An iron-based superconducting composite material and a method for producing the same

Abstract

The application provides an iron-based superconducting composite material and a preparation method thereof, and belongs to the field of superconducting materials.The application provides a preparation method of an iron-based superconducting composite material, which comprises the following steps: filling a plurality of single-core rods in a silver sheath, and then filling tin wires in the gap between the single-core rods and the silver sheath to obtain a multi-core composite ingot; the single-core rod comprises a silver tube and iron-based superconducting material preparation raw materials in the silver tube; the multi-core composite ingot is subjected to cyclic face reduction processing and intermittent annealing treatment, a silver-tin alloy layer is gradually generated, and a composite ingot containing a silver-tin alloy is obtained; the total number of annealing treatments in the intermittent annealing treatment is greater than or equal to 2; the composite ingot containing the silver-tin alloy is subjected to heat treatment to generate an iron-based superconducting material, and the iron-based superconducting composite material is obtained. The intermittent annealing treatment causes the interface diffusion of the metal sheath silver and the tin wires, and a silver-tin alloy with high tensile strength is gradually generated, so that the tensile strength of the superconducting wire is improved.

Description

Technical Field

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

[0002] Iron-based superconducting materials possess advantages such as high upper critical field, large critical current, and low anisotropy, and are considered a novel high-temperature superconducting material with significant application potential in the mid-temperature, high-magnetic-field field. Compared with niobium-based low-temperature superconducting materials, iron-based superconductors have higher critical transition temperatures and critical magnetic fields; compared with copper oxide high-temperature superconducting materials, iron-based superconductors have lower material and fabrication costs.

[0003] While the critical current density of current-carrying iron-based superconducting wires has reached practical application levels, improvements in their mechanical properties are limited by the cladding material: silver, as a cladding material, has low tensile strength and cannot meet the requirements of strong magnetic field applications. Using a composite of high-strength metals (such as Monel or stainless steel) and silver as the cladding material would affect the plastic deformation process of the composite during manufacturing, making it difficult to process and prone to causing uneven core wires. How to improve the mechanical strength of the wire without reducing its current-carrying capacity is the key and challenge for advancing the practical application of current-carrying iron-based superconducting wires. Summary of the Invention

[0004] This invention provides an iron-based superconducting composite material and its preparation method. The iron-based superconducting composite material prepared by this invention improves mechanical strength and has uniform core wire distribution without reducing current carrying capacity.

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

[0006] Several single-core rods are filled into a silver-clad sleeve, and then tin wire is filled into the gap between the single-core rods and the silver-clad sleeve to obtain a multi-core composite ingot; the single-core rods include a silver tube and the iron-based superconducting material preparation raw material in the silver tube;

[0007] The multi-core composite ingot is subjected to cyclic surface reduction processing and intermittent annealing to gradually generate a silver-tin alloy layer, thereby obtaining a composite ingot containing silver-tin alloy; the total number of annealing processes in the intermittent annealing process is ≥2;

[0008] The composite ingot containing silver-tin alloy is heat-treated to generate an iron-based superconducting material, thus obtaining the iron-based superconducting composite material.

[0009] Preferably, the chemical formula of the iron-based superconducting material is Ba. 1-x K x Fe2As2, x = 0.2 to 0.5.

[0010] Preferably, the method for preparing the single core rod includes the following steps:

[0011] The raw materials for preparing iron-based superconducting materials are mixed and then filled into a silver tube, followed by rotary forging and drawing.

[0012] Preferably, the diameter of the single core rod is 1 / 6 to 1 / 3 of the inner diameter of the silver sheath.

[0013] Preferably, the diameter of the tin wire is 1 / 37 to 1 / 18 of the inner diameter of the silver sheath.

[0014] Preferably, the total number of annealing processes is 3;

[0015] Each annealing treatment was performed independently at a temperature of 200–300°C and for a time of 30–120 min.

[0016] Preferably, each annealing process is performed between two adjacent face-reduction processes;

[0017] The composite ingot containing silver-tin alloy is annealed when the surface area reduction rate is between 30% and 60%.

