JP2007001820A - Raw material aggregated particle powder, its producing method, superconducting wire material, its producing method, and superconducting instrument - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a raw material aggregated particle powder which is useful for producing a superconducting wire material having a high critical current; a method for producing the same; the superconducting wire material using the raw material aggregated particle powder; a method for producing the same; and a superconducting instrument including the superconducting wire material. <P>SOLUTION: The method for producing the raw material aggregated particle powder comprises: a process for arranging a raw material particle powder 1 comprising raw material particles 1a, 1b each formed from an oxide containing at least one element selected from the group consisting of Bi, Pb, Sr, Ca and Cu, or a multiple oxide in a drum 11 wherein carbon dioxide and moisture are removed; and a process for forming each raw material aggregated particle 2a by aggregating the raw material particles 1a, 1b by rotating the drum 11. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a raw material aggregated particle powder useful for producing a superconducting wire having a high critical current and a method for producing the same, and a superconducting wire produced using the raw material agglomerated particle powder, a method for producing the same, and a superconducting wire therefor Related to superconducting equipment including

  Bi-based superconducting wires containing Bi, Pb, Sr, Ca, Cu and O are typical as high-temperature oxide superconducting wires and are widely used as superconducting wires.

  Such a Bi-based superconducting wire is generally filled with a raw material particle powder stoichiometrically with respect to a chemical composition intended for Bi, Pb, Sr, Ca, Cu, and O. A metal sheath filled with powder is plastically processed to form a wire, and the wire is heat-treated. Here, the plastic working is a general term for processing in which a metal sheath filled with raw material powder is plastically deformed to form a wire rod, and includes wire drawing processing, rolling processing, press processing, and the like.

  In addition, the above raw material particle powder is mixed and mixed with oxides or carbonates containing Bi, Pb, Sr, Ca and Cu, respectively, in a stoichiometric ratio corresponding to the chemical composition of the target Bi-based superconductor. Then, the product obtained by firing is pulverized and mixed.

  The raw material particle powder thus obtained has a low bulk density and is an aggregate of tabular particles, so it has low fluidity and needs tapping when filling the metal sheath. As a result, the filling amount was uneven and the filling amount could not be increased.

  For this reason, by increasing the bulk density and fluidity of the raw material powder, uniformly filling the metal sheath with the raw material particle powder and increasing its filling amount, by increasing the cross-sectional area of the superconducting filament portion through which the superconducting current flows, In order to increase the critical current, it has been studied to produce a powder composed of raw material aggregated powder particles obtained by aggregating raw material particles.

  However, the raw material particle powder used in the production of the Bi-based superconducting wire is likely to adsorb impurities such as carbon dioxide gas and moisture, and the Bi-based superconducting wire is produced using the raw material particle powder adsorbed with the carbon dioxide gas and moisture. Even if the raw material particle powder is sintered to form a superconductor crystal, the adsorbed carbon dioxide gas and moisture are gasified, the bond between the superconductor crystals is weakened, and only a superconducting wire having a low critical current can be obtained.

As a method for producing a general raw material agglomerated particle powder, for example, an iron oxide agglomerated particle powder, various particle agglomeration methods including a dry granulation method have been proposed (for example, see Patent Document 1). The raw material particle powder used for the production of the superconducting wire has a large adsorption of carbon dioxide gas and moisture, so that no aggregation method of the raw material particle powder has been proposed so as to increase the critical current.
JP 2001-2423 A

  The present invention provides a raw material agglomerated particle powder useful for the production of a superconducting wire having a high critical current, a method for producing the same, a superconducting wire using the material agglomerated particle powder, a method for producing the same, and a superconducting device including the superconducting wire. Objective.

  In the present invention, raw material particle powder, which is an aggregate of raw material particles formed of an oxide or composite oxide containing one or more elements selected from the group consisting of Bi, Pb, Sr, Ca and Cu, is converted into carbon dioxide gas. And a raw material aggregated particle powder production method including a step of placing in a drum from which moisture has been removed and a step of aggregating the raw material particles by rotating the drum to form the raw material aggregated particles.

  In the method for producing the raw material aggregated particle powder according to the present invention, the residual carbon dioxide gas concentration in the drum can be less than 10 ppm, and the residual moisture concentration can be less than 1 ppm. Further, the internal pressure of the drum can be set to 101 kPa (1 atm) or less.

