Preparation method and application of niobium tri-aluminum superconducting wire doped with zinc iodide

Abstract

The application discloses a preparation method and application of a niobium tri-aluminum superconducting wire doped with zinc iodide, and relates to the technical field of superconducting materials.In the preparation process, zinc iodide is doped into Nb powder and aluminum powder, a tubular furnace is heated, the zinc iodide is decomposed into Zn and I at about 1150 DEG C, a chemical reaction occurs between I and Nb at about 1150 DEG C, and the decomposition reaction occurs to form Nb while the chemical reaction occurs, the purpose of refining Nb is achieved through the decomposition reaction, the particle size of Nb reacting with Al is reduced, and then the reaction between Nb and Al is more sufficient, in the subsequent RHQ treatment process, a more pure Nb3Al superconducting phase in a stoichiometric ratio of 76:24 is generated, and the smaller Zn particle size can be used as a nano magnetic flux pinning center, so that the superconducting performance of the prepared niobium tri-aluminum superconducting wire is improved, and the niobium tri-aluminum superconducting wire doped with zinc iodide with excellent superconducting performance is obtained.

Description

Technical Field

[0001] This invention relates to the field of superconducting materials technology, specifically to a method for preparing and applying niobium-aluminum superconducting wire doped with zinc iodide. Background Technology

[0002] Nuclear fusion power generation offers advantages such as being more environmentally friendly, more efficient, and more stable. Magnetic confinement fusion technology is currently one of the main technologies for achieving controlled nuclear fusion reactions. Currently, the primary material for large-size, high-magnetic-field, high-current magnetic confinement superconducting coils is Nb3Sn superconductor. However, large currents in strong magnetic fields generate enormous Lorentz forces, causing the current-carrying capacity of Nb3Sn superconducting wires to decrease. Therefore, superconducting magnets with even higher fields are required. Compared to Nb3Sn, Nb3Al superconducting materials have a higher superconducting transition temperature (T0). c ), Upper critical field (B irr Furthermore, Nb3Al exhibits far superior stress-strain resistance. Under the same tensile strain of 0.4%, the current-carrying capacity of Nb3Al superconducting wire decreases by approximately 10%, while that of Nb3Sn decreases by approximately 40%. Using Nb3Al superconductors to fabricate large superconducting magnets for nuclear fusion devices ensures consistent service performance and design, thus Nb3Al is considered an ideal alternative to Nb3Sn, leading to extensive research into the properties and fabrication processes of Nb3Al superconductors.

[0003] High-performance Nb3Al superconductors rely heavily on a stoichiometric Nb / Al distribution, making the preparation of Nb3Al with a molar ratio of Nb:Al = 3:1 crucial. Doping Nb3Al with other elements is an effective method to improve its superconducting properties. The preparation of Nb3Al superconducting wires mainly involves two steps: precursor wire preparation and heat treatment phase formation. Precursor wire preparation methods include powder packing, sheathing, and winding. Heat treatment phase formation mainly includes low-temperature and high-temperature heat treatment. The superconducting properties of Nb3Al are highly sensitive to heat treatment temperature; Nb3Al superconducting wires prepared below 1800℃ exhibit poor performance because the resulting Nb3Al superconducting phase deviates significantly from the stoichiometric ratio (Nb:Al = 3:1). The phase formation temperature of Nb3Al with a stoichiometric ratio is between 1940℃ and 2060℃, and its superconducting transition temperature (T0) is also crucial. c The K value exceeds 18K. However, Nb3Al prepared by existing technologies generally deviates from the stoichiometric ratio, i.e., it has low purity and poor superconductivity. Therefore, providing a Nb3Al superconductor with a stoichiometric ratio close to Nb:Al = 3:1 (molar ratio) and good superconductivity is a problem that urgently needs to be solved by existing technologies. To address the above problems, this invention proposes a method for preparing and applying niobium-aluminum superconducting wire doped with zinc iodide. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing and applying zinc iodide-doped niobium-aluminum superconducting wire. The prepared niobium-aluminum superconducting wire is a highly uniform A15 phase Nb3Al superconducting wire with a Nb:Al molar ratio close to the stoichiometric ratio of 3:1. The superconducting phase is purer, the critical current density is high, and the superconducting performance is excellent.

