JPH02299295A - Superconductive magnetic shield plate - Google Patents

Abstract

PURPOSE:To obtain a superconductive magnetic shield plate which is able to shield an object from intensive magnetism by a method wherein the magnetic shield plate is formed into a two-layered structure composed of a superconductive layer and a board which supports the superconductive layer. CONSTITUTION:A superconductive magnetic shield plate of this design is composed of a board and a superconductive layer, and it is desirable that a protective layer provided outside the superconductive layer and moreover an intermediate layer provided between the board and the superconductive layer are added. In this case, it is desirable that the materials of the board and the superconductive layer are so selected as to make the thermal expansion coefficient of the board nearly identical to that of the superconductive layer, the superconductive layer is not required to be defined in kind, and any kind of a board which has a prescribed thermal expansion coefficient can be used for this purpose, and the board can be formed of various kinds of material such as metal material, ceramic material, and glass material. By this setup, a superconductive magnetic shield plate, which has such a shielding capacity that it can shields an object from an intensive magnetic field, can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a superconducting magnetic shield plate, and more specifically,
The present invention relates to a superconducting magnetic shield plate that can be suitably used to shield strong magnetism from linear motors and the like.

[Prior Art] In recent years, nuclear magnetic resonance computed tomography diagnostic equipment (MRI) has been developed using superconducting magnets made of superconducting materials with superconducting properties.
ncc! (waging), magnetic levitation trains, etc. are being put into practical use. Furthermore, in the future, the application of the strong magnetic field of superconducting magnets is being considered for new energy development such as nuclear fusion and new energy conversion technologies such as MHD power generation.

When devices using superconducting magnets, such as MRI diagnostic devices, are used in this way, a leakage magnetic field is generated from these devices, which may have an adverse effect on the outside, which poses a problem.

Therefore, in order to solve the above-mentioned problems, a magnetic shielding material for shielding magnetism from a magnetic source is required.

[Problem to be solved by the invention] Conventionally, soft magnetic materials with high magnetic permeability and low coercive force have been used as magnetic shielding materials, or when shielding a large magnetic field, the shielding ability is too low and leakage occurs. There was a risk of generating a magnetic field. For this reason, although it is possible to increase the volume of the shielding material and increase the shielding effect, it is inevitable that the weight of the shielding material will increase.
There is a problem.

[Means for Solving the Problems] Therefore, as a result of intensive studies to solve the problems of the conventional magnetic shielding materials described above, the present inventors have developed a magnetic shielding plate having a two-layer structure having at least a superconducting layer and a substrate. The inventors have discovered that this method is effective, and have arrived at the present invention.

That is, according to the present invention, there is provided a superconducting magnetic shield plate characterized by having a two-layer structure including at least a superconducting layer and a substrate.

In addition, in the present invention, in the superconducting magnetic shield plate having a two-layer structure, if an intermediate layer is provided between the superconducting layer and the substrate to form a three-layer structure, the criticality, which is a superconducting property, This is preferable because the current density is improved.

Furthermore, the above two-layer or three-layer structure superconducting magnetic seal I
- It is preferable to use a superconducting magnetic shield plate with a three-layer structure or a four-layer structure in which a protective layer for protecting the superconducting layer is provided on the outside of the superconducting layer of the plate, since thermal shock resistance is improved.

[Function] The present invention is a ta conductive magnetic shield plate for appropriately shielding magnetism from magnetic sources such as leakage magnetism and terrestrial magnetism, and has a two-layer structure of a superconducting layer having superconducting properties and a substrate supporting it. It basically consists of:

Further, from the viewpoint of improving superconducting properties or thermal shock resistance, it is also preferable to have a three-layer structure having an intermediate layer or a protective layer, or a four-layer structure having a protective layer and an intermediate layer.