[0018] Preferably, the surface reduction process includes rotary forging and drawing.

[0019] Preferably, the heat treatment temperature is 600–800°C and the time is 0.5–2 hours;

[0020] The heat treatment is performed in a protective atmosphere.

[0021] The present invention also provides an iron-based superconducting composite material prepared by the preparation method described in the above technical solution.

[0022] The addition of low-melting-point tin wire provides a wetting liquid phase during annealing, effectively removing voids between the core wires and improving their synergistic deformation ability in subsequent processing, thus contributing to a uniformly deformed core wire structure. Furthermore, the intermittent annealing process allows interfacial diffusion between the metal cladding silver and the tin wire, gradually forming a high-tensile-strength silver-tin alloy. This ensures the cladding material maintains the good plasticity of silver during processing and significantly improves the tensile strength of the final superconducting wire. By generating a high-strength silver-tin alloy layer during processing, the pure silver-superconducting core structure can be preserved, fundamentally guaranteeing the extremely high current-carrying capacity of the superconducting core wire. Therefore, the iron-based superconducting composite material prepared in this invention not only possesses a high critical current density but also exhibits significantly improved tensile strength and core wire uniformity. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the composite ingot structure in the embodiment. Detailed Implementation

[0024] This invention provides a method for preparing iron-based superconducting composite materials, comprising the following steps:

[0025] Several single-core rods are filled into a silver-clad sleeve, and then tin wire is filled into the gap between the single-core rods and the silver-clad sleeve to obtain a multi-core composite ingot; the single-core rods include a silver tube and the iron-based superconducting material preparation raw material in the silver tube;

[0026] The multi-core composite ingot is subjected to cyclic surface reduction processing and intermittent annealing to gradually generate a silver-tin alloy layer, thereby obtaining a composite ingot containing silver-tin alloy; the total number of annealing processes in the intermittent annealing process is ≥2;

[0027] The composite ingot containing silver-tin alloy is heat-treated to generate an iron-based superconducting material, thus obtaining the iron-based superconducting composite material.

[0028] This invention involves filling a silver-clad sleeve with several single-core rods, and then filling the gap between the single-core rods and the silver-clad sleeve with tin wire to obtain a multi-core composite ingot.

[0029] In this invention, the single core rod includes a silver tube and iron-based superconducting material preparation raw materials in the silver tube.

[0030] In this invention, the volume of the raw material for preparing the iron-based superconducting material is preferably 20% of the volume inside the silver tube.

[0031] In this invention, the preferred chemical formula of the iron-based superconducting material is Ba. 1-x K x Fe2As2, x = 0.2 to 0.5. In specific embodiments of the present invention, x can be 0.2, 0.3, 0.4 or 0.5.

[0032] In this invention, the method for preparing the single core rod preferably includes the following steps:

[0033] The raw materials for preparing iron-based superconducting materials are mixed and then filled into a silver tube, followed by rotary forging and drawing.

[0034] The raw materials used in the preparation are preferably elemental metals corresponding to the metal elements in iron-based superconducting materials.

[0035] In this invention, the mixing is preferably carried out in a protective atmosphere.

[0036] In this invention, the inner diameter of the silver tube is preferably 8 mm, and the outer diameter is preferably 10 mm.

[0037] In this invention, the diameter of the single core rod is preferably 1 / 6 to 1 / 3 of the inner diameter of the silver sheath. In specific embodiments of this invention, the diameter of the single core rod can be 1 / 6, 1 / 5, 1 / 4, or 1 / 3 of the inner diameter of the silver sheath. The diameter of the solder wire is preferably 1 / 37 to 1 / 18 of the inner diameter of the silver sheath. In specific embodiments of this invention, the diameter of the solder wire can be 1 / 37, 1 / 35, 1 / 32, 1 / 30, 1 / 28, 1 / 26, 1 / 24, 1 / 22, 1 / 20, or 1 / 18 of the inner diameter of the silver sheath.

