is about 1
3KW (110A × 118V), using Angol as working gas, plasma jet is generated to generate Ag particles of 5
It is fed at the position of 0 mm and the flow rate of P-SEP gas is 451 /
min, and the Ag-based film was deposited on the above Inconel cylinder at a distance of 115 mm from the arc generation starting point to about 100 μm. As other conditions, plasma spraying was performed in the atmosphere, and the Inconel cylinder was rotated at a rotation speed of 120 rpm and a feed speed of 13.8 mm / sec.

The thermal spraying procedure is as follows. First, the surface of the Inconel cylinder is roughened with Al ₂ O ₃ particles, then Ag particles are applied, and then the low T
After coating the c-phase 2-0.2-2-1-2 particles with a thickness of about 50 μm, the high Tc phase with a thickness of about 100 μm was sprayed by repeating three times, and the low Tc phase of the outermost layer was treated with about 100 μm. A total of about 500 μm was obtained by wearing 50 μm. Immediately after thermal spraying, the film is amorphous and close to an insulator.
After heat treatment for h, slow cooling of 60 ° C./h was added to room temperature. Critical temperature Tc (resistance = O) of the produced laminated film
Is 105K, the critical current density Jc is 77K,
In the magnetic field H = O, a magnetic shielding effect of about 800 A / cm ² and a magnetic shielding property of an external magnetic field of 1 gauss and 1 / 1,000,000 was obtained.

[0015]

Example 2 Using the same thermal spraying method as in Example 1, high Tc was obtained.
A layered structure film of the phase and the low Tc phase was prepared. 8 this film
Partially melt at 50 ° C for 10 minutes, then 840 ° C x 15
It was heat-treated for 0 hours and gradually cooled in the same manner as in Example 1. The produced film has Tc of 100K, Jc of 77K, and H = O.
Of about 500 A / cm ² , and the magnetic shielding characteristic was 1 millionth of a magnetic shielding effect with an external magnetic field of 1 gauss.

[0016]

Example 3 Using the same thermal spraying method as in Example 1, high T
A laminated structure film of c phase and low Tc phase was prepared. Note that Bi
Bi ₂ Ag ₀ is low Tc phase composition of the system oxide containing Ag. ₂ Sr
₂ CaCu ₂ Ox was used. Then, the same heat treatment was performed. The prepared laminated film has a critical temperature Tc (resistance = O) of 101 K, a critical current density Jc of 77 K, a magnetic field H = O of about 700 A / cm ² , and a magnetic shield characteristic of 1 G per million. The magnetic shielding effect of was obtained.

[0017]

[Comparative Example] Under the same thermal spraying conditions as in Example 1, a high Tc phase single layer was sprayed onto an Inconel substrate (width: 0.5 cm, length: 2 cm strip) undercoated with Ag. When this film was heat-treated at 840 ° C. for 150 hours, the high Tc phase film was completely peeled from the base material in four of the five test pieces, and a superconducting film could be formed on the base material. There wasn't. The remaining Tc is 100K and Jc is 10A.
Was / cm ² . Next, as in Example 1, when a high Tc single layer coating was sprayed on an Inconel cylinder undercoated with Ag and heat treated in the same manner, the coating was completely peeled off from the base material, and a magnetic shield container was produced. could not.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing an example of a multilayer structure of a film according to the present invention.

FIG. 2 is a schematic diagram of a thermal spraying method according to the present invention.

[Explanation of symbols] 1 base material 2 undercoating material 3 low Tc phase coating 4 high Tc phase coating

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Hirofumi Odaka 1-3-1-114 Haraki, Ichikawa City, Chiba Prefecture (72) Inventor Kazuhiko Kato 708, Kumagaya City, Saitama Prefecture (72) Inventor Kazutomo Hoshino Ageo, Saitama Prefecture 441-19 Otanihongo, Ichi, Japan (72) Yuji Yoshida, Inventor Yuji Yoshida, 1-12-1 Sengen, Tsukuba, Ibaraki Prefectural Institute for Metals Technology, Tsukuba Branch (72) Inventor, Michiya Yuyama 2-1-1, Institute of Metals and Materials Research, Science and Technology Agency Tsukuba Branch (72) Inventor Ren 2-1-1, Sengen, Gengen, Tsukuba, Ibaraki Prefectural Institute of Metals and Materials Research, Science and Technology Agency, Tsukuba Branch (72) Inventor Hiroshi Maeda 1-12-1 Sengen, Tsukuba-shi, Ibaraki, Tsukuba Branch, Institute for Metals Technology, Science and Technology Agency (72) Inventor Yutaka Kamegawa 13-13-6, Minamikyugahara, Ota-ku, Tokyo Company Japan Keiki Seisakusho (72) Inventor Masayuki Suzuki 1-13-6 Minamikyugahara, Ota-ku, Tokyo Stock company Nihon Keiki Seisakusho (72) Inventor Kiyoshi Nakayama 1-13-6 Minamikyugahara, Ota-ku, Tokyo (72) Inventor Teruo Shimizu 1-13-6 Minamikyugahara, Ota-ku, Tokyo Incorporated Nippon Keiki Co., Ltd.

Claims (3)

[Claims] 1. A basic composition of a low Tc phase (80K phase) and a high Tc phase (110K phase) of a bismuth-based oxide superconductor is formed by a thermal spraying method after an underlayer is formed on a substrate as required. A method for manufacturing a superconducting magnetic shield container, characterized in that the superconducting coatings are alternately laminated. 2. The composition of the low Tc phase is 0.01 to 0.3.
The method according to claim 1, comprising one or two elements of Pb and Ag in a molar ratio. 3. An undercoat layer optionally formed on a substrate, and a low Tc phase (80K phase) sprayed layer and a high Tc phase (110K phase) sprayed layer of a bismuth oxide superconductor formed thereon. A superconducting magnetic shield container in which and are alternately stacked.