JPH0690885B2 - PbMo Lower 6 Lower S 8 Compound Superconducting Wire Manufacturing Method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a PbMo ₆ S ₈ compound superconducting wire.

[Conventional technology]

In recent years, in the fields of nuclear fusion, high energy physics research, physical property research, and the like, there is an increasing demand for higher magnetic field of magnets, and development of superconducting magnets that generate higher magnetic fields is desired. Currently used superconducting magnet wire rods are Nb-Ti based alloys and Nb ₃ Sn based compounds and V ₃ Ga based compounds, but their critical magnetic fields are about 11T (Tesla) and about 22T at 4.2K, respectively. It is said that the maximum magnetic field obtained as a superconducting magnet is about 14T considering current capacity and efficiency. Therefore, in order to achieve a higher magnetic field, a material with a higher critical magnetic field is required.

Therefore, attention has been focused on Mo ternary chalcogenides called siebrel phase compounds. Among them, Chevrel phase lead molybdenum sulfide PbMo ₆ S ₈ (hereinafter abbreviated as PbMo ₆ S ₈ ) has a critical magnetic field of 50T or more at 4.2K. It is said that if a magnet using this compound is put into practical use, it will be possible to efficiently generate an ultrahigh magnetic field of about 20 to 30T.

Conventionally, PbMo ₆ S ₈ type compound wire has been manufactured by using PbMo ₆
A powder containing each constituent of S ₈ , for example, a mixed powder of Mo, PbS, MoS ₂ is put into a Ta or Mo tube, processed, and then heat-treated to internally generate a PbMo ₆ S ₈ compound.

However, since a compound with a good stoichiometric composition cannot be obtained by this method, the critical current density (Jc) under the magnetic field application was very low. Therefore, as shown in Japanese Patent Application No. 59-140633 (Japanese Patent Application Laid-Open No. 61-22511) as a prior example, we use a hot hydrostatic pressure device (hereinafter abbreviated as HIP device) for high temperature, Pb by processing under high pressure
We proposed a method for manufacturing Mo ₆ S ₈ compound superconducting wire. Second
The figure is a cross-sectional view of the composite before the cross-section reduction process according to the manufacturing method of the above-mentioned prior example, (4) is a mixture of Mo powder, MoS ₂ powder and Pb or PbS powder, and (2) is A Ta tube as a barrier material, and (3) a Cu tube as a stabilizing material. That is, the manufacturing method of the PbMo ₆ S ₈ based compound superconducting wire of the preceding example is
After reducing the cross section of the above composite to about 1 to 2 mm,
PbMo ₆ S _{8 with} a relatively good stoichiometric composition is obtained by heat treatment at a temperature of 0 to 1080 ° C. and a pressure of 100 Kg / cm ² or more.
A system compound is produced.

[Problems to be solved by the invention]

However, as a result of subsequent research,
Using MoS ₂ material The sulfur release initiation temperature is about 500 ℃, and the temperature at which a PbMo ₆ S ₈ compound with a good stoichiometric composition is formed is about 900〜
It was found that there is a problem that PbMo ₆ S ₈ compound with a poor stoichiometric composition is generated during the temperature rise, which is considerably lower than that of 1100 ° C, which adversely affects the properties.

The present invention has been made in order to solve such a problem, that is, PbMo ₆ S having a poor stoichiometric composition during heating.
PbMo ₆ that shows excellent electrical properties by suppressing the formation of _8- based compounds
The purpose is to obtain an S ₈ compound superconducting wire.

[Means for solving problems]

The manufacturing method of the PbMo ₆ S ₈ compound superconducting wire of the present invention is
Wood, Pb wood, and Mo whose sulfur release initiation temperature is higher than MoS ₂
The sulfide material, finally PbMo ₆ mixed material S ₈ type compound is mixed at a ratio as obtained by filling the barrier material, to obtain a complex process of reduced cross processing the complex cold , And the cross-section-reduced composite is subjected to a heat treatment process under pressure.

[Action]

In the present invention, a Mo sulfide material having a sulfur release initiation temperature higher than that of MoS ₂ is used, and the heat treatment is performed under pressure after the cross section is reduced in the cold. Therefore, a PbMo ₆ S ₈ type compound having a good stoichiometric composition is used. This prevents the formation of PbMo ₆ S ₈ type compounds with poor stoichiometric composition during the temperature rise to the temperature (900-1100 ℃) for the formation of hydrogen.

