A type of iron-based superconducting tape and its preparation method

Abstract

This invention relates to the field of superconducting materials, and particularly to an iron-based superconducting tape and its preparation method. The preparation method provided by this invention includes: ball milling raw materials for preparing the iron-based superconducting tape to obtain a mixture; pressing the mixture into a block material, sealing it in a feed tube, and then sintering it in a sintering furnace to obtain a precursor material; dividing the precursor material into two parts for crushing, one part being crushed into large particles with a particle size of 0.1~2mm, and the other part being crushed into small particles with a particle size of 5~50μm; mixing the large and small particles to obtain a mixed powder; controlling the large particles to account for 30%~80% of the total mass of the mixed powder; then, loading the mixed powder into a metal tube and cold-working it to obtain a tape; finally, heat-treating the tape to obtain the iron-based superconducting tape. This invention can improve the microstructure of the superconducting core, enhance superconducting performance, and achieve large-scale production.

Description

Technical Field

[0001] This invention relates to the field of superconducting materials, and in particular to an iron-based superconducting tape and its preparation method. Background Technology

[0002] Iron-based superconductors possess high transition temperatures (above the 20K liquid hydrogen temperature range), extremely high upper critical fields (determining the range of field strengths they can be applied to), and high intrinsic critical current densities (theoretically reaching 10). 7 A / cm 2 Due to their advantages such as [missing information - likely related to thermal conductivity and heat treatment], the large-scale practical application of iron-based superconductors has been a hot research topic in recent years. Currently, powder-in-tube (PIT) is a widely used method for preparing iron-based superconducting wires and tapes, offering advantages such as scalability and low cost. Preparing high-performance iron-based superconducting wires and tapes using the PIT method is an important prerequisite for promoting the practical application of iron-based superconductors. Studies have shown that density, texture, and grain size are key factors affecting the performance of iron-based superconducting wires and tapes. Hot pressing and pre-firing processes can effectively improve the microstructure of the tape and enhance its performance.

[0003] However, while hot pressing can simultaneously improve the density, texture, and grain size of the superconducting tape, its limitation to short samples restricts its application to large-scale fabrication. Pre-burning, though effective in improving grain size, wastes resources due to the annealing process, and frequent annealing softens the metal, negatively impacting superconducting tape performance. Therefore, finding a simple and energy-efficient method to improve the microstructure and performance of superconducting cores is crucial. Summary of the Invention

[0004] In view of this, the present invention provides an iron-based superconducting tape and its preparation method, which can effectively improve the microstructure of the superconducting core, enhance the superconducting performance of the iron-based superconducting tape, and enable large-scale production.

[0005] This invention provides a method for preparing iron-based superconducting tapes, comprising the following steps:

[0006] S1. The raw materials used to prepare iron-based superconducting tapes are ball-milled to obtain a mixture;

[0007] S2. The mixture is pressed into block material, sealed into a feed pipe, and then placed in a sintering furnace for sintering to obtain precursor material;

[0008] S3. The precursor material is divided into two parts for crushing. One part is crushed into large particles with a particle size of 0.1~2mm, and the other part is crushed into small particles with a particle size of 5~50μm. The large particles and small particles are mixed to obtain a mixed powder.

[0009] The large particles account for 30% to 80% of the total mass of the mixed powder;

[0010] S4. The mixed powder is loaded into a metal tube and cold-processed to obtain a strip; then, the strip is heat-treated to obtain an iron-based superconducting strip.

[0011] Preferably, in step S1, the ball milling is a drum ball mill and / or a planetary ball mill.

[0012] Preferably, in step S1, the ball milling is performed by first planetary ball milling and then drum ball milling.

[0013] Preferably, in step S2, the block material is a cylindrical material;

[0014] The diameter of the cylindrical material is 10~60mm and the thickness is 5~10mm.

[0015] Preferably, in step S2, the pressing pressure is 2~50MPa.

[0016] Preferably, in step S2, the sintering temperature is 600~1000℃ and the time is 10~40h.

