JPH0218306A - Starting material for superconductor - Google Patents

Abstract

PURPOSE:To store particulate matter of starting materials for a superconductor for over a long time while inhibiting deterioration of the quality due to atmospheric oxygen or moisture by covering the particulate matter with a covering material. CONSTITUTION:After calcining a primarily pulverized mixture of particulate starting materials for a superconductor, the product is sintered after secondary pulverization and mixing, to obtain thus a particulate matter of the superconducting material contg. Y or Bi. Then, the particulate matter is fed together with a covering material (e.g. fluoroplastic) to a treating chamber 3 of a bottomed cylindrical casing 4 revolved at high speed from a feeder 19 through a passage 6 with a transporting gas supplied by a fan 18. Thus, the particulate matter is covered by the covering material and pressed by a centrifugal force to an internal peripheral surface of the casing. Then, the particulate matter is pulverized by grinding pieces 9a by rotating the grinding pieces and scraping pieces 9b relatively with a fixed relative velocity difference against the casing 4 around a rotary shaft 8a interlocked to a driving device 5. The pulverized product is mixed simultaneously by stirring with the scraping pieces 9b, then conveyed pneumatically to a collector 15 from an overflow type discharging port 11 through a passage 10, and recovered.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a powdery superconductor raw material.

[Conventional technology]

Conventionally, there has been no coating applied to powdery superconductor raw materials.

[Problem to be solved by the invention]

However, if powdered superconductor raw materials are stored for a long period of time, they suffer from deterioration in quality due to atmospheric oxygen and moisture.

It is an object of the present invention to enable powder-like superconductor raw materials to be stored for a long period of time in a state where quality deterioration due to oxygen and moisture in the atmosphere is sufficiently suppressed, and furthermore, to provide a means for this purpose for use in superconductor products. The point is to make it advantageous in terms of manufacturing.

[Means to solve the problem]

The characteristic configuration of the first invention is that the granular material of the superconducting material is covered with a coating material, and the effect thereof is as follows.

[For production]

In other words, by eliminating or sufficiently suppressing the contact between the superconducting material powder and the atmosphere using the coating material, it is possible to sufficiently suppress the quality deterioration of the superconducting material powder and granules due to oxygen and moisture in the atmosphere. Good long-term storage of raw materials becomes possible.

[Means to solve the problem]

The characteristic configuration of the second invention is that the granular material of the superconducting material containing Y is covered with a coating material having a melting point of 450° C. or lower, and its action is as follows.

[For production]

That is, as in the first invention, the action of the coating material can sufficiently suppress the deterioration of the quality of the superconducting material powder due to oxygen, moisture, etc. in the atmosphere, and the superconducting raw material can be stored for a good long term.

Furthermore, since the melting point of the coating material is 450° C. or lower, the superconductivity of the superconducting material is not impaired due to heating and melting treatment of the coating material when sending the superconducting product.

In other words, superconducting materials containing Y have an orthorhombic crystal structure and exhibit superconductivity, but when they become tetragonal, they lose superconductivity.
In addition, when heated above about 550°C, the crystal structure changes from orthorhombic to tetragonal, and if the melting point of the coating material exceeds 450°C, the heating and melting process of the coating material will be carried out efficiently. Therefore, when a high-temperature heat source of about 550° C. or higher is used, there is a large risk that the superconducting material will be heated to about 550° C. or higher and lose superconductivity due to a change in crystal structure.

However, if a coating material with a melting point of 450°C or less is used as in the second invention, the coating material can be efficiently heated and melted using a low-temperature heat source at a rate of less than about 550°C. Structural changes can be reliably prevented and good superconductivity can be reliably maintained.

[Means for Solving the Problems] The characteristic configuration of the third invention is that the granular material of the superconducting material containing Bi is covered with a coating material having a melting point of 800°C or less, and its effect is as follows. That's right.

[For production]

That is, as in the first invention, the action of the coating material suppresses deterioration of the quality of the superconducting material powder due to atmospheric oxygen, moisture, etc., and enables good long-term storage of the superconducting raw material.

In addition, superconducting materials containing Bi exhibit good superconductivity as long as they do not melt at temperatures above about 890°C, so their melting point is 890°C or higher.
If a coating material having a temperature of 00° C. or lower is used, the coating material can be efficiently heated and melted, and good superconductivity can be reliably maintained for the same reason as in the second invention.