Moreover, this invention is the raw material aggregated particle powder obtained by said manufacturing method.
The present invention also includes a step of filling the raw material aggregated particle powder into a metal sheath, a step of plastically processing the metal sheath filled with the raw material aggregated particle powder to form a wire, and a step of heat-treating the wire. Is a method for manufacturing a superconducting wire.

  Moreover, this invention is a superconducting wire obtained by said manufacturing method. Furthermore, this invention is a superconducting apparatus containing said superconducting wire.

  According to the present invention, a raw material aggregated particle powder useful for the production of a superconducting wire having a high critical current and a method for producing the same, a superconducting wire using the raw material agglomerated particle powder, a method for producing the same, and a superconducting device including the superconducting wire are provided. be able to.

  The raw material aggregated particle powder manufacturing method according to the present invention is described with reference to FIG. 1 and FIG. 2. An oxide or composite oxidation containing one or more elements selected from the group consisting of Bi, Pb, Sr, Ca and Cu A raw material particle powder 1, which is a mixture of raw material particles formed in a product, is disposed in a drum 11 from which carbon dioxide gas and moisture have been removed, and the raw material particles 1 a and 1 b are agglomerated by rotating the drum. Forming the agglomerated particles 2a.

Here, the raw material particle powder refers to an aggregate of raw material particles formed of an oxide or composite oxide containing one or more elements selected from the group consisting of Bi, Pb, Sr, Ca and Cu. The raw material particle powder may contain two or more kinds of raw material particles having different chemical compositions. Specifically, the raw material particle powder includes Bi2212 (Bi ₂ Sr ₂ CaCu ₂ O _{8 + δ} , hereinafter the same) particles, (Bi, Pb) 2212 ((Bi, Pb) ₂ Sr ₂ CaCu ₂ O. _{8 + δ} , hereinafter the same) particle, Bi2223 (Bi ₂ Sr ₂ Ca ₂ Cu ₃ O _{10 + δ} , hereinafter the same) particle, (Bi, Pb) 2223 ((Bi, Pb) ₂ Sr ₂ Ca ₂ Cu ₃ O _{10 + δ} , hereinafter the same) particles, alkaline earth oxide particles, alkaline earth copper oxide particles, copper oxide particles, Ca ₂ PbO ₄ particles, (Bi, Pb) 3221 ((Bi, Pb) ₃ Sr ₂ Ca ₂ CuO _{10 + δ} , hereinafter the same) particles, or particles containing two or more different oxides or composite oxides in the above chemical composition.

  This raw material particle powder is prepared by mixing and mixing oxides or carbonates containing Bi, Pb, Sr, Ca and Cu at a stoichiometric ratio corresponding to the chemical composition of the target Bi-based superconductor. It is manufactured by pulverizing and mixing the product obtained by firing.

Such raw material particle powder is composed of flat raw material particles having a diameter of about 1 μm to 4 μm and a thickness of about 0.1 μm to 5 μm, and the bulk density of the powder is 0.5 g / cm ^{3 to} 0.7 g / cm ^3. The degree becomes low.

  For the production of the raw material aggregated particle powder according to the present invention, for example, a rotary granulator 10 is used with reference to FIG. This rotary granulator 10 has one drum 11 mounted on two rollers 12, and the drum 11 is rotated by rotating the roller 12, and the raw material particle powder disposed in the drum 11. The raw material agglomerated particles 2a can be agglomerated by bringing the raw material particles 1a and 1b constituting 1 into agglomeration by bringing them into contact with each other.

  The raw material aggregated particle powder manufacturing method according to the present invention includes a step of placing the raw material particle powder 1 in a drum 11 from which carbon dioxide gas and moisture have been removed, with reference to FIG. By aggregating the raw material particles 1a and 1b in the drum 11 from which carbon dioxide gas and moisture have been removed, the raw material particles can be aggregated without adsorbing the carbon dioxide gas and moisture on the particle surface. In this way, since the raw material aggregated particle powder without adsorption of carbon dioxide gas and moisture is obtained on the particle surface, there is no risk of lowering the bonding force between the superconductor crystals due to carbon dioxide gas and moisture in the subsequent production process of the superconducting wire. Thus, it becomes possible to produce a superconducting wire having a high critical current.

  Here, the concentration of carbon dioxide gas and moisture remaining in the drum 11 is preferably as low as possible for the purpose of the invention. The residual carbon dioxide gas concentration in the drum 11 is preferably less than 10 ppm, and more preferably 1 ppm or less. The residual moisture concentration in the drum 11 is preferably less than 1 ppm (dew point temperature less than −80 ° C.), more preferably 0.1 ppm or less (dew point temperature −90 ° C. or less).