[0017] Preferably, in step S4, the metal tube is at least one of Ag tube, Cu tube, and Fe tube;

[0018] The outer diameter of the metal tube is 6~10mm, and the wall thickness is 0.5~2mm.

[0019] Preferably, in step S4, the heat treatment temperature is 500~950℃ and the time is 0.5~10h.

[0020] Preferably, in step S1, the iron-based superconducting tape is BaK-122, SrK-122, CaK-1144 or BaNa-122;

[0021] In step S4, the cold working includes first processing into wire and then processing into strip; the thickness of the strip is 0.2~0.6mm.

[0022] The present invention also provides an iron-based superconducting tape prepared by the preparation method described in the above technical solution.

[0023] The preparation method provided by this invention includes: ball milling the raw materials used to prepare iron-based superconducting tape to obtain a mixture; pressing the mixture into a block material, sealing it in a feed tube, and then sintering it in a sintering furnace to obtain a precursor material; dividing the precursor material into two parts for crushing, one part being crushed into large particles with a particle size of 0.1~2mm, and the other part being crushed into small particles with a particle size of 5~50μm; mixing the large and small particles to obtain a mixed powder; controlling the large particles to account for 30%~80% of the total mass of the mixed powder; then loading the mixed powder into a metal tube and performing cold processing to obtain a tape; and then heat-treating the tape to obtain an iron-based superconducting tape. This invention controls the initial packed tube grain size and certain process conditions, enhancing the texture of the tape, increasing the grain size in the superconducting core, thereby improving the microstructure of the superconducting core and enhancing the superconducting performance of the tape. Moreover, the method of this invention is simple to operate and can be scaled up for mass production. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the large and small particles obtained in step S3 of Embodiment 1 of the present invention; wherein, Figure 1 (a) is a schematic diagram of large particles. Figure 1 (b) is a schematic diagram of small particles;

[0026] Figure 2 The X-ray diffraction pattern of the iron-based superconducting tape product obtained in Example 1 of this invention;

[0027] Figure 3 These are scanning electron microscope images of the iron-based superconducting tapes obtained in Example 1 and Comparative Example 1 of the present invention; wherein, Figure 3 (a) is a scanning electron microscope image of the iron-based superconducting tape obtained in Comparative Example 1. Figure 3 (b) is a scanning electron microscope image of the iron-based superconducting tape obtained in Example 1;

[0028] Figure 4 This is the MH curve of the iron-based superconducting tape obtained in Example 1 of the present invention;

[0029] Figure 5 The graph shows the test results of the critical current density of the iron-based superconducting tape obtained in Example 1 and Comparative Example 1 of this invention as a function of magnetic field. Detailed Implementation

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0031] In this article, the technical features described in an open-ended manner include both closed technical solutions composed of the listed features and open technical solutions that include the listed features.

[0032] The term “and / or” as used herein includes any and all combinations of one or more of the related listed items.

[0033] In this document, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when a range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0034] In this article, when referring to units for data ranges, if the unit is only followed by the right endpoint, it indicates that the units for the left and right endpoints are the same. For example, 10~60mm means that the units for the left endpoint "10" and the right endpoint "60" are both mm.

[0035] This invention provides a method for preparing iron-based superconducting tapes, comprising the following steps:

[0036] S1. The raw materials used to prepare iron-based superconducting tapes are ball-milled to obtain a mixture;

[0037] S2. The mixture is pressed into block material, sealed into a feed pipe, and then placed in a sintering furnace for sintering to obtain precursor material;

[0038] S3. The precursor material is divided into two parts for crushing. One part is crushed into large particles with a particle size of 0.1~2mm, and the other part is crushed into small particles with a particle size of 5~50μm. The large particles and small particles are mixed to obtain a mixed powder.

[0039] The large particles account for 30% to 80% of the total mass of the mixed powder;

[0040] S4. The mixed powder is loaded into a metal tube and cold-processed to obtain a strip; then, the strip is heat-treated to obtain an iron-based superconducting strip.