In the superconducting magnetic Sea Belt plate of the present invention, it is preferable to select materials for the substrate and the superconducting layer so that the coefficient of thermal expansion of the substrate is approximately equal to that of the superconducting layer. Similarly, in the case of a three-layer structure with an intermediate layer or a protective layer, the materials of the substrate, intermediate layer, and superconducting layer are selected so that the coefficient of thermal expansion of the intermediate layer and substrate is approximately equal to that of the superconducting layer. In the case of a four-layer structure having a protective layer and an intermediate layer, the substrate, intermediate layer, and superconducting layer are selected so that the thermal expansion coefficient of the intermediate layer and the substrate is approximately equal to that of the superconducting layer. It is preferable to select the material of

It is preferable to maintain the thermal expansion coefficients of the substrate and each layer used in this way in the predetermined relationship described above.Here, approximately equivalent to the thermal expansion coefficient of the superconducting layer means, specifically, the 811 tensile coefficient of the superconducting layer. for the value of.

This refers to a range of approximately ±5xlO-6/''C.

The type of superconducting layer used in the present invention is not particularly limited, and examples thereof include B1-5r-Ca-Cu-0 system, Y-Ba-Cu-0 system, etc.
-5r-Ca-Cu-0 system, Bi25r2Ca
Those having a crystal phase with a composition of Cu2On, Y-Ba-C
YBa for u-0 series.

Cu:IO, Ino! The crystal phase of 1JJk is used.

Moreover, if the thickness of the superconducting layer is too thin, the superconducting current will be small and the magnetic shielding ability will be low, and if it is too thick, the adhesion with the substrate will deteriorate.

Specifically, the thickness of the superconducting layer is approximately 0.2 m layer to 2 m
■It is considered to be moderate.

The substrate may be any material as long as it has a predetermined coefficient of thermal expansion as described above.Various materials such as metal materials, ceramic materials, or glass materials can be used. Specifically, metal materials such as iron, titanium,
Examples include beryllium, di-Sikel, and stainless steel. In addition, ceramic materials such as spinel, ajimina, zirconia (partially stabilized zirconia and stabilized zirconia), and magnesia τ, and glass materials such as various types of tying: f
As a protective layer for protecting the conductive layer, any material with excellent thermal shock resistance (or cold resistance) may be used, including metal materials, ceramic materials, and glass materials. Alternatively, various materials such as organic materials can be used.

Next, in the case of a three-layer or four-layer structure, the intermediate layer C provided between the substrate and the superconducting layer can be made of various materials such as metal materials, ceramic materials, or glass materials. Examples of the metal material include platinum, nickel, and V. Examples of the ceramic material include zirconia, and examples of the glass material include various crystallized glasses.

This intermediate layer preferably has no reactivity with the superconducting layer. If an intermediate layer that is reactive with the superconducting layer is used, it has a two-layer structure, with the reactive intermediate layer facing the substrate and the reactive intermediate layer facing the substrate. The intermediate layer that is not included is considered to be the superconducting layer side.

When it is difficult to directly adhere the superconducting layer and the substrate, a magnetic shielding plate with higher performance can be produced by selecting an intermediate layer with good adhesion to both the substrate and the superconducting layer.

The present invention provides a substrate as described above, a superconducting layer, preferably a
It is composed of a protective layer provided outside the S conductive layer, and more preferably an intermediate layer provided between the substrate and the superconducting layer,
This is a magnetic shield plate formed into a flat plate.

In a magnetic shielding plate having such a structure, its area is determined by the total length L (cm) of the circumference of the magnetic shielding plate in order to reduce magnetic leakage from the joints when combining large-area magnetic shielding panels. It is desirable that the ratio L/S of and area S (am") be less than 0.4 cm-".

Further, the shape is preferably a regular hexagon or a square, which allows the area to be increased without creating a gap when large-area magnetic shield panels are combined. In particular, regular hexagons and squares have a small L/S value when compared with the same area, and can reduce magnetic leakage.

In addition, the magnetic shield plate of the present invention has, at its end,
If the superconducting layer does not cover the entire substrate up to the edge, but the edge of the superconducting layer is made shorter than the edge of the substrate by about 1- or more, and the area of the substrate is larger than the area of the superconducting layer, This is desirable because peeling off and crack formation at the ends of the superconducting layer are suppressed.

Next, an example of a method for manufacturing a magnetic shield plate according to the present invention will be explained.

On the surface of a regular hexagonal or square substrate, the main component of the crystalline phase has a conductive property, for example, B1-5r-Ca-C.
A superconducting layer made of a u-0 system is applied by a spray method and then dried. Next, the firing conditions are different depending on the type of substrate or the type of each layer.
By firing at a temperature in the range of 0''C to 950'C for about 0.5 to 20 hours, a magnetic shield plate for unexploded use is manufactured.