[0005] To achieve the above objectives, the present invention provides a method for preparing niobium-aluminum superconducting wire doped with zinc iodide, specifically comprising the following steps:

[0006] (1) In an inert atmosphere, zinc iodide powder, Nb powder and Al powder are mixed evenly to obtain a mixed powder; the mixed powder is shaped to obtain Nb / Al precursor wire doped with zinc iodide, and then the Nb / Al precursor wire doped with zinc iodide is placed in a tube furnace for heating and then kept warm.

[0007] (2) The zinc iodide-doped Nb / Al precursor wire obtained in step (1) is subjected to RHQ treatment to obtain a supersaturated solid solution Nb(Al). ss Wire;

[0008] (3) The supersaturated solid solution Nb(Al) obtained in step (2) ss The wire was subjected to low-temperature annealing to obtain niobium-aluminum superconducting wire doped with zinc iodide.

[0009] Preferably, in step (1), the molar ratio of Nb powder to Al powder is 74:26, wherein the average particle size of Nb powder is 5-45 μm and the average particle size of Al powder is 25-45 μm.

[0010] Preferably, in step (1), the mass percentage of zinc iodide in the mixed powder is 0.1% to 3%.

[0011] Preferably, in step (1), the mass percentage of zinc iodide in the mixed powder is 0.5% to 1.5%.

[0012] Preferably, in step (1), the heating temperature is 1150℃ and the holding time is 30 minutes.

[0013] Preferably, in step (1), the specific operation of the molding process is to load the mixed powder into the Nb tube and fill it tightly to obtain the Nb tube filled with powder, and then put the Nb tube filled with powder into a rotary forging machine for processing to obtain Nb / Al precursor wire doped with zinc iodide.

[0014] Preferably, in step (2), the specific operation of RHQ treatment is to apply a DC current of 100 to 220A to the zinc iodide-doped Nb / Al precursor wire, heat the zinc iodide-doped Nb / Al precursor wire to 2000°C within 2 to 10 seconds, and then quench it to 50°C.

[0015] Preferably, in step (3), the temperature of the low-temperature annealing is 790-820°C and the time of the low-temperature annealing is 8-11 hours.

[0016] The present invention also provides a zinc iodide-doped niobium-aluminum superconducting wire prepared by the above preparation method.

[0017] The present invention also provides the application of the zinc iodide-doped niobium-aluminum superconducting wire prepared above in superconducting magnets.

[0018] This invention places Nb / Al precursor wire doped with zinc iodide in a tube furnace. At 1150°C, zinc iodide decomposes into iodine and fine zinc particles. Nb reacts with iodine, decomposing as it reacts, generating Nb particles with even smaller diameters. These smaller Nb particles react more fully with Al during RHQ treatment, while the smaller Zn particles act as pinning centers, improving the superconducting properties of the wire.

[0019] The preparation method provided by this invention involves doping Nb with zinc iodide during the preparation process. Specifically, a zinc iodide-doped Nb / Al precursor wire is first prepared. ZnI2 decomposes into I2 and Zn at 1150℃. I and Nb then undergo a combination reaction at approximately 1150℃: Nb + 2I2 → NbI4. This process involves both combination and decomposition reactions to form Nb. The Nb generated through the decomposition reaction refines the Nb, reducing the particle size of the Nb that reacts with Al. During RHQ treatment (rapid heating and cooling), the reaction between Nb and Al becomes more complete, generating a purer Nb3Al superconducting phase with a stoichiometric ratio of 76:24. This improves the superconducting performance of the prepared niobium-aluminum superconducting wire, resulting in a zinc iodide-doped niobium-aluminum superconducting wire with a high superconducting transition temperature and excellent superconducting properties. The stoichiometric ratio of Nb to Al in the zinc iodide-doped niobium-aluminum superconducting wire prepared by this invention is close to 74:26, and its critical current density J c (A / cm 2 It reached 3.67 × 10 at 8T. 4 A / cm 2 It exhibits excellent superconducting properties.