[0038] After obtaining the multi-core composite ingot, the present invention performs cyclic surface reduction processing and intermittent annealing on the multi-core composite ingot to gradually generate a silver-tin alloy layer, thereby obtaining a composite ingot containing silver-tin alloy.

[0039] In this invention, the surface reduction process preferably includes rotary forging and drawing.

[0040] In this invention, during the intermittent annealing process, each annealing process is preferably performed between two adjacent reduction processes; the annealing process is preferably performed when the reduction rate of the composite ingot containing silver-tin alloy is between 30% and 60%; the total number of annealing processes is ≥2; in a specific embodiment of this invention, the number of annealing processes can be 3; in a specific embodiment of this invention, the silver tube with an inner diameter of 7mm is annealed when the diameter is reduced to 5mm, 2.5mm, and 1.2mm respectively.

[0041] In this invention, the temperature of each annealing treatment is preferably 200-300°C and the time is preferably 30-120 min. In specific embodiments of this invention, the temperature of each annealing treatment can be 200°C, 220°C, 240°C, 260°C, 280°C or 300°C, and the time can be 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 110 min or 120 min.

[0042] After obtaining the composite ingot containing silver-tin alloy, the present invention heat-treats the composite ingot containing silver-tin alloy to generate an iron-based superconducting material, thereby obtaining the iron-based superconducting composite material.

[0043] In this invention, the preferred temperature for the heat treatment is 600-800°C, and the preferred time is 0.5-2 hours. In specific embodiments of this invention, the temperature for the heat treatment can be 600°C, 650°C, 700°C, 750°C, or 800°C, and the preferred time can be 0.5 hours, 1 hour, 1.5 hours, or 2 hours.

[0044] In this invention, the heat treatment is preferably carried out in a protective atmosphere.

[0045] The present invention also provides an iron-based superconducting composite material prepared by the preparation method described in the above technical solution.

[0046] In this invention, the iron-based superconducting composite material preferably includes wires or strips.

[0047] The following detailed description of the iron-based superconducting composite material and its preparation method provided by the present invention, with reference to the embodiments, should not be construed as limiting the scope of protection of the present invention.

[0048] Figure 1 The following is a schematic diagram of the composite ingot structure in the embodiment: 1-silver tube, 2-single core rod, 3-tin wire.

[0049] Example 1

[0050] Under an Ar protective atmosphere, Ba shavings, K blocks, Fe powder, and As powder are mixed according to the chemical formula Ba 0.5 K 0.5 Ba122 superconducting precursor powder was prepared by thoroughly and uniformly mixing Fe2As2 at the indicated molar ratio. 21g of Ba122 superconducting precursor powder was loaded into a 12cm long silver tube (8mm inner diameter, 10mm outer diameter). The silver composite tube containing the mixed precursor powder was then rotary forged to 3.4mm and drawn to 2.3mm to obtain a single-core rod. Seven cleaned Φ2.3mm single-core rods were assembled into a silver sheath measuring Φ10 / Φ7×240mm. The edges that could not be completely filled with the single-core rod were filled with six Φ0.1mm tin wires to obtain a composite ingot. The composite ingot was then processed using a rotary forging-drawing process, and intermediate annealing at 200℃ for 40min was performed at Φ5, Φ2.5, and Φ1.2mm to eliminate processing stress and form a silver-tin alloy solution layer, ultimately producing a Φ0.8mm wire. The processed wire was placed in a vacuum annealing furnace, evacuated, and then filled with high-purity argon gas. The temperature was raised to 600℃ and held for 2 hours. Finally, the wire was cooled to room temperature with the furnace.

[0051] The critical current and tensile strength of the sample were measured using the standard four-wire method and tensile tests, yielding a critical current density of 1.5 × 10⁻⁶. 5 A / cm 2 Iron-based superconducting wire with a tensile strength of 350 MPa (4.2K, 10T).

