Iron-based superconducting tape cooked powder and preparation method thereof

Abstract

The invention belongs to the technical field of superconducting, and particularly relates to iron-based superconducting tape cooked powder and a preparation method thereof. The preparation method comprises the following steps: S1, mixing raw materials of the iron-based superconducting tape, and then mechanically pressing to obtain a green body; s2, separating the green body by adopting an isolating layer, sintering and crushing to obtain the iron-based superconductive cooked powder, wherein the material of the isolating layer comprises a high-temperature inert material; the isolating layer is provided with through holes, the porosity of the isolating layer is 50-95%, and the average aperture size of the through holes is 2-25 mm; the sintering temperature ranges from 800 DEG C to 1200 DEG C, and the sintering time ranges from 10 h to 50 h; the preparation method disclosed by the invention is simple and high in operability; mechanical pressing can simplify operation, save time, eliminate interference of human factors and ensure process stability and repeatability; and the prepared cooked powder is good in quality and batch stability.

Description

Technical Field

[0001] The invention belongs to the technical field of superconductivity, and in particular relates to an iron-based superconducting tape powder and a preparation method thereof. Background Art

[0002] Iron-based superconducting materials are a new type of high-temperature superconducting materials. Compared with traditional superconducting materials, iron-based superconducting materials have the advantages of high upper critical field, low anisotropy, high critical transmission current, low dependence on strong magnetic field, and simple preparation process, and have attracted widespread attention.

[0003] Among the many systems of iron-based superconducting materials, the "122" system tape has a high critical current density and is prepared using the powder-in-tube method (PIT), which has a relatively low cost and is the main direction of current research. The PIT method is to load the sintered iron-based superconducting precursor powder into a metal tube with excellent workability and thermal conductivity, and prepare it into a superconducting tape through drawing, rolling and other processing processes. The superconducting core in the tape is then subjected to vacuum heat treatment to complete the transformation to the superconducting phase. High-quality superconducting cooked powder is an important basis for the preparation of tapes by the powder-in-tube method, and determines the upper limit of the final tape current-carrying performance. Achieving the synthesis of higher yields of cooked powder is the only way for iron-based superconducting materials to be practical.

[0004] Currently, the solid-phase sintering method is used to produce "122" iron-based superconducting cooked powder. After thoroughly mixing the required elements in stoichiometric proportions, the mixed powder is placed into a metal tube that is non-reactive with the raw materials. Both ends are sealed with cylindrical metal blocks of the same material. This metal tube is then placed into a larger stainless steel tube and welded shut with stainless steel discs. Finally, the tightly packed powder, protected by a double metal seal, is placed in a heating furnace for sintering. This method is not only lengthy and complex, but also inefficient, and the cost of metals inert to the raw powder is high. The packed raw powder relies on manual compaction, which can introduce errors and makes stable and repeatable results difficult. Furthermore, sintering easily leads to oxidation, resulting in suboptimal quality of the cooked powder. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defects of the existing cooked powder preparation method, which is complex, has a long process, is inefficient, and has poor quality and batch stability of the prepared cooked powder, thereby providing an iron-based superconducting tape cooked powder and a preparation method thereof.

[0006] To this end, the present invention provides the following technical solutions:

[0007] A first aspect of the present invention provides a method for preparing an iron-based superconducting tape powder, wherein the preparation method comprises the following steps:

[0008] S1, mixing raw materials of the iron-based superconducting tape and mechanically pressing the mixture to obtain a green body;

[0009] S2, separating the green body with an isolation layer, sintering, and crushing to obtain iron-based superconducting cooked powder;

[0010] Wherein, the material of the isolation layer includes a high-temperature inert material;

[0011] The isolation layer has through holes, the porosity of the isolation layer is 50-95%, and the average pore size of the through holes is 2-25 mm;

[0012] The sintering temperature is 800-1200° C. and the sintering time is 10-50 hours.

[0013] In the present invention, the raw materials of the iron-based superconducting tape are conventional materials in the art, and the raw materials can be in the form of blocks or powders. Typically, but not limited to, in an inert atmosphere glove box, according to A 1-x B x The stoichiometric ratio of Fe2As2 (A includes Ba and / or Sr, B includes K and / or Na, 0<x<1) is adopted, and the corresponding elements are weighed and added, including barium block (purity ≥99.9%), strontium block (purity ≥99.9%), potassium block (purity ≥99.9%), sodium block (purity ≥99.9%), iron powder (purity ≥99.9%), and arsenic powder (purity ≥99.9%).

