JPH0453051B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a compound superconductor, for example, a long A
The present invention relates to a method for stably and efficiently manufacturing a -15 type compound superconductor or a long Siebrel type compound superconductor. (Prior art) As is well known, the compound superconductors currently in practical use include Nb ₃ Sn and V ₃ Ga, both of which are produced by diffusion reactions between metal elements, such as surface diffusion methods and composite processing methods. It is manufactured using a method using
However, magnets made using Nb ₃ Sn or V ₃ Ga have an upper critical magnetic field of about 20 Tesla, so the generation of a magnetic field up to 20 Tesla is said to be the limit. On the other hand, as an A-15 type compound superconductor with superconducting properties superior to the above-mentioned Nb ₃ Sn and V ₃ Ga,
Nb ₃ Al, Nb ₃ Ga, Nb ₃ Ge, and Nb ₃ (Al・Ge) are known, and are also known as Hsiebrel-type compound superconductors.
PbMo ₆ S ₈ etc. are known, and these are all
It has an upper critical magnetic field of 30 Tesla or more. However, when these A-15 type compound superconductors and Siebrel type compound superconductors are produced by the above-mentioned diffusion method, the crystal grains become coarse because the production temperature is extremely high. As a result, the critical current density, which is an important factor when applied to superconducting magnets, is significantly reduced. Other fabrication methods include sputtering, CVD, and other vapor-phase deposition methods, but both are laboratory-scale and have limitations in production speed. For this reason, these methods currently have a width of 1 cm, a length of several cm, and a thickness of 2 to 3 μm.
The limit was to obtain a superconductor of about 100%. As described above, conventional methods have the problem that it is difficult to make the superconductor long, and good superconducting properties can only be obtained with a film thickness of 2 to 3 μm, so the critical current is only a few hundred mA at most. It is a small thing. As mentioned above, the A-15 type compound superconductor and Siebrel type compound superconductor described above are made of Nb ₃ Sn,
Although it is known to have a higher critical temperature and higher upper critical magnetic field than V ₃ Ga, a method for fabricating it so that it has a high critical current and critical current density and can be made long has not been solved. (Problems to be Solved by the Invention) The present invention has been made in view of the above circumstances, and its purpose is to use a long material having a high critical current, such as an A-15 type compound superconductor or a Siebrel superconductor. The object of the present invention is to provide a method for easily and stably manufacturing a type compound superconductor. (Means for Solving the Problems) In order to achieve the above object, in the production method of the present invention, a porous molded body or a sintered body containing at least one element out of a plurality of elements constituting a compound superconductor is manufactured. A first composite body consisting of a solid body is manufactured, and this first composite body is immersed in a melt having the remaining constituent elements so that the melt penetrates therebetween, and is then solidified to form a second composite body. The first step is to obtain a composite, and after the second composite obtained in the first step is lengthened, the surface of the second composite is defined along the longitudinal direction. A compound superconducting layer is generated in the melted and solidified portion by irradiating the laser beam at a relative speed, and by this irradiation, the surface portion of the second composite is rapidly melted, and then rapidly cooled and solidified. and a second step of causing. Further, this invention will be described in detail. First step A-When manufacturing a 15-type compound superconductor A sintered body of a predetermined shape or a molded body obtained by pressure-molding the powder using a powder mainly composed of niobium or a plurality of wires mainly composed of niobium A porous first composite body made of the following materials is manufactured. Here, the term niobium as the main component means that it includes not only niobium alone but also a mixture of niobium and one or two of aluminum, germanium, and gallium. However, in this case, the melting point of the first composite needs to be higher than the melting point of the melt. Next, this first composite is mixed with one or two selected from aluminum, germanium, and gallium.
A second composite is created by immersing the seed or more in the melt. In this case, the proportion of the melt in the second composite is preferably 5 to 50% by volume. If the melt is too small, even if laser irradiation is performed in the second step, the A-15 type compound will not be generated sufficiently, and if it is too large, compounds other than the A-15 type compound will be generated, and in either case, the superconducting properties will be significantly reduced. This is because it deteriorates. The proportion of the molten material in the second composite can be adjusted by changing the sintering conditions, pressurizing conditions, etc. of the first composite to adjust the porosity. Note that the first composite is preferably inserted into the niobium tube before or after being immersed in the melt, so that it can be easily lengthened in the subsequent process. When manufacturing a Siebrel-type compound superconductor, first, M (M is one metal element selected from lead, tin, copper, and silver), a sulfide of M, sulfur, molybdenum, and a sulfide of molybdenum are selected from the group. A porous first composite body is made from one or more types of powder, such as a sintered body or a molded body obtained by compacting the powders. Next, one or two selected from the above group.
