A method for preparing a bi-2212 precursor powder for significantly increasing the density of bi-2201 nanostreak phase in a bi-2212 wire

Abstract

The application discloses a preparation method of Bi-2212 precursor powder for significantly improving the Bi-2201 nanostripe phase density in Bi-2212 wires, and the Bi-2212 precursor powder is obtained by controlling the composition of a precursor solution, adjusting a fine heat treatment method, and controlling the molar ratio of Sr and Ca. The method of the application eliminates the large-size Bi-2201 phase by controlling the composition of the precursor solution and the heat treatment, controls the molar ratio of Sr and Ca in the powder within a proper range, and increases the nanostripe Bi-2201 phase density in the Bi-2212 wire, which is beneficial to improving the pinning performance of the Bi-2212 wire. The method is simple in operation, low in cost, strong in controllability and operability, and beneficial to improving the performance-price ratio of the Bi-2212 superconducting wire, and further promotes the rapid application of the Bi-2212 superconducting wire in the field of high-temperature superconducting magnets.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature superconducting material preparation technology, and in particular relates to a method for preparing Bi-2212 precursor powder that significantly improves the phase density of Bi-2201 nanostripes in Bi-2212 wire. Background Technology

[0002] While internationally reported methods such as high-voltage heat treatment of wires and the use of spray chemical combustion to prepare Bi-2212 powder have significantly improved the critical current density of Bi-2212 superconductors, the silver matrix used in Bi-2212 superconductors still keeps its cost high. Only by further increasing the critical current density of Bi-2212 superconductors can their cost-effectiveness be improved, ultimately strongly promoting their application in future large-scale high-field magnets.

[0003] The primary application of Bi-2212 wire is in low-temperature, high-field applications. As the field strength increases, the current-carrying capacity of the wire decreases, which is a normal and natural phenomenon. Currently, there are two main methods to improve the high-field current-carrying capacity of Bi-2212 wire: one is to improve the intrinsic current-carrying capacity of Bi-2212 wire under its own field, resulting in correspondingly higher current-carrying capacity at high fields; the other is to improve the pinning strength of Bi-2212 wire, reducing the rate at which its current-carrying capacity decays with the magnetic field. Existing research has theoretically and experimentally confirmed that the fine nano-Bi-2201 stripe phase in Bi-2212 wire is an effective pinning phase that can improve the pinning strength of the wire. However, the formation mechanism of the fine nano-Bi-2201 stripe phase in the wire is still unclear, and its density cannot be directionally controlled. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing Bi-2212 precursor powder with significantly improved Bi-2201 nano-stripe phase density in Bi-2212 wire. This preparation method involves setting the composition of the precursor liquid and precisely controlling the heat treatment process to first eliminate the Bi-2201 phase detectable by XRD, while simultaneously controlling the Sr to Ca molar ratio in the powder within a suitable range, thereby preparing Bi-2212 precursor powder with significantly improved Bi-2201 nano-stripe phase density in Bi-2212 wire.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is: a method for preparing Bi-2212 precursor powder with significantly improved Bi-2201 nano-stripe phase density in Bi-2212 wire, characterized in that the method controls the composition of the precursor liquid, adjusts it with a fine heat treatment method, and controls the molar ratio of Sr to Ca within a suitable range to obtain Bi-2212 precursor powder with significantly improved Bi-2201 nano-stripe phase density in Bi-2212 wire.

[0006] The above-mentioned method for preparing Bi-2212 precursor powder that significantly improves the phase density of Bi-2201 nanostripes in Bi-2212 wire is characterized by comprising the following steps: Step 1: Prepare Bi-2212 precursor solution according to the chemical formula of the target Bi-2212, and then prepare Bi-2212 raw powder based on the Bi-2212 precursor solution; Step 2: Heat-treat the Bi-2212 raw powder prepared in Step 1 to obtain Bi-2212 precursor powder that significantly improves the phase density of Bi-2201 nanostripes in Bi-2212 wire.

[0007] The method for preparing Bi-2212 precursor powder that significantly improves the phase density of Bi-2201 nanofibers in Bi-2212 wires, as described above, is characterized in that the chemical formula of the target Bi-2212 in step one is Bi. 2.12 Sr 1.94 Ca 0.89 Cu 2.0 O x , where x represents a non-fixed value.

[0008] The setting of the precursor liquid component in this invention is the key to ensuring that the subsequent powder components are within a specific range, and is a prerequisite for obtaining Bi-2212 precursor powder with significantly improved Bi-2201 nano-stripe phase density in Bi-2212 wire.

[0009] The above-mentioned method for preparing Bi-2212 precursor powder that significantly improves the phase density of Bi-2201 nanostripes in Bi-2212 wire is characterized in that the preparation method of Bi-2212 raw powder in step one is spray pyrolysis; the spray pyrolysis process is as follows: dissolving Bi2O3, SrCO3, CaCO3 and Cu in nitric acid to obtain a nitrate mixed solution, and preparing Bi-2212 raw powder using spray pyrolysis equipment.