[0041] To further improve the performance of iron-based superconducting tapes and promote their practical application, this invention proposes a scalable fabrication method. This method, by controlling the initial grain size of the packed tube, further enhances the superconducting performance of the iron-based superconducting tape. Essentially, it improves the texture of the tape and increases the grain size in the superconducting core, thereby improving the microstructure of the superconducting core. This method is simple to operate, can further enhance the superconducting performance of the tape, and provides an effective route for the large-scale fabrication of iron-based superconducting tapes.

[0042] Regarding step S1 :

[0043] S1. The raw materials used to prepare iron-based superconducting tapes are ball-milled to obtain a mixture.

[0044] In this invention, the iron-based superconducting tape is preferably BaK-122, SrK-122, CaK-1144, or BaNa-122. The raw materials used to prepare the iron-based superconducting tape can be any known raw material formulations corresponding to the preparation of various iron-based superconducting tapes. For example, when the iron-based superconducting tape is BaK-122, the corresponding raw materials include Ba, K, Fe, and As; when the iron-based superconducting tape is SrK-122, the corresponding raw materials include Sr, K, Fe, and As; when the iron-based superconducting tape is CaK-1144, the corresponding raw materials include Ca, K, Fe, and As; and when the iron-based superconducting tape is BaNa-122, the corresponding raw materials include Ba, Na, Fe, and As.

[0045] In this invention, prior to ball milling, the raw materials used to prepare the iron-based superconducting tape are preferably first peeled and purified to obtain initial raw materials; after peeling, they can also be pulverized. Then, the raw materials are weighed according to the component ratio of the target iron-based superconducting tape to obtain the formulation. After weighing, a certain amount of K can be added to compensate for its loss during the subsequent sintering process.

[0046] In this invention, ball milling is performed after the raw materials are prepared. Preferably, the ball milling is a drum ball mill and / or a planetary ball mill, more preferably a combination of planetary ball milling followed by drum ball milling. The rotational speed of the planetary ball mill is preferably 200-500 rpm, specifically 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, etc.; the preferred grinding time is 1-10 hours, specifically 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, etc. The preferred rotational speed of the drum ball mill is 80-200 rpm, specifically 80 rpm, 90 rpm, 100 rpm, 110 rpm, 120 rpm, 130 rpm, 140 rpm, 150 rpm, 160 rpm, 170 rpm, 180 rpm, 190 rpm, 200 rpm, etc.; the preferred milling time is 1-6 hours, specifically 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, etc. Through the above ball milling, the raw materials are fully and uniformly mixed to obtain a mixture.

[0047] Regarding step S2 :

[0048] S2. The mixture is pressed into block material, sealed into a feed pipe, and then placed in a sintering furnace for sintering to obtain the precursor material.

[0049] In this invention, the block material is preferably cylindrical. The diameter of the cylindrical material is preferably 10-60 mm, specifically 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, 50 mm, 55 mm, 60 mm, etc. The thickness of the cylindrical material is preferably 5-10 mm, specifically 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, etc. In this invention, the pressing pressure is preferably 2-50 MPa, specifically 2 MPa, 5 MPa, 10 MPa, 15 MPa, 20 MPa, 25 MPa, 30 MPa, 35 MPa, 40 MPa, 45 MPa, 50 MPa, etc.

[0050] In this invention, after pressing, the resulting material is sealed into a feed tube. Preferably, the feed tube is made of stainless steel. The sealing is preferably performed by argon arc welding. The sealing is preferably carried out in a glove box.

[0051] In this invention, after the above sealing process, the sealed material tube is placed into a sintering furnace for sintering. The sintering furnace is preferably a tube furnace. The material tube is placed in the central region of the sintering furnace. The sintering is preferably carried out in a protective atmosphere. The protective atmosphere is preferably an argon atmosphere, specifically an atmosphere with flowing argon gas.