[0014] In the present invention, high-temperature inert materials refer to a type of material that can maintain chemical stability and is not easy to react with other substances in a high-temperature environment (usually hundreds of degrees Celsius to thousands of degrees Celsius), and has good thermal stability and mechanical properties; in the present invention, the high-temperature inert material is a conventional high-temperature inert material in this field. Typically, but not limiting, the high-temperature inert material includes metals and / or ceramics, optionally including tungsten element, niobium element, molybdenum element, titanium element, tantalum element, heat-resistant alloys (iron-based high-temperature alloys, nickel-based high-temperature alloys, cobalt-based high-temperature alloys), and alumina ceramics.

[0015] In the present invention, the mixing method is a conventional mixing method in the art, as long as the mixing is uniform. Typically, but not limited to, ball milling is used for mixing.

[0016] In the present invention, mechanical compression is performed using a tablet press and a tablet pressing mold. Typically, but not limited to, the tablet pressing mold is cylindrical.

[0017] In the present invention, the separated green bodies are placed in a crucible, and then the crucible is placed in a stainless steel tube, and both ends are welded and sealed. All of these operations are performed under a protective gas. The protective gas is a conventional gas in the art, typically, but not limited to, argon.

[0018] In the present invention, the crushing is a conventional method in the art, and typically, but not limitedly, the crushing includes grinding.

[0019] In some optional embodiments, the porosity of the isolation layer is 50-95%, and the average pore size of the through-holes is 2-25 mm; as an example, the porosity of the isolation layer is 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%; or is within the range of any of the above values; as an example, the average pore size of the through-holes is 2 mm, 5 mm, 7 mm, 12 mm, 15 mm, 19 mm, 22 mm, 24 mm, 25 mm; or is within the range of any of the above values.

[0020] In the present invention, the average pore size refers to the average value of the diameters of the pores.

[0021] In some optional embodiments, the porosity of the isolation layer is 80-90%, and the average pore size of the through holes is 8-12 mm.

[0022] In some optional embodiments, the mechanical pressing pressure is 50-220 MPa, and the time is 1-10 min. As an example, the mechanical pressing pressure is 50 MPa, 60 MPa, 80 MPa, 90 MPa, 120 MPa, 150 MPa, 180 MPa, 200 MPa, 220 MPa, or within a range thereof; as an example, the time is 1 min, 3 min, 5 min, 7 min, 10 min, or within a range thereof.

[0023] In some optional embodiments, the mechanical pressing pressure is 80-120 MPa and the time is 3-5 min.

[0024] In some optional embodiments, the sintering temperature is 900-1100° C., and the sintering time is 20-30 hours.

[0025] In some optional embodiments, the isolation layer is processed from a high-temperature inert material into a circular plate with holes.

[0026] In some optional embodiments, the thickness of the isolation layer is 3-6 mm.

[0027] In some optional embodiments, the mixing speed is 200-500 r / min and the mixing time is 5-10 h.

[0028] In some optional embodiments, the blank is cylindrical with a diameter of 15-70 mm and a height of 2-10 mm.

[0029] The second aspect of the present invention protects an iron-based superconducting tape powder prepared by the above-mentioned preparation method.

[0030] In the present invention, the iron-based superconducting tape powder is prepared into the iron-based superconducting tape according to conventional preparation methods in the art. Typically, but not limitedly, the powder is loaded into a metal tube and then subjected to swaging, drawing, and rolling in sequence to obtain the iron-based superconducting tape.