The first composite is immersed in a melt of at least one component having a melting point lower than that of the first composite, and then solidified to form a second composite. Specifically, M powder, M sulfide powder, or a mixture thereof is mixed with Mo powder, Mo sulfide powder, or a mixture thereof to form a first composite, and this is mixed with sulfur. A second composite is created by dipping into the melt. Alternatively, a first composite of molybdenum sulfide powder is immersed in a melt of metal M and then solidified to form a second composite. Alternatively, one powder selected from metal M sulfide powder, molybdenum powder, and a mixture thereof was added to molybdenum sulfide powder to form a first composite, and this was immersed in the metal M melt. Post solidification creates a second composite. The first composite is preferably inserted into the molybdenum tube before or after being immersed in the melt to facilitate lengthening in the subsequent process. Second Step After the second composite obtained in the first step is lengthened, it is irradiated with a laser beam in the above relationship. Laser beam irradiation is performed in vacuum or Ar gas. The power density of the laser beam is set to 10 ⁴ W/cm ² or more at the irradiation location. If it is less than 10 ⁴ W/cm ² , the sample will not be heated sufficiently and the constituent elements will not react with each other. Therefore, a compound superconductor cannot be formed. Moreover, preferable results can be obtained if the second step includes a step of performing heat treatment before and after laser beam irradiation. These heat treatment steps contribute to improving superconducting properties. In particular, the heat treatment before laser beam irradiation serves to cause the constituent elements to react with each other in advance and to assist in the formation of a superconductor by subsequent laser beam irradiation. However, it is necessary to limit the heat treatment temperature at this time to 400 to 2000°C, preferably 800 to 1500°C. If the heat treatment temperature is less than 400℃, the reaction between the constituent elements will hardly proceed;
If it exceeds this amount, compounds other than superconductors will be formed and favorable results will not be obtained. On the other hand, heat treatment after laser beam irradiation increases the regularity of the crystals of the compound formed by laser beam irradiation and contributes to improving superconducting properties. In this case as well, the heat treatment temperature was set to 300
It is necessary to limit the temperature to ~1500°C, preferably 500~1000°C. When the heat treatment temperature is less than 300°C, almost no movement of elements occurs, so it hardly contributes to improving crystal regularity. If the heat treatment temperature exceeds 1500°C, the crystal grains will become coarser and the superconducting properties will deteriorate. (Effects of the Invention) According to the manufacturing method of the present invention, after the second composite obtained in the first step is lengthened, the surface of the second composite is lengthened along the longitudinal direction. The laser beam is irradiated at a predetermined relative speed, and the surface of the second composite is sequentially rapidly melted by this irradiation, and then rapidly cooled and solidified, so that the mixing of the reaction materials is achieved by rapid melting. It is possible to accelerate the reaction and to make the reaction uniform, and it is also possible to make the reaction crystal finer by rapid cooling and solidification. Compound superconductors can be easily produced. In particular, in the manufacturing method of the present invention, in the first step, the porous first composite is immersed in the melt to allow the melt to penetrate between the first composites, and then solidified. Since the second composite is obtained, the adhesion of each component constituting the second composite is improved, and the reactivity is improved.
The performance of the resulting compound superconductor can be improved. In addition, in the second step, the surface of the second composite obtained in the first step is simply irradiated with a laser beam, so either the laser beam is fixed and the molded object is moved at high speed, or A long superconductor can be easily produced by, for example, sweeping the laser beam at high speed while fixing the second composite body. Furthermore, since it is possible to form a superconductor layer several 100 μm thick by laser beam irradiation, a superconductor with a sufficiently high critical current I _c can be produced. As described above, according to the manufacturing method of the present invention, the critical temperature is lower than that of Nb ₃ Sn and V ₃ Ga, which are currently in practical use.