  Moreover, the manufacturing method of the raw material aggregated particle powder concerning this invention includes the process of aggregating the raw material particle powder 1a, 1b by rotating the drum 1, and forming the raw material aggregated particle 2a with reference to FIG. Here, the raw material aggregated particle powder 2 refers to an aggregate of the raw material aggregated particles 2a and 2b formed by aggregating the raw material particles constituting the raw material particle powder.

  The mechanism by which the raw material particles aggregate to form the raw material aggregated particles is considered as follows. Referring to FIG. 2, by rotating drum 11, any raw material particle 1 a located near the surface of raw material particle powder 1 makes contact with other raw material particles 1 b while rolling near the surface of raw material particle powder 1. Repeatedly, the raw material particles 1a and 1b are agglomerated by the self-aggregating force that works to minimize the surface energy to form the raw material agglomerated particles 2a. When the drum 11 further rotates, the raw material aggregated particles 2a become larger while repeating the above process. In this way, the raw material aggregated particle powder 2 which is a mixture of the raw material aggregated particles 2a and 2b is obtained.

Here, the raw material agglomerated particles 2, the particle size is composed of granular material aggregated particles 2a, 2b of about 10Myuemu～5mm, the bulk density of the powder is 0.8g / cm ³ ~1.4g / cm ³ degree Larger and more fluid. For this reason, the raw material aggregated particle powder 2 can be uniformly filled in the metal sheath without tapping, and the filling amount can be increased. By uniformly filling the metal sheath with the raw material aggregated particle powder and increasing the filling amount, the thickness of the superconducting filament through which the superconducting current flows is made uniform and the cross-sectional area of the superconducting filament is increased. Manufacture is possible.

  In the method for producing the raw material aggregated particle powder according to the present invention, referring to FIG. 2, the internal pressure of the drum 11 is not particularly limited, but is preferably 101 kPa or less. The raw material agglomerated particles 2a are agglomerated by the self-aggregating force of the raw material particles 1a and 1b. Since the aggregating force is small, there is a high possibility that the agglomerated particles are separated again when the drum internal pressure is high. From this viewpoint, the internal pressure of the drum 11 is more preferably 1 kPa or less, and further preferably 1 Pa or less.

  As described above, the production of the raw material agglomerated particle powder according to the present invention is performed by a simple operation of simply rotating the drum, so that the production cost can be reduced. Further, since a simple device with a drum withstand pressure of 101 kPa or less is sufficient, the equipment cost can be reduced.

  Moreover, since the raw material aggregated particle powder according to the present invention can be produced in a room temperature atmosphere of about 10 ° C. to 30 ° C., the raw material aggregated particles can be formed without changing the physical properties of the raw material particles. Therefore, it is easy to manufacture a superconducting wire having the desired characteristics.

  Moreover, since the raw material aggregated particle powder according to the present invention is obtained by the above production method, it is possible to fill the metal sheath uniformly and at a high density, and to form a superconducting wire having a high critical current. It becomes a suitable raw material.

  The superconducting wire manufacturing method according to the present invention includes a step of filling the raw material aggregated particle powder in a metal sheath, a step of plastically processing the metal sheath filled with the raw material aggregated particle powder, and forming a wire, Heat-treating the wire. By filling the raw material aggregated particle powder into the metal sheath, it is possible to uniformly fill the metal sheath and increase the filling amount, thereby producing a superconducting wire having a high critical current.

  In addition, since the superconducting device according to the present invention includes the superconducting wire having a high critical current, the superconducting device has excellent superconducting characteristics. Here, the superconducting device is not particularly limited as long as it includes the superconducting wire, and examples thereof include a superconducting cable, a superconducting coil, a superconducting transformer, a superconducting current limiter, and a superconducting power storage device.

Example 1
Bi ₂ O ₃ , PbO, SrCO ₃ , CaCO ₃ and CuO powders as raw materials are blended in a stoichiometric ratio so as to have a standard composition of Bi _1.8 Pb _0.3 Sr _1.9 Ca _2.0 Cu _3.0 O _{10 + δ} . After mixing, the polycrystal obtained by firing at 780 ° C. for 8 hours in an atmosphere of 101 kPa oxygen and nitrogen mixed gas (oxygen concentration 8% by volume) was pulverized to prepare raw material particle powder. The raw material particle powder was a mixture of flat raw material particles having a bulk density of 0.7 g / cm ³ , a diameter of 1 μm to 4 μm, and a thickness of 0.1 μm to 5 μm. Here, the bulk density (ρ) is measured by adding a certain volume V (unit cm ³ ) of raw material particle powder or raw material aggregated particle powder to a measuring cup, and measuring the mass M (unit g) of the particle powder. Calculated from / V. The particle size was measured by SEM (scanning electron microscope).