[0010] This invention uses spray pyrolysis, a common method for preparing powders. The preparation technology is relatively mature, the equipment is relatively common, the operation is simple, and the cost is low, which greatly facilitates the preparation of Bi-2212 raw powder and makes it easier for the engineering application and promotion of the preparation method of this invention.

[0011] The preparation method of Bi-2212 precursor powder that significantly improves the phase density of Bi-2201 nano-stripes in Bi-2212 wire is characterized in that the heat treatment process in step two is as follows: Bi-2212 raw powder is kept at a temperature of 640℃~850℃ in sections and ground in an air environment, and then kept at 865℃±10℃ for 10h and ground to obtain powder. XRD analysis was used to analyze the second phase in the powder. When no Bi-2201 phase appeared in the powder, ICP analysis was performed. When the molar ratio of Sr to Ca in the powder was 2.33 and the coefficient of variation did not exceed 1%, and the relative error between the molar number of each element in the powder and the molar number of each element in the target Bi-2212 in step one was less than 7%, the heat treatment was completed, and Bi-2212 precursor powder with significantly improved Bi-2201 nano-stripe phase density in Bi-2212 wire was obtained.

[0012] Since the fine nano-Bi-2201 stripe phase in Bi-2212 wire is an effective pinning phase that can improve the pinning strength of Bi-2212 wire, but if the Bi-2201 phase can be detected by XRD in the powder, it indicates that there is too much Bi-2201 phase in the powder, and indirectly reflects that the size of the second phase is larger, the content of ineffective pinning phase is increased, and ultimately the pinning effect of the fine nano-Bi-2201 phase is weakened. This invention, by controlling the Bi-2212 precursor liquid to be a specific component and combining it with fine adjustments to the heat treatment process, removes the Bi-2201 phase detectable by XRD in the powder while ensuring that the molar ratio of Sr to Ca is within a suitable range. This results in the preparation of Bi-2212 precursor powder with a significantly increased density of Bi-2201 nano-stripe phase in Bi-2212 wires. The prepared Bi-2212 wires contain a higher density of fine striped nano-Bi-2201 pinning phase than conventional wires, which is beneficial to improving the pinning strength of Bi-2212 wires and maintaining the wires' current-carrying performance at low temperatures and high fields. This lays the foundation for the application of the wires in low-temperature, high-field magnets.

[0013] This invention, through precise adjustments to the heat treatment process and XRD data analysis, ensures that the final Bi-2212 precursor powder contains no large amounts of Bi-22O1 phase. Furthermore, ICP analysis confirms that the Sr to Ca molar ratio of the heat-treated powder remains within a suitable range. This guarantees a stable and significantly increased density of the Bi-22O1 nano-stripe phase in the final wire, ultimately improving the pinning performance of the Bi-2212 wire and ensuring excellent current-carrying capacity at low temperatures and high fields, thus promoting its engineering applications. The multi-step grinding heat treatment method effectively eliminates a large amount of intermediate Bi-22O1 phase during the Bi-2212 phase evolution process, ensuring the pinning effect of the subsequent nano-stripe Bi-22O1 phase.

[0014] The preparation method of Bi-2212 precursor powder that significantly improves the phase density of Bi-2201 nanostripes in Bi-2212 wire is characterized in that the segmented heat preservation temperatures are 640℃, 800℃, 820℃ and 850℃ respectively.

[0015] Compared with the prior art, the present invention has the following advantages: 1. This invention uses a specific Bi-2212 precursor liquid component to determine a fine heat treatment process for the powder, and combines a simple and rapid powder phase and component characterization method to determine for the first time a Bi-2212 precursor powder component and its preparation method that significantly improves the phase density of Bi-2201 nano-stripes in Bi-2212 wire, ultimately improving the pinning performance of Bi-2212 wire.

[0016] 2. The preparation method of the present invention is simple to operate, low in cost, highly controllable and operable, and has a high output-to-input ratio, which is conducive to its rapid application in Bi-2212 superconducting materials and further promotes the engineering application of Bi-2212 superconducting materials in high-field magnets.

[0017] 3. The Bi-2212 wire prepared in this invention significantly improves the Bi-2201 nano-stripe phase density in Bi-2212 wire, and the Bi-2201 nano-stripe phase density in this Bi-2212 wire is increased by more than 57% compared with conventional Bi-2212 wire.

[0018] 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

[0019] Figure 1 This is a TEM image of the Bi-2212 wire prepared in Example 1 of the present invention.