A long compound superconductor with much higher T _c , critical magnetic field B _c2 , and critical current density J _c can be easily manufactured. Therefore, it can contribute to the realization of a superconducting magnet that generates a stronger magnetic field. In addition, conventional Nb ₃ Sn, V ₃ Ga superconductors are
Because it is manufactured using a composite processing method, it requires many steps such as wire drawing, extrusion, and intermediate annealing, and the final step, diffusion heat treatment, requires several dozen to several steps.
It requires 100 hours. However, according to the manufacturing method of the present invention, a superconductor can be manufactured by laser beam irradiation in an extremely short period of time, so manufacturing costs can be significantly reduced. (Embodiments of the invention) Examples of the invention will be described below. Example 1 Production of A-15 type compound superconductor 200 g of Nb powder with a purity of 99% and a particle size of 100 μm was pressurized.
It was molded and sintered by heating at 2200°C for 1 hour. This sintered body (first composite body) was immersed in an Al bath at about 800° C., and Al penetrated into the gaps of the sintered body and solidified to obtain a second composite body. In this case, the proportion of Al in the second composite was 20% by volume. Then this
It was inserted into a Nb tube, then drawn and rolled to obtain a tape-shaped composite (sample number 1) with a width of 4 mm and a thickness of 200 μm. Composites (sample numbers 2 to 5) were obtained under the same manufacturing conditions except that the material of the melt was changed (see column 1A of Table 1 below). A compound superconducting layer was formed on the surface of the sample thus prepared by irradiating it with a laser beam. The laser irradiation device 1 used here is the
This is the structure shown in the figure. That is, 2 in the figure is a CO ₂ laser oscillator (maximum output 10kW). A laser beam 3 sent out from this CO ₂ laser oscillator 2 passes through a Cu reflector 4 and a ZnSe lens 5 to a vacuum vessel 6.
I am beginning to be guided within. A feed drum 8 for sending out the sample 7 and a winding drum 9 for winding up the sample 7 are provided in the vacuum container 6. After the sample 7 sent out from the feed drum 8 is irradiated with the laser beam 3, It is adapted to be wound up on a winding drum 9. Further, the vacuum container 6 is selectively connected to an exhaust pump 10 and an Ar gas cylinder 11. Then, each sample was irradiated with a laser beam in the following manner. That is, first, sample 7
After setting the feed drum 8 and take-up drum 9, the pressure inside the vacuum container 6 is reduced to 10 ^-5 torr, and then
Ar gas was introduced to create a pressure of 1 atmosphere. Next, sample 7
While unwinding from the winding drum 8 at a speed of 10 m/min, the laser beam 3 with the power density shown in Table 1 is applied.
(laser beam diameter: 1 mm) was irradiated onto the surface of sample 7. When we observed the samples that had been irradiated in this way, for example, the samples that had been irradiated with a laser beam with a power density of 3.1×10 ⁵ W/cm ² (power 2.5 kW, beam diameter 1 mm), as shown in Figure 2, A compound superconductor 12 having a width of about 0.5 mm and a depth of about 0.1 mm was formed on the surface side of the sample 7. And the surface is
It looked like welding marks. For each sample in which a compound superconducting layer was formed in this way, the critical temperature T _c and critical current I _c at 17 Tesla were measured, and the results shown in column b of Table 1 were obtained. As can be seen from these results, each sample
T _c is sufficiently high, and I _c also has a value of 10A or more. This is 4× when converted to critical current density J _c
This is a large value of 10 ⁴ A/cm ² or more. The I _c of compound superconductors obtained by conventional vapor phase deposition is several hundred at most.
Considering that it is mA, the adoption of this manufacturing method results in an improvement of about two orders of magnitude or more. Further, when the characteristics in the longitudinal direction of each sample were examined, it was confirmed that the characteristics were the same as those in column b of Table 1 for a length of 30 cm. That is, by employing this manufacturing method, a long compound superconductor having sufficiently high T _c and I _c can be easily manufactured. Therefore, by using the compound superconductor produced by this production method, it is possible to produce a superconducting magnet that generates a strong magnetic field of 20 Tesla or more, which was previously considered impossible. On the other hand, after laser beam irradiation, a portion of each sample was heat-treated at 700°C for 100 hours. As a result, as shown in column c of Table 1, each sample was 1K
In addition to the above increase in T _c , an increase in I _c at 17 Tesla was also observed. In addition, a portion of each sample was heat-treated at 1000°C for 30 minutes before laser beam irradiation. Regarding the above part of each sample after laser beam irradiation
When T _c and I _c were measured, it was confirmed that each was improved as shown in column d of Table 1. Furthermore, a portion of each sample that obtained the results in column d of Table 1 was subjected to heat treatment at 700° C. for 100 hours after laser beam irradiation. For these parts, T _c
When T c and I _c were measured, as shown in column e of Table 1, an increase in T _c and I _c was observed in each sample. Therefore, it has been found that it is effective to perform heat treatment before and after laser beam irradiation.