[0031] The technical solution of the present invention has the following advantages:

[0032] 1. The present invention provides a method for preparing iron-based superconducting tape powder, wherein the preparation method comprises the following steps: S1, mixing the raw materials of the iron-based superconducting tape and mechanically pressing them to obtain a green body; S2, separating the green body with an isolation layer, sintering, and crushing them to obtain iron-based superconducting powder; wherein the material of the isolation layer comprises a high-temperature inert material; the isolation layer has through holes, the porosity of the isolation layer is 50-95%, and the average pore size of the through holes is 2-25 mm; the sintering temperature is 800-1200°C, and the sintering time is 10-50 hours; the preparation method of the present invention is simple and has strong operability; in step S1, Mechanical pressing can simplify the operation and save time compared with manual compaction of raw materials. Mechanical pressing eliminates the interference of human factors and ensures process stability and repeatability. In step S2, an isolation layer with a specific pore structure is used to separate the green body to ensure that the vapor pressure generated by the volatilization of elements in the green body during the sintering process at a specific temperature can diffuse and react evenly, promote chemical reactions during the sintering process, increase the superconducting phase content, and reduce impurities. The presence of through holes can make the sintering more complete. At the same time, the isolation layer with a specific pore structure uses less isolation layer material than the non-porous isolation layer material, and can also reduce the cost of the isolation layer.

[0033] 2. The specific pore structure of the isolation layer of the present invention can further improve the efficiency of diffusion of volatile elements while maintaining the isolation layer stable and free from deformation.

[0034] 3. The specific conditions of mechanical pressing in the present invention can further ensure that the green body has a suitable density, so that during sintering, the vapor pressure generated by the volatilization of elements in the green body can further diffuse and react evenly.

[0035] 4. The specific sintering conditions of the present invention can ensure that the reaction proceeds fully while preventing the superconducting phase from decomposing due to high temperature. DETAILED DESCRIPTION

[0036] The following examples are provided for a better understanding of the present invention and are not intended to limit the best mode of implementation. They do not limit the content and scope of protection of the present invention. Any product identical or similar to the present invention obtained by anyone under the guidance of the present invention or by combining the features of the present invention with other prior arts shall fall within the scope of protection of the present invention.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are for the purpose of describing specific embodiments only and are not intended to limit this application; the terms "including" and "having" and any variations thereof in this application text are intended to cover non-exclusive inclusions.

[0038] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0039] The "range" disclosed in this application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The range defined in this way can be inclusive or exclusive of the end values ​​and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. In this application, unless otherwise specified, the numerical range "ab" represents an abbreviation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed herein, and "0-5" is just an abbreviation of these numerical combinations. In addition, when stating that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter can be, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0040] In the description of the embodiments of the present application, the term "and / or" is merely a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent three situations: A exists alone, A and B exist at the same time, and B exists alone.

[0041] In the description of the embodiments of the present application, the term "at least one" refers to one or more than two (including two).

[0042] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in this field can be used. If the manufacturer of the reagents or instruments is not specified, they are all commercially available conventional reagents.

[0043] Barium block: purity ≥99.9%;

[0044] Potassium block: purity ≥99.9%;

[0045] Iron powder: purity ≥99.9%;

[0046] Arsenic powder: purity ≥99.9%.

[0047] The purity of argon is 99.999%;

[0048] Tablet press: Tianjin Leinuoxinda Technology Co., Ltd. (NL-40T);

[0049] Cylindrical tableting mold: 30mm in diameter and 6mm in height;

[0050] Examples and Comparative Examples Among them, A is the outer diameter, B is the wall thickness, and C is the length.

[0051] Example 1

[0052] This embodiment provides a method for preparing iron-based superconducting tape powder, comprising the following steps:

[0053] S1, according to Ba 1-x K x The raw materials were prepared by weighing barium blocks, potassium blocks, iron powder and arsenic powder in the stoichiometric ratio of Fe2As2 (x = 0.4), ball milling was performed at a speed of 500 r / min for 10 h, and mechanical pressing was performed at a pressure of 120 MPa for 3 min to obtain a green body;

[0054] S2, using three isolation layers to separate the four blanks, wherein the isolation layer is made of niobium, with a porosity of 90% and an average pore size of 8mm; under argon protection, the four separated blanks are placed in Place the crucible in the The two ends of the stainless steel tube were welded and sealed, and the welded stainless steel tube was placed in a heating furnace for sintering at a temperature of 900°C for 30 hours; in an argon glove box, the stainless steel tube was cut open and the sintered product was ground to obtain iron-based superconducting cooked powder.