[0020] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0021] Figure 1 A scanning electron microscope image of the zinc iodide-doped niobium-aluminum superconducting wire prepared in Example 1 of the present invention;

[0022] Figure 2 The critical current density J of the zinc iodide-doped niobium-aluminum superconducting wire prepared in Example 1 of this invention. c (A / cm2 Trend graph of magnetic field strength H(T) changing. Detailed Implementation

[0023] This invention provides a method for preparing niobium-aluminum superconducting wire doped with zinc iodide, specifically including the following steps:

[0024] (1) In an inert atmosphere, zinc iodide powder, Nb powder, and Al powder are mixed evenly to obtain a mixed powder. The mixed powder is then shaped to obtain Nb / Al precursor wire doped with zinc iodide. The Nb / Al precursor wire doped with zinc iodide is then placed in a tube furnace and heated at 1150°C for 30 minutes. At this heating temperature, zinc iodide decomposes into iodine and fine zinc particles. Nb reacts with iodine, decomposing as it reacts, to generate Nb particles with even smaller diameters.

[0025] (2) The zinc iodide-doped Nb / Al precursor wire obtained in step (1) is subjected to RHQ treatment to obtain a supersaturated solid solution Nb(Al). ss Wire.

[0026] (3) The supersaturated solid solution Nb(Al) obtained in step (2) ss The wire was subjected to low-temperature annealing to obtain niobium-aluminum superconducting wire doped with zinc iodide.

[0027] In this invention, the inert atmosphere is preferably argon.

[0028] In this invention, the average particle size of Nb powder is preferably 5–45 μm, and the average particle size of Al powder is preferably 25–45 μm. This invention controls the average particle sizes of Nb powder and Al powder within the above range to promote uniform mixing and subsequent full reaction, which is beneficial for generating a purer Nb3Al superconducting phase that better conforms to the stoichiometric ratio of 76:24. This improves the superconducting performance of the prepared niobium-aluminum superconducting wire, resulting in a zinc iodide-doped niobium-aluminum superconducting wire with high superconducting transition temperature and excellent superconducting performance.

[0029] In this invention, the preferred molar ratio of Nb powder to Al powder is 74:26. ​​This invention controls the molar ratio of Nb powder to Al powder within the above range to avoid Al atom loss during the preparation process, which facilitates the formation of a purer Nb3Al superconducting phase that better conforms to the stoichiometric ratio of 76:24, thereby improving the superconducting performance of the prepared niobium-aluminum superconducting wire.

[0030] In this invention, the purity of the zinc iodide powder, Nb powder, and Al powder is preferably >99.9% independently.

[0031] In this invention, the mass percentage of zinc iodide in the mixed powder is preferably 0.1-3%, more preferably 0.5-1.5%. This invention controls the mass percentage of zinc iodide in the mixed powder within the above range. Zinc iodide decomposes into iodine and zinc at 1150℃. Since iodine is highly prone to sublimation, and the reaction between iodine and Nb is simultaneous reaction and decomposition, excessive doping (greater than 1.5%) will cause zinc iodide to decompose during heating in a tube furnace, resulting in a large amount of iodine sublimating and escaping, causing numerous cracks on the wire surface and affecting subsequent experimental progress.

[0032] In this invention, the forming process includes loading the mixed powder into an Nb tube and filling it tightly to obtain an Nb tube filled with powder, and then placing the Nb tube filled with powder into a rotary forging machine for processing to obtain an Nb / Al precursor wire doped with zinc iodide.

[0033] The present invention does not impose any special restrictions on the method of placing the Nb tube containing the powder into a rotary forging machine for processing. Any technical solution known in the art can be used to obtain Nb / Al precursor wire doped with zinc iodide.