[Table] Example 2 Approximately 800 fine Nb wires with a purity of 99% and a diameter of 300 μm were bundled and inserted into a Nb tube, and heated at 2200° C. for 1 hour to sinter the Nb wires together. This is Al-10 atomic% at about 800℃.
The sintered body (first composite body) was immersed in a Ge bath to infiltrate the Al-Ge alloy into the gaps of the sintered body (first composite body) and solidified to obtain a second composite body. In this case, Al−Ge in the second complex
The proportion of alloy was 20% by volume. This was then drawn and rolled into a tape having a width of 7 mm and a thickness of 0.2 mm. After that, the tape-shaped composite was treated as in Example 1.
A laser beam with a power density of 3.1×10 ⁵ W/cm ² (power 2.5 kW, beam diameter 1 mm) was irradiated. Regarding the sample obtained in this way, the T _c and I _c at 17 Tesla were measured, respectively.
Values of 17.0K and 22A were obtained. Add this sample to
When heat treated at 700℃ for 100 hours, T _c and I _c of 17 Tesla
rose to 19.2K and 25A, respectively. From the above results, it can be seen that even if Nb wire is used in place of the Nb powder used in Example 1, high superconducting properties can be obtained by laser beam irradiation. Example 3 In the process of manufacturing the sintered body of Example 2, samples were prepared in which the number of Nb wires used was varied and the proportion of the Al10 atomic%Ge alloy in the second composite was 2 to 65% by volume. was created. The volume fraction % was calculated by observing the cross section of the sample with an optical microscope. Each sample has a power density of 3.1×10 ⁵ W/cm ² (power
I _c was measured at 17 tesla by irradiating with a laser beam of 2.5 kW, beam diameter 1 mm), and the influence of the ratio of Nb and Al-Ge alloy on I _c at 17 tesla was investigated. As a result, as shown in Figure 3, Al-
It can be seen that _Ic is particularly high when the volume fraction of the Ge alloy is 5 to 50%, and that an A-15 type superconductor having good superconducting properties can be obtained in this range. Example 4 Production of Siebrel type compound superconductor 40g of Pb powder with purity of 99% and particle size of 100μm and purity
After mixing with 160 g of 99.9% Mo powder having a particle size of 10 μm, the mixture was press-molded and then heated at 300° C. for 5 hours to sinter. This sintered body (first composite body) is immersed in a sulfur bath at 300°C to allow sulfur to penetrate into the gaps between the sintered bodies and solidify.Then, the sintered body is inserted into a Mo tube, drawn, and rolled to a width of 4 mm. A tape-shaped composite (sample number 6) with a thickness of 200 μm was obtained. A composite (sample number 7) was prepared in the same manner as sample 6 except that the materials of the sintered body and molten body were changed.
~10) were prepared (see column 2a in Table 2). The surface of the sample thus prepared was irradiated with a laser beam in the same manner as in Example 1 to form a compound superconducting layer, and the T _c of this layer and I _c of 17 Tesla were
was measured. As shown in column b of Table 2,
Sufficiently high T _c and I _c were obtained for all samples.
The laser irradiation reaction area in the sample has a width of 0.5 mm and a depth of 0.1 mm, as in Example 1.
J _c becomes 4×10 ⁴ A/cm ² or more. Next, as in Example 1, the influence of heat treatment before and after laser irradiation was investigated. Column c in Table 2 shows the value when heat treated at 500℃ for 100 hours after laser irradiation.