[0055] Example 2

[0056] This embodiment provides a method for preparing iron-based superconducting tape powder, comprising the following steps:

[0057] S1, according to Ba 1-x K x The raw materials were prepared by weighing barium blocks, potassium blocks, iron powder and arsenic powder in the stoichiometric ratio of Fe2As2 (x = 0.5), ball milling was performed at a speed of 200 r / min for 10 h, and mechanical pressing was performed at a pressure of 80 MPa for 5 min to obtain a green body;

[0058] S2, using three isolation layers to separate the four blanks, wherein the isolation layer is made of molybdenum, with a porosity of 80% and an average pore size of 12 mm; under argon protection, the four separated blanks are placed in Place the crucible in the The two ends of the stainless steel tube were sealed by welding, and the sealed stainless steel tube was placed in a heating furnace for sintering at a temperature of 1100°C for 20 hours; in an argon glove box, the stainless steel tube was cut open and the sintered product was ground to obtain iron-based superconducting cooked powder.

[0059] Example 3

[0060] This embodiment provides a method for preparing iron-based superconducting tape powder, comprising the following steps:

[0061] The method is the same as in Example 1, except that the porosity of the isolation layer is 70% and the average pore size is 15 mm.

[0062] Example 4

[0063] This embodiment provides a method for preparing iron-based superconducting tape powder, comprising the following steps:

[0064] The method of Example 1 was followed, except that the pressing pressure was 60 MPa and the pressing time was 1 min.

[0065] Comparative Example 1

[0066] This comparative example provides a method for preparing iron-based superconducting tape powder, comprising the following steps:

[0067] The method of Example 1 is the same as that of Example 1, except that in step S1, after ball milling, the powder is taken out and loaded into In the titanium tube, under the protection of argon, the raw powder was continuously compacted with a stainless steel round rod with a diameter of 9.5 mm, and both ends were Copper pillar sealing;

[0068] S2, place the titanium tube directly on The two ends of the stainless steel tube are sealed by welding, and the sealed stainless steel tube is placed in a heating furnace and sintered according to the conditions of Example 1.

[0069] Comparative Example 2

[0070] This comparative example provides a method for preparing iron-based superconducting tape powder, comprising the following steps:

[0071] The method of Example 1 is the same as that of Example 1. The difference is that in step S2, four blanks are placed in an overlapping manner under the protection of argon gas. Place the crucible in the The two ends of the stainless steel tube were welded and sealed, and the welded stainless steel tube was placed in a heating furnace for sintering at a temperature of 900°C for 30 hours; in an argon glove box, the stainless steel tube was cut open and the sintered product was ground to obtain iron-based superconducting cooked powder.

[0072] Comparative Example 3

[0073] This comparative example provides a method for preparing iron-based superconducting tape powder, comprising the following steps:

[0074] The method of Example 3 is the same, except that the porosity of the isolation layer is 48% and the average pore size is 20 mm.

[0075] Comparative Example 4

[0076] This comparative example provides a method for preparing iron-based superconducting tape powder, comprising the following steps:

[0077] The method of Example 3 is the same, except that the porosity of the isolation layer is 98% and the average pore size is 2 mm.

[0078] Comparative Example 5

[0079] This comparative example provides a method for preparing iron-based superconducting tape powder, comprising the following steps:

[0080] The method of Example 3 is the same, except that the sintering temperature is 700° C. and the sintering time is 30 h.

[0081] Comparative Example 6

[0082] This comparative example provides a method for preparing iron-based superconducting tape powder, comprising the following steps:

[0083] The method of Example 3 is the same, except that the sintering temperature is 1300° C. and the sintering time is 10 h.

[0084] Comparative Example 7

[0085] This comparative example provides a method for preparing iron-based superconducting tape powder, comprising the following steps:

[0086] The method of embodiment 3 is the same, except that the material of the isolation layer is iron.

[0087] Test Case

[0088] Testing the quality of cooked iron-based superconducting tape powder: Using a Magnetic Property Measurement System (MPMS, manufactured by Quantum Design, USA, Model MPMS3), the cooked powder's magnetization intensity (MH) is measured as a function of the background magnetic field. This system obtains a magnetic moment signal, M, for the cooked powder at a background magnetic field of 4 Tesla. The magnitude of M represents the strength of the cooked powder's ferromagnetism. A weak ferromagnetic signal (0 < M ≤ 2) indicates low impurities and good quality; a strong ferromagnetic signal (M > 2) indicates high impurities and poor quality.