[0020] Figure 2 This is a TEM image of the Bi-2212 wire prepared in Comparative Example 1 of the present invention. Detailed Implementation

[0021] Example 1 The method in this embodiment includes the following steps: Step 1: Based on the chemical formula of the target Bi-2212, Bi 2.12 Sr 1.94 Ca 0.89 Cu 2.0 O x Bi2O3, SrCO3, CaCO3 and Cu were dissolved in nitric acid to obtain a nitrate mixed solution, and Bi-2212 raw powder was prepared by spray pyrolysis equipment; Step 2: Under air conditions, the Bi-2212 raw powder prepared in Step 1 was sequentially heated and ground at 640℃, 800℃, 820℃, and 850℃ in stages. Then, it was heated at 865℃±10℃ for 10 hours and ground again to obtain powder. XRD analysis was performed on the second phase in the powder, and no Bi-2201 phase was found. ICP analysis was then performed, and the molar ratio of Sr to Ca in the powder was 2.33, the coefficient of variation of the molar ratio of Sr to Ca was 0.91%, and the maximum relative error between the molar number of each element in the powder and the molar number of each element in the target Bi-2212 was 6.7%. The heat treatment was completed to obtain Bi-2212 precursor powder with significantly improved Bi-2201 nano-stripe phase density in Bi-2212 wire.

[0022] The Bi-2212 precursor powder, which significantly improved the Bi-2201 nanofiber phase density in the Bi-2212 wire obtained in this embodiment, was assembled into a tube and then subjected to a bundle drawing process to obtain the Bi-2212 wire. Microscopic analysis of the Bi-2212 wire was performed, such as... Figure 1 As shown, the Bi-2212 wire has 35 nano-Bi-2201 stripe phases.

[0023] Comparative Example 1 This comparative method includes the following steps: Step 1: Based on the target Bi-2212 chemical formula Bi 2.07 Sr 1.94 Ca 0.89 Cu 2.0 O x Bi2O3, SrCO3, CaCO3 and Cu were dissolved in nitric acid to obtain a nitrate mixed solution, and Bi-2212 raw powder was prepared by spray pyrolysis equipment; Step 2: Under air conditions, the Bi-2212 raw powder prepared in Step 1 was sequentially heated and ground at 640℃, 800℃, 820℃, and 850℃ in stages. Then, it was heated at 865℃±10℃ for 10 hours and ground again to obtain powder. XRD analysis was performed on the second phase in the powder, and no Bi-2201 phase was found. ICP analysis was then performed, and the molar ratio of Sr to Ca in the powder was 2.22, the coefficient of variation of the molar ratio of Sr to Ca was 1.3%, and the maximum relative error between the molar number of each element in the powder and the molar number of each element in the target Bi-2212 was 2.2%. The heat treatment was completed to obtain Bi-2212 precursor powder.

[0024] The Bi-2212 precursor powder obtained in this comparative example was assembled into a tube and then subjected to a bundle drawing process to obtain Bi-2212 wire. Microscopic analysis of the Bi-2212 wire was performed, such as... Figure 2 As shown, the Bi-2212 wire has 22 nano-Bi-2201 stripe phases. The nano-Bi-2201 stripe phase density of the Bi-2212 wire obtained in Example 1 is 1.59 times that of the Bi-2201 nano-stripe phase density in Comparative Example 1.

[0025] The current carrying capacity of the Bi-2212 wires obtained in Example 1 and Comparative Example 1 was tested at 4.2K self-field and 12T. The current carrying capacity of the Bi-2212 wire in Example 1 decreased by only 58%, while the current carrying capacity of the Bi-2212 wire in Comparative Example 1 decreased by 65%.

[0026] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Any simple modifications, alterations, or equivalent structural transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing Bi-2212 precursor powder to increase the phase density of Bi-2201 nanostripes in Bi-2212 wire, characterized in that, The method includes the following steps: Step 1: Prepare a Bi-2212 precursor solution according to the chemical formula of the target Bi-2212, and then prepare Bi-2212 raw powder based on the Bi-2212 precursor solution; the chemical formula of the target Bi-2212 is Bi. 2.12 Sr 1.94 Ca 0.89 Cu 2.0 O x x represents a non-fixed value; Step 2: Heat-treat the Bi-2212 raw powder prepared in Step 1 to obtain Bi-2212 precursor powder that improves the phase density of Bi-2201 nano-stripes in Bi-2212 wire. The heat treatment process is as follows: Bi-2212 raw powder is kept at 640℃~850℃ in stages and ground in an air environment, and then kept at 865℃±10℃ for 10 hours and ground to obtain powder. The temperature of the staged heat treatment is 640℃, 800℃, 820℃ and 850℃ respectively. XRD analysis was used to analyze the second phase in the powder. ICP analysis was performed when no Bi-2201 phase appeared in the powder. Heat treatment was completed when the molar ratio of Sr to Ca in the powder was 2.33 and the coefficient of variation did not exceed 1%, and the relative error between the molar number of each element in the powder and the molar number of each element in the target Bi-2212 in step one was less than 7%.

2. The method for preparing Bi-2212 precursor powder to improve the phase density of Bi-2201 nanostripes in Bi-2212 wire according to claim 1, characterized in that, The preparation method of Bi-2212 raw powder in step one is spray pyrolysis; the spray pyrolysis process is as follows: Bi2O3, SrCO3, CaCO3 and Cu are dissolved in nitric acid to obtain a nitrate mixed solution, and Bi-2212 raw powder is prepared by spray pyrolysis equipment.

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