Column d in Table 2 is the value when the sample was heat treated at 1000°C for 30 minutes before laser beam irradiation, and column e in Table 2 is the value when the sample in column d was heat treated at 500°C for 100 hours after laser beam irradiation. From these results, in both cases, heat treatment
An increase in T _c and I _c was observed, indicating that heat treatment before and after laser beam irradiation is effective.

[Table] Example 5 Sample number 2 (Nb-
Eight samples each having the same composition as the sample number 6 (Pb-Mo-S) shown in column 2a of Table 2 of Example 4 were prepared. 1.0×10 ³ to 1.2× for each sample
Laser beams with different power densities within the range of 10 ⁶ W/cm ² were applied. The beam diameter at this time was 1 mm in each case. For each sample, at 17 Tesla
I _c was measured and the dependence of I _c on laser power density was investigated. As a result, as shown in FIG. 4, it is found that a laser power density of 10 ⁴ W/cm ² or more is required to obtain a high critical current I _c . However, in FIG. 4, A is niobium-gallium and B is Pb-Mo-S. In this example, CO ₂ with a maximum output of 10 kW
1.2×10 ⁶ W/cm ² due to the use of a laser oscillator
Although it was not possible to irradiate a laser beam with a power density exceeding 1.2×10 ^{6 W/cm 2 (power 10 kW, beam diameter 1 mm), the results shown in Figure 4 show that sufficiently high characteristics can be obtained even with a power density exceeding 1.2 × 10 6} W/cm ² . It can be determined that Example 6 Sample number 5 shown in column a of Table 1 of Example 1
Prepare 15 samples similar to (Nb-Al-Ge alloy), heat treat each sample at different temperatures within the range of 100 to 2500℃ for 30 minutes, and then irradiate the power density of 3.1 x 10 ⁵ W. /cm ² (power 2.5kW, beam diameter /
A compound superconductor was obtained by irradiation with a laser beam of mm). For these superconductors, at 17 Tesla
I _c was measured and the dependence of I _c on heat treatment temperature was investigated. The results are shown in FIG. Note that the values of a superconductor of the same composition without heat treatment are shown in FIG. From the figure, it can be seen that a heat treatment temperature of 400 to 2000°C, particularly 800 to 1500°C, before laser beam irradiation is effective. Example 7 Twelve samples similar to those used in Example 6 were prepared, and ^each sample was heat-treated at 1000°C ^for 30 minutes. , a laser beam with a beam diameter of 1 mm) was irradiated. After irradiation, each sample was heat treated at different temperatures within the range of 100-1800°C for 100 hours. The I _c of the 12 superconductors thus obtained was measured under the condition of 17 Tesla. The results are shown in FIG. Note that D in the figure is the value of a superconductor of the same composition that was not heat-treated after laser beam irradiation. From the figure, it can be seen that a heat treatment temperature of 300 to 1500°C, particularly 500 to 1000°C, after laser beam irradiation is effective. Example 8 Sample number 1 shown in column a of Table 1 of Example 1
We prepared 11 samples similar to (Nb-Al alloy),
These samples have a power density of 3.1×10 ⁵ W/cm ² (power
After irradiation with a laser beam of 2.5 kW (beam diameter 1 mm), heat treatment was performed for 100 hours at different temperatures within the range of 100 to 1800°C. 11 obtained in this way
_Ic was measured for this superconductor under conditions of 17 Tesla, and the results shown in Figure 7 were obtained. In addition, E in the figure is
The values are shown for a superconductor of the same composition that was not heat-treated after laser beam irradiation. From the figure, it can be seen that even when heat treatment is performed only after laser beam irradiation, a heat treatment temperature of 300 to 1500°C, particularly 500 to 1000°C, is effective.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a laser irradiation device used in an embodiment of the manufacturing method of the present invention, FIG. 2 is a local perspective view of a compound superconductor manufactured by the manufacturing method of the present invention, and FIG. 7 to 7 are diagrams showing the results confirmed by each example. 1... Laser irradiation device, 2... CO ₂ laser oscillator, 3... Laser beam, 6... Vacuum container, 7
...Sample, 12...Compound superconducting layer.