[0052] In this invention, the sintering temperature is preferably 600~1000℃, specifically 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, 900℃, 950℃, 1000℃, etc. The sintering holding time is preferably 10~40h, specifically 10h, 15h, 20h, 25h, 30h, 35h, 40h, etc. After sintering, the precursor material is obtained as a block.

[0053] Regarding step S3 :

[0054] S3. The precursor material is divided into two parts for crushing. One part is crushed into large particles with a particle size of 0.1~2mm, and the other part is crushed into small particles with a particle size of 5~50μm. The large and small particles are mixed to obtain a mixed powder.

[0055] In this invention, after obtaining the precursor material in step S2, it is divided into two parts for crushing. One part is crushed into large particles with a particle size of 0.1~2mm, specifically 0.1mm, 0.5mm, 1mm, 1.5mm, 2mm, etc. The other part is crushed into small particles with a particle size of 5~50μm, specifically 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, etc. The particle sizes mentioned above refer to the median grain size.

[0056] In this invention, after obtaining large and small particles separately, the large and small particles are mixed to obtain a mixed powder. The large particles account for 30% to 80% of the total mass of the mixed powder, specifically 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 66%, 67%, 70%, 75%, 80%, etc. This invention breaks the precursor into two parts of particles of specific different sizes and mixes them in a certain proportion. The large particles provide good texture for subsequent processing, while the small particles fill the gaps between particles and increase density. The combination of these two enhances the texture of the tape, increases the grain size in the superconducting core, and further improves the microstructure of the superconducting core, ultimately improving the texture and superconducting performance of the iron-based superconducting tape. In other words, this invention effectively controls the grain size in the iron-based superconducting tape by adjusting the initial packed particle size, successfully improving the texture and superconducting performance of the iron-based superconducting tape.

[0057] Regarding step S4 :

[0058] S4. The mixed powder is loaded into a metal tube and cold-processed to obtain a strip; then, the strip is heat-treated to obtain an iron-based superconducting strip.

[0059] In this invention, the metal tube is at least one selected from Ag, Cu, and Fe tubes. The outer diameter of the metal tube is preferably 6-10 mm, specifically 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, etc. The wall thickness of the metal tube is preferably 0.5-2 mm, specifically 0.5 mm, 1 mm, 1.5 mm, 2 mm, etc.

[0060] In this invention, after the mixed powder is loaded into a metal tube, the resulting composite metal tube is cold-worked. The cold working process includes first processing it into wire, and then processing it into strip. Preferably, the wire processing method is at least one of rotary forging, extrusion, and drawing, more preferably rotary forging followed by drawing. The diameter of the wire is preferably 1.6~2mm, specifically 1.6mm, 1.65mm, 1.7mm, 1.75mm, 1.8mm, 1.85mm, 1.9mm, 1.95mm, 2mm, etc. The strip processing method is preferably rolling. The thickness of the strip is preferably 0.2~0.6mm, specifically 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, etc.

[0061] In this invention, after being processed into a strip, it is preferably sealed into a tube. Specifically, the strip is placed into the tube, a vacuum is drawn, and the tube is sealed. The tube is preferably a glass tube.

[0062] In this invention, after the above treatment, heat treatment is performed. The preferred heat treatment temperature is 500~950℃, specifically 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, 900℃, 950℃, etc. The preferred heat treatment holding time is 0.5~10h, specifically 0.5h, 1h, 1.5h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h. After the above heat treatment, an iron-based superconducting tape product is obtained.

[0063] This invention also provides an iron-based superconducting tape prepared by the method described in the above-mentioned technical solution. This invention effectively controls the grain size in the iron-based superconducting tape, successfully improving its texture and superconducting properties.

[0064] Studies have shown that the performance of iron-based superconducting tapes is jointly regulated by density, texture, and grain size. This invention addresses the key technical bottleneck currently faced by iron-based superconducting tapes in terms of critical current density, and innovatively proposes a novel fabrication process that combines simplicity, high controllability, and high efficiency. Its main technical advantages are reflected in the following aspects:

[0065] (1) Significantly improves texture and optimizes grain orientation arrangement. The highly oriented grain boundary network effectively reduces the proportion of large-angle grain boundaries, thereby reducing the weak intergranular connection effect.