  Next, referring to FIG. 2, 2000 g of raw material particle powder 1 was placed in a drum 11 having an inner diameter (D) of 15 cm × an inner length (L) of 34 cm. Next, the air in the drum 11 is purged for 1 hour using dry air having a carbon dioxide gas concentration of 1 ppm or less and a moisture concentration of 0.1 ppm or less, and then the dry air in the drum 11 is removed by a vacuum pump to reduce the drum internal pressure. The residual carbon dioxide gas concentration in the drum was 0.1 ppm or less, and the residual moisture concentration in the drum was 0.1 ppm or less (dew point temperature −90 ° C. or less).

Next, by rotating the drum 11 at 57 rpm for 4 hours at an atmospheric temperature of 30 ° C., the raw material aggregated particle powder 2 which is a mixture of the raw material aggregated particles 2a and 2b obtained by aggregating the raw material particles 1a and 1b is formed. It was. The obtained raw material aggregated particle powder was a mixture of raw material aggregated particles having a bulk density of 0.95 g / cm ³ and a particle size of 10 μm or more.

  Next, the raw material aggregated particle powder was filled in a silver tube having a diameter of 46 mm and then drawn to obtain a clad wire having a diameter of 10 mm. The 55 clad wires were bundled and inserted again into a silver tube having a diameter of 46 mm, followed by wire drawing to obtain a multicore wire in which the raw material powder was in the form of a filament.

  Next, the multi-core wire was subjected to primary rolling to obtain a tape-like silver-coated wire having a silver ratio of 1.5 and a width of 4.2 mm and a thickness of 0.24 mm made of 55-core filaments.

  Next, the tape-shaped silver-coated wire is subjected to a first heat treatment in an atmosphere of 101 kPa oxygen and nitrogen mixed gas (oxygen concentration: 8% by volume) at 825 ° C. for 30 hours to produce a primary superconducting wire. (Primary wire) was obtained. In addition, silver ratio means ratio of the area of the silver part with respect to the area of the filament part in the cross section (width x thickness cross section) of a wire.

Next, the primary wire was subjected to secondary rolling at a rolling reduction of 8%. The rolling reduction is the following formula (1)
Reduction ratio (%) = {1- (Thickness of wire after rolling) / (Thickness of wire before rolling)} × 100 (1)
Is defined by

  Next, the second heat treatment was performed on the wire after the second rolling in an atmosphere of 101 kPa oxygen and nitrogen mixed gas (oxygen concentration 8% by volume) at 822 ° C. for 50 hours to obtain a superconducting wire (secondary wire). Got.

When the critical current of the obtained superconducting wire was measured under the conditions of 77K and 0T by the four probe method, a large value of 130A was obtained. Here, the critical current was defined as a current when a voltage of 1 μV per 1 cm of superconducting wire was generated. The results are summarized in Table 1. Here, in Table 1, the sectional area occupation ratio (%) of the powder refers to the sectional area occupied by the raw material powder (S ₀ + S ₁ ) with respect to the sectional area (S ₀ + S ₁ ) in the vertical direction of the drum 11 with reference to FIG. ₁ ) percentage (100 × S ₁ / (S ₀ + S ₁ )). Further, the peripheral speed v (m / s) refers to the rotational speed on the inner periphery of the drum 11 with reference to FIG.

(Examples 2 to 7)
Using the raw material particle powder produced in the same manner as in Example 1, raw material aggregated particle powder was produced under the conditions shown in Table 1. Table 1 shows the bulk density of the obtained raw material aggregated particle powder. As is apparent from Table 1, a powder having an appropriate bulk density can be easily obtained by the method for producing the raw material aggregated particle powder according to the present invention.

(Comparative Example 1)
A superconducting wire was produced in the same manner as in Example 1 except that the raw material particle powder itself was filled in the silver tube without producing the raw material aggregated powder from the raw material particle powder. The critical current of the obtained superconducting wire was 100A. The results are summarized in Table 1.