〔Example〕

 Hereinafter, the present invention will be described with reference to examples.

Example 1 FIG. 1 is a cross-sectional view of a composite body after cross-section reduction processing according to an embodiment of the present invention. (1) is a mixture, (2) is a Ta tube as a barrier material, (3) ) Is a Cu tube as a stabilizer.

That is, Mo, Pb, and Mo ₂ S ₃ powders which are the constituents of PbMo ₆ S ₈ (particle size and purity are 3 μm and 99.9%, 44 μm or less and 99.
9%, 4 μm, and 99.9%) are mixed in a molar ratio of 2: 3: 8 as evenly as possible and molded by a press to obtain a mixture (1). This mixture (1) is compounded with Ta pipe (2) which is a barrier material and Cu pipe (3) which is a stabilizing material, and the cross-section is reduced by cold drawing, and the wire is drawn to a diameter of 1.0 mm and long. A wire rod of about 30 m was obtained. The above processing showed extremely good workability without breaking.

Next, this wire is wound into a ring with a diameter of 300 mm, and both ends of this wire are sealed with Ta caps.
Put in HIP device, hydrostatic pressure of 100-2000Kg / cm ² , in this case 1
Heat treatment was performed at 900 Kg / cm ² at 800 to 1080 ° C. in this case at 1000 ° C. for 1 to 3 hours, in this case for 2 hours to obtain a PbMo ₆ S ₈ based compound superconducting wire according to an embodiment of the present invention. Inert argon gas was selected as the pressure medium. A part of the obtained wire was sampled and the critical current (Ic) characteristics under an applied magnetic field (up to 12T) were measured at liquid helium temperature (4.2K).
As a result, a very high Ic of 155A was obtained, which was about 11 times higher at 12T than the wire rod of the same structure that was heat-treated without applying conventional pressure. Also, the critical current density was improved by about 10% when compared to the HIP-treated sample under the same heat treatment condition using the MoS ₂ powder of the prior example.

FIG. 3 compares the electrical characteristics of the PbMo ₆ S ₈ type compound superconducting wire according to one embodiment of the present invention obtained as described above and the wire manufactured using the HIP device of the preceding example. It is a characteristic view which shows the electric current (Ic) change by a magnetic field (B),
(A) is a characteristic of the wire according to the embodiment of the present invention, and (B) is a characteristic of the wire according to the preceding example. According to it, the wire according to one embodiment of the present invention has a smaller Ic reduction rate on the high magnetic field side of 10 T or more as compared with the conventional HIP-treated sample using MoS ₂ powder, and the Kramer law. The critical magnetic field of the wire obtained from (Bc ₂ ^* is about 50T for the former and about 5T compared to the latter.
It is noteworthy that it turned out to be as high as 10T. In addition, this wire has a Jc ratio Jc at 10T and 12T.
(10T) / Jc (12T) is about 1.3, which is much smaller than the typical practical Nb ₃ Sn-based wire materials 2.1 to 2.4, and has a higher magnetic field (a magnetic field of 16T or more in the case of the wire material of this example). ) Showed that it had a higher Jc than the Nb ₃ Sn-based wire.

Therefore, it is considered to be effective as a winding material for an ultrahigh magnetic field magnet with a generated magnetic field of 16 T or more.

As described above, the PbMo ₆ S ₈ based superconducting wire according to the embodiment of the present invention exhibits excellent electrical characteristics because the Mo ₂ S _{3 has} a sulfur release initiation temperature of about 900 ° C and a good stoichiometric composition. PbMo ₆ S ₈
For equal Isuzu ho and a temperature of about 900 to 1100 ° C. for system compound is produced, the generation of poor PbMo ₆ S ₈ type compound having a stoichiometric composition is considered because it was prevented.

Example 2 Using the same mixture of constituents as in Example 1, a cross-section was reduced in the same manner as in Example 1 to obtain a wire drawn to a diameter of 1.2 mm. After sealing both ends of this wire with tape, it was put in nitric acid to remove the Cu tube (3) shown in FIG.

Next, this wire is wound into a ring with a diameter of 300 mm, the ends of this wire are sealed with Ta caps, and then the wire is sealed.
Placed in a HIP apparatus, hydrostatic pressure in this case 100 to 2,000 kg / cm ² is 200
At 0 Kg / cm ² , 1050 to 2200 ℃ In this case, 1100 to 1200 ℃ 1 to
In this case, heat treatment was performed for 3 hours, and for 2 hours, a PbMo ₆ S ₈ superconducting wire according to another embodiment of the present invention was obtained. Inert argon gas was selected as the pressure medium. Cu was attached to the surface of the finally obtained wire material by electric plating to obtain a stabilizing material.