The preferred embodiments of the present invention described above are summarized as follows.

(a) Superconducting magnetic shield plate 6 with an intermediate layer provided between the superconducting layer and the substrate (h) H1 conducting magnetic shield with a protective layer provided on the magnetic source side outside the superconducting layer to protect the superconducting layer Board.

(c) A protective layer for protecting the superconducting layer is provided on the magnetic source side outside the superconducting layer, and an intermediate layer is provided between the leading layer B and the substrate. .

(Se1) A superconducting magnetic shield plate whose engraving coefficient is approximately the same as the 8WI tensile coefficient of the superconducting layer.

(c) The thermal expansion coefficient of the intermediate layer and the substrate, or the heat of the superconducting layer (
A superconducting magnetic shield plate with approximately the same V as 7-4.

(f) ,! ! A superconducting magnetic shield plate whose area is larger than the area of the plate or the area of the Mi conductive layer.

(g) Total circumferential length L (c+s) of conductive layer a and surface I
A superconducting magnetic shield plate having a ratio L/S of Is (0 m2) of less than 0.4 cm-''.

[Example] (Examples 1 to 6 and Comparative Examples 1 to 4) - The main component of the crystal phase is 1li2sr2cacu on the surface of various square metal plates with side lengths of 1201 and thickness of 1 mm.
*After drying the powder of 011-Y by spraying, the thickness is about 0.1 to 4 tays, and the length of the - side is 100 to 120.
The main component of the crystalline phase, Bi, is coated on the metal substrate by 0 to 1 mm shorter than the edge of the substrate, and after drying, it is fired at a temperature of 900°C for 0.5 hours. 5r2C
aCu, 0. −.

A metal plate on which a superconducting ceramic layer was formed was obtained.

The substrate metals were various materials ranging from copper with a thermal coefficient of 4.7Xl0-'/'C to copper with a thermal coefficient of 19.7X10-'/'C.

As a result, as shown in Table 1, the coefficient of thermal expansion was 4.7xl.
Peeling occurred in o-6/'C Kovar, 8,9X10
Good adhesion with the substrate was achieved with titanium at -6X°C and nickel at 13.3X 10-'/'C.
x 10-'/'C 5US304 stainless steel and 19.
With copper at 7x 10-6/'C, delamination occurred again.

Further, as shown in Table 1, it was confirmed that the metal plate in which the superconducting ceramic layer had a good adhesion state had a magnetic shielding ability of 5 Gauss or more.

Furthermore, it was confirmed that at the end of the shield plate, if the distance from the end of the substrate to the end of the superconducting layer was less than 1 ms+, the ceramic layer would peel off from the substrate.

(Hereinafter, blank spaces) (Examples 7 to 11 and Comparative Examples 5 to 6) - The main component of the crystal phase was YBa on the surface of various square ceramic plates with a side length of 120 i++s and a thickness of 5 I 1 m.
Powder of 2C11107-Y was applied by spraying to a thickness of about 1 mm after drying, with the side length 51 mm shorter than the edge of the substrate, and then dried at a temperature of 950°C for 10 hours. By firing under the firing conditions, a ceramic plate was obtained in which a superconducting ceramic layer having a main crystalline phase of YBa2Cu:507-y was formed on a ceramic substrate.

The coefficient of thermal expansion of the ceramic substrate is 4.2 x 10-'/
Various materials were used, ranging from zircon with a value of 1.5 x 10-'/'C to manesia with a value of 1.5 x 10-'/'C.

As a result, as shown in Table 2, the thermal expansion coefficient was 4.2×lO
``6/℃ zircon causes peeling 8.8X to-'
/'C alumina to 13.5X 10-6/'C'
? It was confirmed that 'Gune 1/7 achieved good adhesion with the substrate and had a magnetic shielding ability exceeding a predetermined level.