[0034] In this invention, the RHQ treatment preferably includes applying a DC current of 100-220A to the zinc iodide-doped Nb / Al precursor wire, heating the zinc iodide-doped Nb / Al precursor wire to about 2000°C within 2-10 seconds, and then rapidly quenching it to 50°C.

[0035] This invention controls the DC current, heating temperature, and rapid quenching temperature in the RHQ process within the above-mentioned range. The current is set to 200A (based on the measured resistance of the wire and experimental results, if the current is too low, the temperature cannot reach 2000℃, and if it is too high, it will cause the wire to explode). The temperature is raised to about 2000℃ (above 1900℃, Nb / Al will react instantaneously to form Nb3Al superconductor, and Nb3Al crystals will grow rapidly at high temperatures). The gallium liquid is rapidly quenched at about 50℃. The cold quenching can generate a bcc phase supersaturated solid solution Nb(Al)ss and the generated A15 phase crystals are small.

[0036] In this invention, the temperature of the low-temperature annealing is preferably 790–820°C, more preferably 800°C. The time of the low-temperature annealing is preferably 8–11 hours, more preferably 10 hours.

[0037] This invention also provides a zinc iodide-doped niobium-aluminum superconducting wire prepared by the preparation method described above, comprising a niobium-aluminum superconducting phase. The final wire contains very little iodine because a large amount of the decomposed iodine escapes after the reaction in the tube furnace.

[0038] The present invention also provides the application of the zinc iodide-doped niobium-aluminum superconducting wire described above in superconducting magnets.

[0039] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the invention should be considered equivalent substitutions and are included within the scope of protection of the present invention. Furthermore, it should be understood that after reading the contents of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims and are all within the scope of protection of the present invention.

[0040] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The term "embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment, nor does it specifically limit its independence or connection with other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the technical features mentioned in each embodiment can be combined in any way to form corresponding implementable technical solutions.

[0041] Unless otherwise defined, the technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the use of related terms herein is merely for the purpose of describing particular embodiments and is not intended to limit this application.

[0042] Unless otherwise specified, the reagents, instruments, and equipment used in this invention are all commonly used by those skilled in the art, and are all commercially available products that can be purchased through commercial channels.

[0043] Example 1

[0044] This embodiment provides a method for preparing niobium-aluminum superconducting wire doped with zinc iodide. The specific preparation steps are as follows:

[0045] (1) Under argon protection, Nb powder (average particle size of 45 μm), Al powder (average particle size of 45 μm) and ZnI2 powder were weighed and mixed evenly by planetary ball milling to obtain 13 g of mixed powder;

[0046] The zinc iodide powder accounts for 1% of the mass of the mixed powder. To avoid Al atom loss during the preparation process, the molar ratio of Nb powder to Al powder is 74:26. ​​The purity of all powders is above 99.9%.

[0047] Under argon protection, the mixed powder is loaded into an Nb tube and filled tightly to obtain an Nb tube filled with powder. The Nb tube filled with powder is then placed into a rotary forging machine for processing to obtain an Nb / Al precursor wire with a diameter of 1.6 mm doped with zinc iodide.

[0048] (2) Cut the zinc iodide-doped Nb / Al precursor wire obtained in step (1) into short wires of 10-15cm in length. The short wires are heated in a tube furnace at 1050°C for 30 minutes and then subjected to RHQ loading onto a static heat treatment device. A DC current of 200A is applied and the zinc iodide-doped Nb / Al precursor wire is heated to 2000°C within <10s. Then, it is immediately quenched to 50°C in a room temperature liquid Ga pool to obtain a supersaturated solid solution Nb(Al)ss wire.

[0049] (3) The supersaturated solid solution Nb(Al) obtained in step (2) ss The wire was subjected to low-temperature heat treatment at 800℃ for 10 hours to obtain niobium-aluminum superconducting wire doped with zinc iodide.

[0050] The microstructure and superconducting properties of the zinc iodide-doped niobium-aluminum superconducting wire prepared in this embodiment were tested.