Adhesion of Al in addition to Cu is also effective. A portion of the wire obtained in this way was sampled and the liquid helium temperature (4.2K)
The critical current (Ic) characteristics under an applied magnetic field (up to 12 T) were measured at. As a result, in the heat treatment temperature range of 1100 to 1200 ° C, the Ic value of the wire rod of Example 1 was higher by about 5% at 12T than that of the wire rod of Example 1.
The value of was obtained. Pressurization is 100 Kg / cm ² or more and 2000 Kg / cm
^{Although it went up to 2, the} higher the pressure is, the better the IC characteristics are obtained, and it is more effective to further increase the pressure by the pressurizing method such as diamond anvil, and the characteristics of the present invention are not impaired. In addition, when the pressure is 100 Kg / cm ² or less, the characteristics become poor.

Example 3 Composition of PbMo ₆ S ₈ type compound Pb, Mo, MoS ₂ and Mo ₂
2: (4-x): S ₃ powder (particle size is 44 μm or less, 3 μm, 2 μm and 4 μm, respectively, purity is 99.9%):
(8.3x): x is the molar ratio Mix as uniformly as possible while changing variously up to, and mold with a press to obtain a mixture (1). This mixture is subjected to cross-sectional reduction processing in the same manner as in Example 1 and drawn to a diameter of 1.0 mm to obtain a wire rod.

Next, this wire is wound into a ring with a diameter of 300 mm, the ends of this wire are sealed with Ta caps, and then the wire is sealed.
Put in a HIP apparatus, 100~2000Kg / cm ² in this case is 1800Kg / cm ²
Under hydrostatic pressure of 800 to 1080 ° C., heat treatment was performed at 950 ° C. for 1 to 3 hours in this case for 2 hours to obtain a PbMo ₆ S ₈ based compound superconducting wire according to another embodiment of the present invention. Inert argon gas was selected as the pressure medium. A part of the obtained wire was sampled and the critical current (Ic) characteristics under an applied magnetic field (up to 12T) were measured at liquid helium temperature (4.2K). As a result, HI under the same heat treatment condition using the MoS ₂ powder of the preceding example
Its critical current density is about 12T compared to the P-treated sample.
It was improved by 10%.

Pressurization was performed up to 2000 Kg / cm ² , but it goes without saying that it is effective to increase the pressure and perform the experiment.

Example 4 As a Mo sulfide material having a higher sulfur release initiation temperature than MoS ₂ which is a constituent component of the PbMo ₆ S ₈ system compound, MoS ₂ powder (particle size 2 μm
m, purity 99.9%) in a vacuum furnace at a temperature of 900 to 1000 ° C, pressure to 10 ^-3 T
Heat for 15 hours under orr to make a powder with some pre-release of sulfur. This powder is Mo, Pb powder (particle size is 3μm and 44μm under, purity is 99.9m for both
%) With a molar ratio of 8 / x: (6-8 / x): 1 respectively,
Mix uniformly while changing x variously to 1.5 <x <2, and press-mold to obtain a mixture (1).

A wire rod having a diameter of 1.0 mm is obtained from this mixture (1) in the same manner as in the manufacturing method described in Example 1.

Next, this wire is wound into a ring with a diameter of 300 mm, and both ends of this wire are sealed with Ta caps and then
Place in a HIP device, hydrostatic pressure of 100-2000 Kg / cm ² in this case 180
Heat treatment was performed at 0 Kg / cm ² at 800 to 1080 ° C. in this case at 1000 ° C. for 1 to 3 hours, in this case for 1.5 hours to obtain a PbMo ₆ S ₈ based compound superconducting wire according to another embodiment of the present invention.
Inert argon gas was selected as the pressure medium. A part of the obtained wire is sampled and the liquid helium temperature (4.2K)
The critical current (Ic) characteristics under an applied magnetic field (up to 12 T) were measured at. As a result, the critical current density at 12T was improved by about 1 to 8% as compared with the HIP-treated sample under the same heat treatment condition using the MoS ₂ powder of the prior example.

Thus, the wire according to the embodiment of the present invention gave very good results, and thus the wire according to the present invention is extremely effective as a winding material for high magnetic fields, for example.