(Examples 12 to 14) - The main component of a crystal layer was formed on the surface of various square glass plates with a side length of 120 mm and a thickness of 5 cm. Sr, CaC
Apply U20O-Y powder by spraying to a thickness of approximately f■ after drying, 5cm shorter than the edge of the substrate so that the length of the - side is 110cm, and after drying, apply at 900℃ to 0. After firing under the firing conditions for .5 hours, the main component of the crystal phase, Bi25r2CaCu20. A glass plate on which a superconducting ceramic layer was formed was obtained.

The thermal expansion coefficient of the substrate glass is 13.5X 10-'/”C
It was made into a crystallized glass of 17.5x 10-'/'C.

As a result, as shown in Table 3, tfl
It was confirmed that good adhesion with the conductive ceramic layer was achieved and that it had a magnetic shielding ability of 5 Gauss or more.

(Hereinafter, blank spaces) (Examples 15 to 1B) In the metal plate on which the superconducting ceramic layer formed in Example 1 was formed, a protective layer was further provided on the surface of the superconducting ceramic layer, and the metal plate was placed in liquid nitrogen. Thermal shock resistance was evaluated when exposed to heat.

For the protective layer, we selected aluminum metal and cold-resistant synthetic resin.

As a result, as shown in Table 4, both of the lI layers exhibited better thermal shock resistance than Ceraminx in the drop test into liquid nitrogen.

(The following is a margin) Table 4 (Examples 19 to 23) Calcia-stabilized zirconia, platinum, nickel and I! gO・B20 Yu・Sin
.

Approximately 200 g of glass is formed, and superconducting ceramic is formed on the intermediate layer, the main component of the crystal phase being old 2Sr2.
CaCu206-y powder was applied by spraying to a thickness of about 1 layer after drying, 5 layers shorter than the edge of the substrate so that the side length was 110 m5, and after drying it was heated at 900°C. Firing was performed under the firing conditions for 0.5 hours to obtain a metal plate in which a superconducting ceramic layer having a crystalline phase as a main component of Bi25r2CaCu20a-y was formed on the metal substrate.

The substrate metals were titanium and nickel.

As a result, as shown in Table 5, good adhesion was achieved for all intermediate layers, and the critical current density, which is a characteristic of superconductivity in liquid nitrogen, was lower than that of Example 1 without an intermediate layer. Improved.

(Examples 23 to 27) In the metal plates on which the superconducting ceramic layers prepared in Examples 19 to 22 were formed, a protective layer was further provided on the surface of the superconducting ceramic layer, and the thermal shock resistance when dropped into liquid nitrogen. The gender was evaluated.

For the protective layer, aluminum metal and cold-resistant synthetic resin were selected.

As a result, as shown in Table 6, both protective layers exhibited better thermal shock resistance than the case without the protective layer in the drop test into liquid nitrogen.

(Hereinafter, blank spaces) (Examples 28 to 34, Comparative Example 7) A superconducting ceramic layer was formed on the surface of a square or regular hexagonal base material with a wall thickness of 1 m to 5 am and made of various materials having various scoribilities. The unit magnetic shield plates were combined to form a square magnetic shield panel with a side length of -1 or 1, and its magnetic shielding effect was confirmed.

As a result, as shown in Table 7, the ratio L/S of the total circumferential length L (c) of the magnetic shield plate to the surface 1s (cpeng 2) is 0.
．． When it was less than 4 cm-', the applied magnetic field was reduced to 1/10 or less, and it was confirmed that the magnetic field had sufficient magnetic shielding ability.

(Hereafter, blank space) Total length L (cm) of the circumference of the magnetic shield plate and area S (
When the relationship between the ratio L/S of am2) and the magnetic field ratio is shown in a graph,
As shown in FIG. 1, it can be seen that when L/S is less than 0.4 cm-', the applied magnetic field is reduced to 1710 or less, and there is sufficient magnetic shielding ability.

[Effects of the Invention] As explained above, the superconducting magnetic shield plate of the present invention not only can appropriately shield the magnetism from the intended magnetic source, but also has improved mechanical strength and excellent durability. , making it easier to handle the compost.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the ratio L/S of the circumferential length L (cm) and the area S (cm'') of the magnetic shield plate and the magnetic field ratio.

Claims (1)

[Claims] (1) A superconducting magnetic shield plate characterized by having a two-layer structure including at least a superconducting layer and a substrate.