(Comparative Example 2)
A superconducting wire was produced in the same manner as in Example 1 except that the raw material particles constituting the raw material particle powder were aggregated by a wet spray (spray drying) method to form the raw material aggregated particles. The critical current of the obtained superconducting wire was 90A. The results are summarized in Table 1.

  Here, the wet spray method refers to droplets generated by spraying a slurry in which raw material particle powder is dispersed in a volatile solvent such as alcohol into a furnace in a high temperature (for example, 120 ° C. to 240 ° C.) airflow. This means that raw material aggregated particles obtained by instantaneously vaporizing and aggregating the raw material particles are collected to produce a raw material aggregated particle powder. In Comparative Example 2, the raw material aggregated particles are obtained by spraying a slurry in which raw material particles are dispersed in ethanol as an alcohol into a cylindrical indirect heating furnace in a nitrogen gas stream at 140 ° C. and collecting the slurry by a bag filter recovery method. A powder was prepared.

In Example 1 of Table 1, the raw material particles constituting the raw material particle powder are arranged in a drum from which carbon dioxide gas and moisture have been removed, and the drum is rotated so that the raw material particles are aggregated to form a granular raw material aggregate. Particles were formed. The raw material agglomerated powder composed of the raw material agglomerated particles has a higher bulk density than the raw material particle powder (the bulk density of the raw material particle powder in Comparative Example 1 is 0.7 g / cm ³ , and the raw material agglomerated particle powder in Example 1 Since the bulk density is 0.95 g / cm ³ ) and the fluidity is high, the metal sheath can be filled uniformly and densely without tapping, and the superconducting wire having a high critical current (superconductivity in Comparative Example 1) The critical current of the wire was 100 A, and the critical current of the supercritical current in Example 1 was 130 A).

On the other hand, according to Comparative Example 2 in Table 1, the raw material aggregated powder composed of the raw material aggregated powder obtained by aggregating the raw material particles by the wet spray method also has a higher bulk density than the raw material particle powder (in Comparative Example 1). The bulk density of the raw material particle powder is 0.7 g / cm ³ , the bulk density of the raw material aggregated particle powder in Example 1 is 1.2 g / cm ³ ), and the fluidity is high. Although the superconducting wire obtained could be filled with high density, the critical current of the obtained superconducting wire was low (the critical current of the superconducting wire in Comparative Example 1 was 100 A, and the critical current of the supercritical current in Comparative Example 2 was 90 A).

  This is because in the particle agglomeration method by the wet spray method, carbon dioxide gas generated by decomposition or oxidation of alcohol due to heat generated when vaporizing the alcohol as a solvent is adsorbed and remains on the material agglomerated particles. When a superconducting wire is manufactured by plastically deforming a metal sheath filled with the raw material aggregated particle powder and sintering it by heat treatment, the residual carbon dioxide gas weakens the bond between the superconductor crystals and lowers the critical current. It is thought that.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a schematic diagram which shows an example of the apparatus used in the manufacturing method of the raw material aggregated particle powder concerning this invention. It is a schematic diagram which shows the cross section of the II direction of FIG.

Explanation of symbols

  1 Raw material particle powder, 1a, 1b Raw material particle, 2 Raw material agglomerated particle powder, 2a, 2b Raw material agglomerated particle, 10 rotary granulator, 11 drum, 12 roller.

Claims (7)

  Carbon dioxide gas and moisture remove raw material particle powder, which is an aggregate of raw material particles formed of an oxide or composite oxide containing one or more elements selected from the group consisting of Bi, Pb, Sr, Ca and Cu A method for producing agglomerated raw material powder comprising a step of arranging in a drum and a step of aggregating the raw material particles to form raw material agglomerated particles by rotating the drum.   The method for producing a raw material aggregated particle powder according to claim 1, wherein the carbon dioxide gas residual concentration in the drum is less than 10 ppm and the moisture residual concentration is less than 1 ppm.   The method for producing a raw material aggregated particle powder according to claim 1 or 2, wherein an internal pressure of the drum is 101 kPa or less.   Raw material aggregated particle powder obtained by the production method according to any one of claims 1 to 3.   Filling a metal sheath with the raw material aggregated particle powder according to claim 4, forming a wire by plastic working the metal sheath filled with the raw material aggregated particle powder, and heat-treating the wire A method of manufacturing a superconducting wire including   A superconducting wire obtained by the production method according to claim 5.   A superconducting device comprising the superconducting wire according to claim 6.

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