[0066] (2) Significantly enhances superconducting transport performance and current carrying capacity. Thanks to the improvement of texture and intergranular connectivity, the tape prepared by this invention exhibits significantly improved critical current density under both self-field and external magnetic field.

[0067] (3) Simplified process flow, in line with green and energy-saving concepts: Compared with traditional preparation routes, this invention significantly simplifies the operation steps. It not only reduces the dependence on high-precision equipment and stringent process conditions, but also effectively reduces energy consumption and production costs;

[0068] (4) The technology is highly scalable and has the potential for large-scale application. The design of this method takes into account the needs of transforming laboratory research into industrial production. Its simple and controllable features make it easy to integrate into the production line, paving the way for the large-scale application of iron-based superconducting tapes in high-power scenarios such as strong magnets and power transmission.

[0069] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0070] Example 1

[0071] S1. In a glove box with Ar as the protective gas, the raw materials Ba, K, Fe, and As for the iron-based superconducting tape BaK-122 are peeled and purified. Then, 20g of each material is weighed according to the nominal ratio of 0.6:0.4:2:2. An additional 20% by mass of K is weighed to compensate for losses during sintering (based on the nominal K mass ratio). The mixture is then first ball-milled (400 rpm, 10h), followed by roller ball milling (100 rpm, 5h) to obtain the final mixture.

[0072] S2. The mixture is pressed (at a pressure of 15 MPa) into cylindrical granules with a diameter of 25 mm and a thickness of 10 mm, and sealed in a stainless steel tube. Then, it is placed in the central area of ​​a tube furnace and sintered at 850°C for 30 h in a flowing Ar atmosphere to obtain a blocky precursor material.

[0073] S3. Weigh 10g of block precursor material and crush it into large particles of 1mm. Weigh 5g of precursor material and crush it into small particles of 20μm. Mix the large and small particles to obtain a mixed powder.

[0074] S4. The obtained mixed powder is loaded into a circular Ag tube with an outer diameter of 8 mm and a wall thickness of 1 mm. The composite Ag tube is then processed into a wire with a diameter of 1.93 mm by rotary forging and drawing. The wire is then rolled into a strip with a thickness of 0.3 mm. The resulting strip is placed in a glass tube, vacuumed, and sealed. It is then placed in a muffle furnace and heat-treated at 850°C for 1.5 h to obtain an iron-based superconducting strip.

[0075] Among them, the large and small particles obtained in step S3 are as follows: Figure 1 As shown, where, Figure 1 (a) is a schematic diagram of large particles. Figure 1 (b) is a schematic diagram of the small particles. The X-ray diffraction (XRD) spectrum of the iron-based superconducting tape product obtained in step S4 is as follows. Figure 2 As shown, the 00l peak of the tape is quite obvious, proving that the tape has a good c-axis texture. The scanning electron microscope (SEM) image of the iron-based superconducting tape product obtained in step S4 is shown below. Figure 3 As shown in (b), it can be seen that the tape contains a large number of lamellar grains, which are well arranged. The MH curve (i.e., the hysteresis loop of magnetization M as a function of magnetic field H) of the iron-based superconducting tape product obtained in step S4 is shown below. Figure 4 As shown, the MH hysteresis loop is relatively wide overall, with a width >1 under the conditions of 4.2K and 4T. Furthermore, the magnetic moment decreases relatively slowly with the increase of the magnetic field, indicating that the tape has excellent superconducting properties and a weak magnetic field dependence.

[0076] Example 2

[0077] S1. In a glove box with Ar as the protective gas, the raw materials Ba, K, Fe, and As for the iron-based superconducting tape BaK-122 are peeled and purified. Then, 20g of each material is weighed according to the nominal ratio of 0.6:0.4:2:2. An additional 20% by mass of K is weighed to compensate for losses during sintering (based on the nominal K mass ratio). The mixture is then first ball-milled (400 rpm, 10h), followed by roller ball milling (100 rpm, 5h) to obtain the final mixture.