〔Effect of the invention〕

As a result, it has become possible to provide a much superior superconductor raw material that has excellent storage stability and is advantageous in the production of superconductor products.

〔Example〕

Next, examples will be shown.

As shown in Figure 1, each powdery raw material for the superconductor is weighed, the weighed powdery raw materials are subjected to primary pulverization and mixing treatment using a dry grinding mixer, and the fine powdery raw materials obtained through the secondary pulverization and mixing treatment are The granular raw material obtained through the calcination treatment is subjected to secondary pulverization and mixing treatment using a dry grinding and mixing device, and the fine powdered raw material obtained through the secondary pulverization and mixing treatment is subjected to a sintering treatment to add Y or Bi. Make powder and granules of superconducting material containing

Calcination treatment is generally performed by heating at about 400°C for about 2 hours, then heating at about 900°C for about 4 hours for superconducting materials containing Y, and heating at about 800°C for about 16 hours for superconducting materials containing Bi. .

For superconducting materials containing Y, the sintering process is generally performed at a temperature of 900 to 9
After heating at about 30° C. for about 12 hours, it is slowly cooled at about 100° C./hr, then heated at about 520° C. for about 5 hours, and then slowly cooled at about 100° C./hr. Moreover, in the case of a superconducting material containing Bi, the material is heated at 800 to 890° C. for 70 to 200 hours and then slowly cooled.

A suitable amount of the coating material is added to the granular material of the superconducting material, and the mixture is coated using a dry grinding and mixing device to produce a superconducting raw material in which the granular material of the superconducting material is covered with the coating material.

The coating material is selected from powders of suitable resins such as fluororesin, fine powders and flakes of Au, Ag, and Cu, and other suitable materials. However, select one that does not become brittle at the low temperatures at which the superconductor is used, does not react directly with the superconducting material, and does not contain water. The mixing ratio of the coating material is several percent to several tens of percent.

For superconducting materials containing Y, the melting point is 450°C.
Hereinafter, a coating material having a temperature of 300°C or less is preferably used.

Furthermore, for superconducting materials containing Bi, the melting point is 800°C.
Hereinafter, a coating material having a temperature of 400° C. or lower is preferably used.

In addition, the melting point of Au, Ag, and Cu decreases as it becomes fine powder or flake, and when it becomes on the order of 101 μm, the melting point decreases to 200 to 400 μm.
Sintering will take place at ℃. Therefore, it is used in the form of fine powder or thin slices of a thickness suitable for a predetermined melting point.

As shown in Figure 2 (a), the superconductor raw material may be one in which a large number of fine powder or flaky coating materials (B) are thermally fused to a granular material (A) of superconducting material by grinding. As shown in Figure 2 (b), a thin layer of the coating material (B) may be formed on the entire surface of the superconducting material powder (8) by thermal fusion through grinding.

The above-described grinding and mixing device will now be described in detail with reference to FIGS. 3 and 4.

A bottomed cylindrical casing (4) forming a processing chamber (3) is concentrically attached to the upper end of a vertical rotating shaft (2) attached to a base (1), and an electric motor (5a) and a variable speed Machine (5b
), etc., is interlocked with the lower end of the rotating shaft (2), and the casing (4) is driven at high speed so that the powdery raw materials inside the casing (4) are pressed against the inner circumferential surface (4a) of the casing by centrifugal force. The casing (4) is configured to rotate, and the rotational speed of the casing (4) can be adjusted so as to obtain an appropriate centrifugal force depending on the properties of the raw material.

The casing (4) is surrounded by a cover (7), a fan (12) is connected to the bottom of the casing (4), and the cover (7) is surrounded by a fan (12).
) is configured to suck outside air through an intake port (13) formed in the casing (4) and cool the casing (4) with the sucked outside air;
In addition, a conveyance channel (
1O) as a gas for transporting fine powder raw materials. In addition, the fine powder raw material is transferred from the processing chamber (3) to the cover (7).
) side, the upper center of the casing (4) is opened to form an overflow outlet (11) for the raw material.

A support (8b) having a conical portion (8c) formed at the upper center thereof is provided in the casing (4) while being fixed to the upper ends of the rotation shaft (2) and the rotation shaft (8a) of the reciprocal shaft.