[0052] Example 2

[0053] Under an Ar protective atmosphere, Ba shavings, K blocks, Fe powder, and As powder are mixed according to the chemical formula Ba 0.6 K 0.4Ba122 superconducting precursor powder was prepared by thoroughly and uniformly mixing Fe2As2 at the indicated molar ratio. 21g of Ba122 superconducting precursor powder was loaded into a 12cm long silver tube (8mm inner diameter, 10mm outer diameter). The silver composite tube containing the mixed precursor powder was then forged to 3.4mm and drawn to 2.3mm to obtain a single-core rod. Seven cleaned Φ2.3mm single-core rods were assembled into a silver sheath measuring Φ10 / Φ7×240mm. The edges that could not be completely filled with the single-core rod were filled with six Φ0.2mm tin wires to obtain a composite ingot. The composite ingot was then processed using a forging-drawing process, and intermediate annealing at 300℃ for 60min was performed at Φ5, Φ2.5, and Φ1.2mm to eliminate processing stress and form a silver-tin alloy solution layer, ultimately producing a Φ0.8mm wire. The processed wire was placed in a vacuum annealing furnace, evacuated, and then filled with high-purity argon gas. The temperature was raised to 800℃ and held for 0.5 hours. Finally, the wire was cooled to room temperature with the furnace.

[0054] The critical current and tensile strength of the sample were measured using the standard four-wire method and tensile test, yielding a critical current density of 10. 5 A / cm 2 Iron-based superconducting wire with a tensile strength of 300 MPa (4.2K, 10T).

[0055] Comparative Example 1

[0056] Under an Ar protective atmosphere, Ba shavings, K blocks, Fe powder, and As powder are mixed according to the chemical formula Ba 0.6 K 0.4 Ba122 superconducting precursor powder was prepared by thoroughly and uniformly mixing Fe2As2 at the indicated molar ratio. 21g of Ba122 superconducting precursor powder was loaded into a 12cm long silver tube (8mm inner diameter, 10mm outer diameter). The silver composite tube containing the mixed precursor powder was then rotary forged to 3.4mm and drawn to 2.3mm to obtain a single-core rod. Seven cleaned single-core rods with a diameter of Φ2.3mm were assembled into a silver sheath with dimensions of Φ10 / Φ7×240mm to obtain a composite ingot. The composite ingot was then processed using a rotary forging-drawing process, and intermediate annealing at 300℃ for 40min was performed at Φ5, Φ2.5, and Φ1.2mm to eliminate processing stress, ultimately producing a Φ0.8mm wire. The processed wire was placed in a vacuum annealing furnace, evacuated, and then filled with high-purity argon gas. The temperature was raised to 800℃ and held for 0.5h, finally cooled to room temperature with the furnace.

[0057] The critical current and tensile strength of the sample were measured using the standard four-wire method and tensile test, yielding a critical current density of 10. 5 A / cm 2 Iron-based superconducting wire with a tensile strength of 75 MPa (4.2K, 10T).

[0058] Comparative Example 2

[0059] Under an Ar protective atmosphere, Ba shavings, K blocks, Fe powder, and As powder are mixed according to the chemical formula Ba 0.5 K 0.5 Ba122 superconducting precursor powder was prepared by thoroughly and uniformly mixing Fe2As2 at the indicated molar ratio. 21g of Ba122 superconducting precursor powder was loaded into a 12cm long silver tube (8mm inner diameter, 10mm outer diameter). The silver composite tube containing the mixed precursor powder was then rotary forged to 3.4mm and drawn to 2.3mm to obtain a single-core rod. Seven cleaned Φ2.3mm single-core rods were assembled into a silver sheath measuring Φ10 / Φ7×240mm. The edges that could not be completely filled with the single-core rod were filled with six Φ0.1mm copper wires to obtain a composite ingot. The composite ingot was then processed using a rotary forging-drawing process, and intermediate annealing at 200℃ for 40min was performed at Φ5, Φ2.5, and Φ1.2mm to relieve processing stress, ultimately producing Φ0.8mm wire. The processed wire was placed in a vacuum annealing furnace, evacuated, and then filled with high-purity argon gas. The temperature was raised to 600℃ and held for 2 hours. Finally, the wire was cooled to room temperature with the furnace.