Claims (1)

[Scope of Claims] 1. A first composite body made of a porous molded body or a sintered body containing at least one of a plurality of elements constituting a compound superconductor, a first step in which the composite is immersed in a melt having the remaining constituent elements to allow the melt to penetrate therethrough and then solidified to obtain a second composite; After lengthening the second composite body, the surface of the second composite body is irradiated with a laser beam at a predetermined relative speed along the longitudinal direction, and this irradiation causes the second composite body to elongate. A second step of sequentially rapidly melting the surface portion of the composite and then rapidly cooling and solidifying it to generate a compound superconducting layer in the melted and solidified portion. Method for manufacturing superconductors. 2 In the first step, the first composite is formed of a powder containing niobium as a main component, and the molten body is formed of a powder containing one or more elements selected from aluminum, germanium, and gallium as a main component. The first claim in which
A method for producing a compound superconductor as described in Section 1. 3 In the first step, the first composite is formed of a plurality of wires containing niobium as a main component,
2. The method for manufacturing a compound superconductor according to claim 1, wherein the molten material contains one or more elements selected from aluminum, germanium, and gallium as a main component. 4 The molten material in the second composite is 5% by volume.
A method for producing a compound superconductor according to claim 1, wherein the proportion is 50%. 5 In the first step, the first complex comprises a group of M (M is one metal element selected from lead, tin, copper, and silver), a sulfide of M, sulfur, molybdenum, and molybdenum sulfide. 1 selected from
The melt is formed of one or more kinds of powders selected from the above group.
A patent in which the composite is made up of components with a melting point lower than that of the first composite, and contains metal M, molybdenum, and sulfur in the composite obtained by infiltrating the first composite. Claim 1
A method for producing a compound superconductor as described in Section 1. 6 In the first step, the first composite includes powder of the metal M, powder of the sulfide of M, and a powder selected from a mixture thereof, molybdenum powder, molybdenum sulfide powder, and a powder thereof. 6. The method for manufacturing a compound superconductor according to claim 5, wherein the melt is formed of a mixture with one powder selected from the mixture and contains sulfur as a component. 7. The compound according to claim 5, wherein in the first step, the first composite is formed of molybdenum sulfide powder, and the melt contains the metal M as a component. Method for manufacturing superconductors. 8 In the first step, the first composite body is formed of a mixture of a powder selected from a sulfide powder of the metal M, a molybdenum powder, and a mixture thereof, and a molybdenum sulfide powder, and 6. The method for producing a compound superconductor according to claim 5, wherein a material containing the metal M as a component is used. 9. The method according to claim 5, wherein in the first step, the first composite body is formed of a plurality of molybdenum wires, and the melt is composed of the metal M and sulfur. Method for manufacturing compound superconductors. 10. Claims 2 to 10, wherein the first step includes a step of inserting the first composite into a niobium tube before or after infiltrating the first composite with a melt. 4. A method for producing a compound superconductor according to any one of Item 4. 11. Claims 5 to 11, wherein the first step includes a step of inserting the first composite into a molybdenum pipe before or after infiltrating the first composite with a melt. 9. A method for producing a compound superconductor according to any one of Item 9. 12. The method for manufacturing a compound superconductor according to claim 1, wherein in the second step, the power density of the laser beam is set to 10 ⁴ W/cm ² or more at the irradiation location. 13. Claim 1, wherein the second step includes a step of heat-treating the second composite at 400 to 2000°C before irradiating the second composite with a laser beam. A method for producing a compound superconductor. 14 The second step is to irradiate the second composite with a laser beam and then irradiate the second composite with a laser beam.
The method for producing a compound superconductor according to claim 1, which includes a step of heat treatment at 300 to 1500°C. 15 The first step includes the step of inserting the first composite into a niobium tube before or after infiltrating the first composite with the melt, and the second step includes the step of inserting the first composite into the niobium tube. a step of heat-treating the second composite at 400 to 2000°C before irradiating the laser beam to the composite;
A method for producing a compound superconductor according to claim 1, which comprises a step of heat treatment at 1500°C. 16 The first step includes the step of inserting the first composite into a molybdenum tube before or after infiltrating the first composite with a melt, and the second step includes the step of inserting the first composite into a molybdenum tube. Before irradiating the laser beam on the above-mentioned second complex,
℃ heat treatment step, and after irradiating the second composite with a laser beam, the second composite is
A method for producing a compound superconductor according to claim 1, which comprises a step of heat treatment at 300 to 1500°C.