A grinding piece (9a) that compresses and shears the raw material in cooperation with the inner circumferential surface (4a) of the casing, and a scraping piece (9b) that stirs, mixes and disperses the raw material are placed in an appropriate direction in the rotational direction of the casing (4). They are arranged at intervals and attached to the tip of the support (8a) and placed in the treatment chamber (3).

The grinding piece (9a) has an inclined surface formed so that the gap with the casing (4) becomes narrower in the direction of rotation of the casing (4), and the scraping piece (9b) is attached to the casing (4). ) is formed in a wedge-like or comb-like shape such that the gap between the casing (4) becomes wider in the direction of rotation of the casing (4), and its working surface gradually becomes wider.

The rotating shaft (8a) is interlocked with the drive device (5), and the grinding pieces (9a) and the scraping pieces (9b) are rotated relative to the casing (4) at a constant speed difference, thereby removing the grinding pieces (9a). The structure is such that fine pulverization by the scraper and stirring and mixing by the scraping piece (9b) are performed.

In the rotating shaft (8a), a support (8b), a grinding piece (9a)
, a passage (27) is formed through which a heating or cooling medium flows into the scraping piece (9b), and a rotary joint (2
4) connects the passageway (27) to the medium storage tank (26).

A pipe (14) is provided in the center of the cover (7) to provide a path (6) for feeding the raw material from the feeder (■9) downward toward the conical portion (8c) of the support (8b). A blower (1 unit) that supplies a suitable amount of conveying gas such as air or inert gas that is heated or cooled as necessary.
8) is connected to the path (6), and a jacket (25) is provided around the cover (7) to allow heating or cooling medium from the tank (26) to pass therethrough.

The collector (15) and the exhaust fan (16) are connected to the flow path (
10), and a rotary feeder (17) is provided at the outlet of the collector (15) to collect the fine powder raw material.

In short, the casing (4) is rotated at high speed, and the powdery raw material from the feeder (19) is delivered to the inner peripheral surface of the casing (
4a) by centrifugal force, and the raw material layer formed by the pressing is filled with crushed pieces (9
a) and the scraping piece (9b), the grinding piece (9a) finely pulverizes the raw material, and the scraping piece (9b) stirs and mixes the raw material, making it sufficiently fine and uniformly mixed. The fine powder raw material is transported by air current and collected by the collector (15).

[Another example]

Next, another embodiment will be described.

Raw materials can be appropriately selected in terms of type, mixing ratio, particle size, etc. Depending on the raw material, the calcination treatment and the secondary pulverization and mixing treatment may be performed multiple times. Further, depending on the raw materials, the calcination treatment and the secondary pulverization mixing treatment may be omitted, and the sintering treatment may be performed after the secondary pulverization mixing treatment.

The specific configuration of the dry grinding and mixing device can be changed as appropriate. For example, the rotational axis of the casing (4) may be tilted or turned sideways, or the grinding pieces (9a) and the scraping pieces (9b) may be attached to the casing (4). The shape of the grinding piece (9a) and the scraping piece (9b) may be changed by applying pressure with fluid pressure or a spring within a range that does not contact the sides, stopping the rotation of the grinding piece (9a) and the scraping piece (9b), or changing the shape of the grinding piece (9a) and the scraping piece (9b). It is possible to appropriately change the material, the number of installations, etc., or to configure the collector (15) to return and supply the fine powder to the casing (4) so as to perform batch processing.

How to set the temperature conditions in the calcination treatment and sintering treatment can be appropriately selected depending on the type of raw material.

The coating material can be appropriately selected in terms of type, melting point, and mixing ratio.

The apparatus used in the coating process can be appropriately selected from known coating apparatuses, such as a spray drying system, a fluidized drying system, a mixed granulation system, and the like.

The use of the superconductor raw material does not matter.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a flow sheet;
Figure 2<4''), (II) is a conceptual diagram of the raw material, Figure 3 is a conceptual diagram of the grinding and mixing device, and Figure 4 is the rV-mV of Figure 3.
FIG. (^)・・・Powder of superconducting material, (B)・・・
...Covering material.

Claims (1)

[Claims] 1. A superconductor raw material in which powder (A) of a superconductor material is covered with a coating material (B). 2. Powder (A) of superconducting material containing Y has a melting point of 450
A superconductor raw material covered with a coating material (B) whose temperature is below ℃. 3. Powder (A) of superconducting material containing Bi has a melting point of 80
A superconductor raw material covered with a coating material (B) at a temperature of 0°C or less.