[0089] Testing the batch stability of iron-based superconducting tape powder: Four samples were uniformly taken at different depths within the crucible from the same embodiment and comparative example. The ferromagnetic signal M of these four blanks was then measured, and the coefficient of variation (CV) was calculated using the formula CV = (standard deviation / mean) × 100%. The smaller the CV, the better the batch stability.

[0090] Specific test data are shown in Table 1;

[0091] Table 1 Quality of iron-based superconducting tape powder

[0092]

[0093] The iron-based superconducting tape is prepared from cooked powder. The preparation method includes the following steps: the cooked powder is loaded into a metal tube and then subjected to rotary forging, drawing and rolling in sequence.

[0094] Testing method for critical current density of iron-based superconducting tape: The critical current density is tested using the "four-lead method" at 4.2K and 10T.

[0095] Specific test data are shown in Table 2;

[0096] Table 2 Critical current density of iron-based superconducting tapes

[0097] <![CDATA[Critical current density (A / cm 2 )]]> Example 1 <![CDATA[8×10 4 ]]> Example 2 <![CDATA[7.5×10 4 ]]> Example 3 <![CDATA[6.2×10 4 ]]> Example 4 <![CDATA[7.2×10 4 ]]> Comparative Example 1 <![CDATA[3×10 4 ]]> Comparative Example 2 <![CDATA[1.2×10 3 ]]> Comparative Example 3 <![CDATA[4.5×10 3 ]]> Comparative Example 4 <![CDATA[1.8×10 4 ]]> Comparative Example 5 <![CDATA[1×10 4 ]]> Comparative Example 6 <![CDATA[3.6×10 3 ]]> Comparative Example 7 <![CDATA[2.4×10 2 ]]>

[0098] In step S1 of the preparation method of the present invention, mechanical pressing is adopted, which can simplify the operation and save time compared with manual compaction of raw materials. Mechanical pressing eliminates the interference of human factors and ensures process stability and repeatability. In step S2, an isolation layer with a specific pore structure is used to separate the green body to ensure that the vapor pressure generated by the volatilization of elements in the green body during the sintering process at a specific temperature can diffuse and react evenly, promote chemical reactions during the sintering process, increase the superconducting phase content, and reduce impurities. In addition, the presence of through holes can make the sintering more complete. At the same time, the isolation layer with a specific pore structure uses less isolation layer material than the non-porous isolation layer material, and can also reduce the cost of the isolation layer.

[0099] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for preparing iron-based superconducting tape powder, characterized in that: The preparation method comprises the following steps: S1, mixing raw materials of the iron-based superconducting tape and mechanically pressing the mixture to obtain a green body; S2, separating the green body with an isolation layer, sintering, and crushing to obtain iron-based superconducting cooked powder; Wherein, the material of the isolation layer includes a high-temperature inert material; The isolation layer has through holes, the porosity of the isolation layer is 50-95%, and the average pore size of the through holes is 2-25 mm; The sintering temperature is 800-1200° C. and the sintering time is 10-50 hours.

2. The preparation method according to claim 1, characterized in that The porosity of the isolation layer is 80-90%, and the average pore size of the through holes is 8-12 mm.

3. The preparation method according to claim 1 or 2, characterized in that The mechanical pressing is performed at a pressure of 50-220 MPa and for a time of 1-10 min.

4. The preparation method according to claim 3, characterized in that The mechanical pressing is performed at a pressure of 80-120 MPa and for a time of 3-5 minutes.

5. The preparation method according to claim 1, characterized in that The sintering temperature is 900-1100° C. and the sintering time is 20-30 hours.

6. The preparation method according to any one of claims 1 to 5, characterized in that The isolation layer is processed from high-temperature inert material into a circular plate with holes.

7. The preparation method according to claim 6, characterized in that The thickness of the isolation layer is 3-6 mm.

8. The preparation method according to any one of claims 1 to 7, characterized in that The mixing speed is 200-500 r / min and the mixing time is 5-10 h.

9. The preparation method according to any one of claims 1 to 8, characterized in that The blank is cylindrical, with a diameter of 15-70 mm and a height of 2-10 mm.

10. Iron-based superconducting tape powder prepared by the preparation method according to any one of claims 1 to 9.

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