[0078] S2. The mixture is pressed (at a pressure of 15 MPa) into cylindrical granules with a diameter of 25 mm and a thickness of 10 mm, and sealed in a stainless steel tube. Then, it is placed in the central area of ​​a tube furnace and sintered at 850°C for 30 h in a flowing Ar atmosphere to obtain a blocky precursor material.

[0079] S3. Weigh 6g of block precursor material and crush it into large particles of 1mm. Weigh 4g of precursor material and crush it into small particles of 20μm. Mix the large and small particles to obtain a mixed powder.

[0080] S4. The obtained mixed powder is loaded into a circular Ag tube with an outer diameter of 8 mm and a wall thickness of 1.5 mm. The composite Ag tube is then processed into a wire with a diameter of 1.93 mm by rotary forging and drawing. The wire is then rolled into a strip with a thickness of 0.3 mm. The resulting strip is placed in a glass tube, vacuumed, and sealed. It is then placed in a muffle furnace and heat-treated at 850°C for 1.5 h to obtain an iron-based superconducting strip.

[0081] Example 3

[0082] S1. In a glove box with Ar as the protective gas, the raw materials Ba, K, Fe, and As for the iron-based superconducting tape BaK-122 are peeled and purified. Then, 20g of each material is weighed according to the nominal ratio of 0.6:0.4:2:2. An additional 20% by mass of K is weighed to compensate for losses during sintering (based on the nominal K mass ratio). The mixture is then first ball-milled (400 rpm, 10h), followed by roller ball milling (100 rpm, 5h) to obtain the final mixture.

[0083] S2. The mixture is pressed (at a pressure of 15 MPa) into cylindrical granules with a diameter of 25 mm and a thickness of 10 mm, and sealed in a stainless steel tube. Then, it is placed in the central area of ​​a tube furnace and sintered at 850°C for 30 h in a flowing Ar atmosphere to obtain a blocky precursor material.

[0084] S3. Weigh 5g of block precursor material and crush it into large particles of 1mm. Weigh 5g of precursor material and crush it into small particles of 20μm. Mix the large and small particles to obtain a mixed powder.

[0085] S4. The obtained mixed powder is loaded into a circular Ag tube with an outer diameter of 8 mm and a wall thickness of 1.5 mm. The composite Ag tube is then processed into a wire with a diameter of 1.93 mm by rotary forging and drawing. The resulting Ag wire is then further composited into a circular Cu tube with an outer diameter of 4 mm and a wall thickness of 1 mm. The Cu / Ag composite wire is then further processed into a wire with a diameter of 1.89 mm by drawing. Finally, the wire is rolled into a strip with a thickness of 0.3 mm. The resulting strip is placed in a glass tube, vacuumed, and sealed. It is then placed in a muffle furnace and heat-treated at 700°C for 3 hours to obtain an iron-based superconducting tape.

[0086] Comparative Example 1

[0087] The implementation follows Example 1, except that in step S3, instead of using a combination of large and small particles, 15g of blocky precursor material is weighed and crushed into small particles of 20μm.

[0088] The final scanning electron microscope (SEM) image of the strip product is shown below. Figure 3As shown in (a), it can be seen that the grains in the strip obtained in Comparative Example 1 are smaller and more randomly arranged, unlike those in Example 1. Figure 3 (b) By comparison, it can be demonstrated that the process of the present invention can effectively enhance the texture of the strip and increase the grain size, optimize the grain orientation arrangement, and improve the microstructure of the superconducting core.

[0089] The critical current density of the strips obtained in each embodiment and comparative example was tested using the following method: the critical current density was calculated using the Bean model. The test results are shown in Table 1.