As described above, the mixture (1) was produced from the powder as in the above embodiment, but the composition other than this powder, for example, a thin plate of Pb instead of Pb powder, may be used. Other than the above combination, any combination that produces a PbMo ₆ S ₈ based compound in the heat treatment process may be used.

As the PbMo ₆ S ₈ type compound in the present invention, for example, _{PbMo 5. 1 S 6, PbMo} 6 etc. S ₇ Mo, there are those that vary the values of S, PbMo ₆ S ₈ type collectively these It will be described as a compound. Furthermore, as M ′, for example, Ga, Bi, Ba, Sn, La, Ho, Eu, G
PbM′xMo ₆ S ₈ (x: 0.001〜 with small addition of d, Lu, Y, Nd, etc.
The 0.5) compound is also included in the PbMo ₆ S ₈ series compounds.

In addition, although the PbMo ₆ S ₈ system compound wire is a single core wire in the above-mentioned embodiment, it is possible to reduce the AC loss and stabilize the magnet by combining it with a multi-core wire and twisting. It is extremely effective and can be easily performed by the same method as the conventional Nb ₃ Sn wire.

Further, in the above embodiment, the pressurization is performed under hydrostatic pressure, but it may be performed under one pressure.

Further, in the above-mentioned embodiment, when the heat treatment temperature is 800 ° C. or higher,
The temperature is below ℃, but below 800 ℃, PbMo ₆ S ₈ type compound cannot be obtained, and the upper limit of heat treatment temperature is used as barrier material.
Mo (melting point 2617 ℃), Nb (melting point 2467 ℃), Ta (melting point 2977 ℃)
Etc.

〔The invention's effect〕

As described above, the present invention is a mixture of a Mo material, a Pb material, and a Mo sulfide material having a sulfur release initiation temperature higher than MoS ₂ in such a ratio that a PbMo ₆ S ₈ system compound is finally obtained. Stoichiometry is achieved by filling the barrier material with a barrier material to obtain a composite, cold-reducing the cross-section of the composite, and subjecting the composite with the reduced cross-section to heat treatment under pressure. PbMo ₆ S with good composition and excellent electrical characteristics
It is possible to obtain a method for manufacturing an ₈ type compound superconducting wire.

Therefore, the superconducting wire according to the present invention, conventional Nb ₃ Sn
A magnet can generate an ultra-high magnetic field of 16T or more, which could not be efficiently generated, and is useful for promoting fusion and high energy physics research, for example.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a composite body after cross-section reduction processing according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of a composite body before cross-section reduction processing according to a manufacturing method of a prior example. FIG. 3 is a characteristic diagram comparing the electrical characteristics of the PbMo ₆ S ₈ type compound superconducting wire according to the embodiment of the present invention and the prior art. In the figure, (1) is a mixture of Mo, Pb and Mo ₂ S ₃ powder, (2) is a Ta tube as a barrier material, (3) is a Cu tube as a stabilizing material, (4) is Mo, A mixture of MoS _{2 and} Pb or PbS powder, (A) is PbMo according to one embodiment of the present invention.
Properties of ₆ S ₈ compound superconducting wire, (B) is P
These are the characteristics of bMo ₆ S ₈ compound superconducting wire. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (4)

[Claims] 1. A Mo material, a Pb material, and a sulfur release initiation temperature of Mo.
The step of filling the barrier material 2 with the mixture material 1 in which the Mo sulfide material higher than S ₂ is mixed in a ratio so as to finally obtain the PbMo ₆ S ₈ type compound, and obtaining the composite body. A method for producing a PbMo ₆ S ₈ compound superconducting wire, which comprises a step of cold-working a cross-section and a step of heat-treating a composite having a reduced cross-section under pressure. 2. The PbM according to claim 1, wherein the Mo sulfide material having a sulfur release initiation temperature higher than that of MoS ₂ is Mo ₂ S ₃ material.
o ₆ S ₈ compound superconducting wire manufacturing method. 3. A sulfur free starting temperature is higher Mo sulfide material than MoS ₂ is MoS ₂ and Mo ₂ PbMo ₆ S ₈ type compound mixed material a is Claims first claim of S ₃ superconducting wire Production method. 4. The method according to claim 1, wherein the step of heat treatment under pressure is performed at a pressure of 100 kg / cm ² or more and a temperature of 800 ° C. or more.
Claim to PbMo ₆ S ₈ type compound method of manufacturing a superconducting wire according to any one of the third term.