[0051] 1. The zinc iodide-doped niobium-aluminum superconducting wire prepared in this embodiment was observed using a scanning electron microscope, and the resulting scanning electron micrograph is shown below. Figure 1 As shown. By Figure 1 It can be seen that the stoichiometric ratio of Nb to Al in the zinc iodide-doped niobium-aluminum superconducting wire prepared in this embodiment is close to 74:26.

[0052] 2. The critical current density J of the zinc iodide-doped niobium-aluminum superconducting wire prepared in this embodiment was determined using the PPMS-VSM method. c (A / cm 2 The trend of change with magnetic field H(T) is shown in the figure below. Figure 2 As shown. By Figure 2 As can be seen, the critical current density J of the zinc iodide-doped niobium-aluminum superconducting wire prepared in this embodiment is... c (A / cm 2 It reached 3.67 × 10 at 8T. 4 A / cm 2 It exhibits excellent superconducting properties.

[0053] In summary, the stoichiometric ratio of Nb to Al in the zinc iodide-doped niobium-aluminum superconducting wire prepared by this invention is close to 74:26, and its critical current density J at 4.2K is [missing value]. c (A / cm 2 It reached 3.67 × 10 at 8T. 4 A / cm2 The critical current density is higher than that of the pure sample, and the superconducting performance is excellent.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a zinc iodide-doped niobium-aluminum superconducting wire, characterized in that, Specifically, the following steps are included: (1) In an inert atmosphere, zinc iodide powder, Nb powder and Al powder are mixed evenly to obtain a mixed powder; the mixed powder is shaped to obtain Nb / Al precursor wire doped with zinc iodide, and then the Nb / Al precursor wire doped with zinc iodide is placed in a tube furnace for heating and then kept warm. The molar ratio of Nb powder to Al powder is 74:26; The mass percentage of zinc iodide in the mixed powder is 0.1%~3%; The heating temperature is 1150℃, and the holding time is 30 minutes. (2) The zinc iodide-doped Nb / Al precursor wire obtained in step (1) is subjected to RHQ treatment to obtain a supersaturated solid solution Nb(Al). ss Wire; (3) The supersaturated solid solution Nb(Al) obtained in step (2) ss The wire was subjected to low-temperature annealing to obtain niobium-aluminum superconducting wire doped with zinc iodide.

2. The method for preparing a zinc iodide-doped niobium-aluminum superconducting wire according to claim 1, characterized in that: In step (1), the average particle size of Nb powder is 5~45μm, and the average particle size of Al powder is 25~45μm.

3. The method for preparing a zinc iodide-doped niobium-aluminum superconducting wire according to claim 1, characterized in that: In step (1), the mass percentage of zinc iodide in the mixed powder is 0.5~1.5%.

4. The method for preparing a zinc iodide-doped niobium-aluminum superconducting wire according to claim 1, characterized in that: In step (1), the specific operation of the molding process is to load the mixed powder into the Nb tube and fill it tightly to obtain the Nb tube filled with powder, and then put the Nb tube filled with powder into a rotary forging machine for processing to obtain Nb / Al precursor wire doped with zinc iodide.

5. The method for preparing a zinc iodide-doped niobium-aluminum superconducting wire according to claim 1, characterized in that: In step (2), the specific operation of RHQ treatment is to apply a DC current of 100~220 A to the zinc iodide-doped Nb / Al precursor wire, heat the zinc iodide-doped Nb / Al precursor wire to 2000℃ within 2~10s, and then quench it to 50℃.

6. The method for preparing a zinc iodide-doped niobium-aluminum superconducting wire according to claim 1, characterized in that: In step (3), the temperature of low-temperature annealing is 790~820℃, and the time of low-temperature annealing is 8~11h.

7. A niobium-aluminum superconducting wire doped with zinc iodide, characterized in that: The superconducting wire is prepared by the preparation method described in any one of claims 1-6.

8. The niobium-aluminum superconducting wire doped with zinc iodide according to claim 7, characterized in that: The superconducting wire is used in superconducting magnets.

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