[0090] Table 1: Critical current density test results of the strips in each embodiment and comparative example

[0091]

[0092] As can be seen from the test results in Table 1, the critical current density of the strips obtained in Examples 1-3 of this invention at 4.2K under a self-field is 8.3 × 10⁻⁶. 4 A / cm 2 The critical current density at 4.2K and 5T is 13.7 × 10⁻⁶. 4 A / cm 2 The above demonstrates a relatively high critical current density. In contrast, the critical current density of the strip obtained in Comparative Example 1 is significantly lower.

[0093] The critical current density of the strip in Example 1 and Comparative Example 1 varies with the magnetic field as follows: Figure 5 As shown, the critical current density (Jc) of both Example 1 (red line) and Comparative Example 1 (black line) decreases with increasing magnetic field, consistent with the general physical properties of superconducting materials (the stronger the magnetic field, the stronger the resistance to superconducting current, and the lower the critical current density). Throughout the entire range of magnetic field variations (from approximately 0 to 70000 Oe), the red line (Example 1) is always above the black line (Comparative Example 1), demonstrating that the critical current density of Example 1 is significantly higher than that of Comparative Example 1 under any given magnetic field. In particular, under low magnetic field conditions (<5000 Oe), the Jc value of Example 1 is extremely high, rapidly reaching a peak value (approaching 34 × 10⁻⁶). 4 A / cm 2 The comparative example 1 showed a relatively low Jc value under a low magnetic field (maximum approximately 17.9 × 10⁻⁶). 4 A / cm 2 As the magnetic field increases (>5000 Oe), the two curves gradually flatten out, but the embodiment still maintains a clear advantage.

[0094] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of these embodiments are merely to aid in understanding the method and core ideas of the present invention, including the best mode, and to enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to those expressed in the claims, or if they include equivalent structural elements that are not substantially different from those expressed in the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A method for preparing an iron-based superconducting tape, characterized in that, Includes the following steps: S1. The raw materials used to prepare iron-based superconducting tapes are ball-milled to obtain a mixture; S2. The mixture is pressed into block material, sealed into a feed pipe, and then placed in a sintering furnace for sintering to obtain precursor material; S3. The precursor material is divided into two parts for crushing. One part is crushed into large particles with a particle size of 0.1~2mm, and the other part is crushed into small particles with a particle size of 5~50μm. The large particles and small particles are mixed to obtain a mixed powder. The large particles account for 30% to 80% of the total mass of the mixed powder; S4. The mixed powder is loaded into a metal tube and cold-processed to obtain a strip; then, the strip is heat-treated to obtain an iron-based superconducting strip.

2. The preparation method according to claim 1, characterized in that, In step S1, the ball milling is a drum ball mill and / or a planetary ball mill.

3. The preparation method according to claim 1 or 2, characterized in that, In step S1, the ball milling is performed by first planetary ball milling and then drum ball milling.

4. The preparation method according to claim 1, characterized in that, In step S2, the block material is a cylindrical material; The diameter of the cylindrical material is 10~60mm and the thickness is 5~10mm.

5. The preparation method according to claim 1, characterized in that, In step S2, the pressing pressure is 2~50MPa.

6. The preparation method according to claim 1, characterized in that, In step S2, the sintering temperature is 600~1000℃ and the time is 10~40h.

7. The preparation method according to claim 1, characterized in that, In step S4, the metal tube is at least one of Ag tube, Cu tube, and Fe tube; The outer diameter of the metal tube is 6~10mm, and the wall thickness is 0.5~2mm.

8. The preparation method according to claim 1, characterized in that, In step S4, the heat treatment temperature is 500~950℃ and the time is 0.5~10h.

9. The preparation method according to claim 1, characterized in that, In step S1, the iron-based superconducting tape is BaK-122, SrK-122, CaK-1144 or BaNa-122; In step S4, the cold working includes first processing into wire and then processing into strip; the thickness of the strip is 0.2~0.6mm.

10. An iron-based superconducting tape prepared by any one of claims 1 to 9.

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