[0060] The critical current and tensile strength of the sample were measured using the standard four-wire method and tensile tests, yielding a critical current density of 1.5 × 10⁻⁶. 5 A / cm 2 Iron-based superconducting wire with a tensile strength of 100 MPa (4.2K, 10T).

[0061] Comparative Example 3

[0062] Under an Ar protective atmosphere, Ba shavings, K blocks, Fe powder, and As powder are mixed according to the chemical formula Ba 0.6 K 0.4After thoroughly and uniformly mixing Fe2As2 to obtain Ba122 superconducting precursor powder, 5% tin powder by weight of the Ba122 superconducting precursor powder was added to improve the connectivity of Ba122 superconducting grains, resulting in tin-containing Ba122 superconducting precursor powder. 21g of the tin-containing Ba122 superconducting precursor powder was loaded into a 12cm long silver tube (8mm inner diameter, 10mm outer diameter). The silver composite tube containing the mixed precursor powder was then rotary forged to 3.4mm and drawn to 2.3mm to obtain a single-core rod. Seven cleaned Φ2.3mm single-core rods were assembled into a silver sheath with dimensions of Φ10 / Φ7×240mm to obtain a composite ingot. The composite ingot was then processed using a rotary forging-drawing process, and intermediate annealing at 300℃ for 40min was performed at Φ5, Φ2.5, and Φ1.2mm to eliminate processing stress, ultimately producing Φ0.8mm wire. The processed wire was placed in a vacuum annealing furnace, evacuated, and then filled with high-purity argon gas. The temperature was raised to 800℃ and held for 0.5 hours. Finally, the wire was cooled to room temperature with the furnace.

[0063] The critical current and tensile strength of the sample were measured using the standard four-wire method and tensile test, yielding a critical current density of 10. 5 A / cm 2 Iron-based superconducting wire with a tensile strength of 75 MPa (4.2K, 10T).

[0064] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method of producing an iron-based superconducting composite material, characterized by, The method comprises the following steps: filling several single-core rods in a silver sheath, and then filling tin wires in the gap between the single-core rods and the silver sheath to obtain a multi-core composite ingot; the single-core rod comprises a silver tube and a raw material for preparing an iron-based superconducting material in the silver tube; gradually generating a silver-tin alloy layer by cyclicly reducing the surface of the multi-core composite ingot and intermittently annealing the multi-core composite ingot to obtain a composite ingot containing a silver-tin alloy; the total number of annealing in the intermittent annealing is greater than or equal to 2; performing heat treatment on the composite ingot containing the silver-tin alloy to generate the iron-based superconducting material, thereby obtaining the iron-based superconducting composite material.

2. The production method according to claim 1, characterized by, The chemical formula of the iron-based superconducting material is Ba 1- x K x Fe2As2, x = 0.2-0.

5.

3. The production method according to claim 1 or 2, characterized by, The method for preparing the single-core rod comprises the following steps: mixing the raw material for preparing the iron-based superconducting material, filling the mixed raw material into the silver tube, and then performing rotary swaging and drawing.

4. The method of claim 1, wherein, The diameter of the single-core rod is 1 / 6 to 1 / 3 of the inner diameter of the silver sheath.

5. The production method according to claim 1 or 4, characterized by, The diameter of the tin wire is 1 / 37 to 1 / 18 of the inner diameter of the silver sheath.

6. The method of claim 1, wherein, The total number of annealing is 3; The temperature of each annealing is independently 200 to 300℃, and the time of each annealing is independently 30 to 120 min.

7. The production method according to claim 1 or 6, characterized by, Each annealing is performed between two adjacent surface reduction processes. The annealing is performed when the surface reduction rate of the composite ingot containing the silver-tin alloy is 30 to 60%.

8. The preparation method according to claim 1, characterized in that, The surface reduction process comprises rotary swaging and drawing.

9. The method of claim 1, wherein the method is characterized by, The temperature of the heat treatment is 600 to 800℃, and the time of the heat treatment is 0.5 to 2 h; The heat treatment is performed in a protective atmosphere.

10. The iron-based superconducting composite material prepared by the method according to any one of claims 1 to 9.

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