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Method for preparing MgB2 superconductive material by using spherical magnesium powder

A superconducting material, spherical technology, applied in the usage of superconducting elements, superconducting devices, superconducting/high-conducting conductors, etc., can solve the problem of poor grain connectivity, low critical current density of superconductors, and difficult to achieve grain size Nano-scale and other issues, to achieve the effect of improving the connectivity between grains and high critical current density

Inactive Publication Date: 2008-08-27
NORTHWEST INSTITUTE FOR NON-FERROUS METAL RESEARCH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Although the sintering process is simple, MgB is prepared from chip-shaped Mg powder. 2 The grain size is difficult to reach the nanometer level, and the connectivity between grains is poor (microstructure observation shows intergranular fracture), so the prepared MgB 2 Superconductors have low critical current densities under magnetic fields

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0015] Mix dry spherical magnesium powder and amorphous boron powder in a stoichiometric ratio of 1:2 in molar ratio, and perform high-energy ball milling under an argon protective atmosphere for 1 hour. The rotating speed of the tank is 800r / min, and the mixed powder of Mg and B after ball milling is added with 10% PVA (i.e. polyvinyl alcohol) and mixed thoroughly. The amount of PVA added is 3% of the weight of the mixed powder of Mg powder and B powder. The tube sintering furnace is vacuum-dried at a low temperature of 80°C, and then pressed into blocks; the pressed blocks are wrapped with Nb sheets and placed in a vacuum annealing furnace until the vacuum degree reaches 2.2×10 -3 After Pa, it is filled with argon protective atmosphere, heated at a heating rate of 20°C / min, kept at 750°C for 1 hour, and finally cooled at a cooling rate of 15°C / min to prepare MgB 2 Superconducting materials with a critical current density of 2×10 6 A / cm 2 (10K, 1T).

Embodiment 2

[0017] Mix dry spherical magnesium powder and amorphous boron powder in a stoichiometric ratio of 1:2 in molar ratio, and perform high-energy ball milling under an argon protective atmosphere for 1 hour. The rotating speed of the tank is 800r / min, and the mixed powder of Mg and B after ball milling is added with 5% PVA (i.e. polyvinyl alcohol) and mixed thoroughly. The amount of PVA added is 5% of the weight of the mixed powder of Mg powder and B powder. The tube sintering furnace is vacuum-dried at a low temperature of 80°C, and then pressed into blocks. Wrap the pressed blocks with Nb sheets and place them in a vacuum annealing furnace until the vacuum degree reaches 2.3×10 -3 After Pa, it is filled with argon protective atmosphere, heated at a heating rate of 20°C / min, kept at 750°C for 1 hour, and finally cooled at a cooling rate of 5°C / min to prepare MgB 2 Superconducting material with a critical current density of 1.8×10 6 A / cm 2 (10K, 1T).

Embodiment 3

[0019] Dry spherical magnesium powder and amorphous boron powder are mixed in a stoichiometric ratio of 1:2 in molar ratio, and high-energy ball milled for 2 hours under an argon protective atmosphere, the weight percentage of the ball material is 3:1, the ball milling jar is an agate jar, and the ball milling The rotation speed of the tank is 800r / min, the mixed powder of Mg and B after ball milling is added with paraffin and mixed thoroughly, the amount of paraffin added is 5% of the weight of the mixed powder of Mg powder and B powder, and the program-controlled single-tube sintering furnace is used for low-temperature vacuum drying at 100°C , and then pressed into blocks; wrap the pressed blocks with Ta sheets, place them in a vacuum annealing furnace, and wait until the vacuum degree reaches 2.5×10 -3 After Pa, it is filled with argon protective atmosphere, heated at a heating rate of 25°C / min, kept at 700°C for 2 hours, and finally cooled at a cooling rate of 15°C / min to ...

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PUM

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Abstract

The invention discloses a method for preparing MgB<2> superconductive material with high critical current density, via spherical powder. The preparation method comprises mixing dry spherical magnesium powder and amorphous boron powder at a suitable mol ratio, ball grinding under the protection of argon gas, adding the ball ground Mg-B mixed powder with organic adhesive to be mixed uniformly, drying at low temperature in vacuum, pressing into blocks or sheets, coating the pressed blocks or sheets via Nb or Ta sheets to be arranged in a vacuum annealing furnace, heating, insulating heat and cooling at vacuum under the protection of argon gas, to obtain MgB<2> superconductive material. The inventive preparation method has simple process, which can improve the crystal particle scale of MgB<2> to nanometer level and improve the intercrystalline connectivity of MgB<2>, to provide effective pinning center, therefore, the MgB<2> superconductor can realize high critical current density in magnetic field.

Description

technical field [0001] The invention belongs to the technical field of novel magnesium diboride superconducting materials, and in particular relates to the preparation of MgB with high critical current density by using spherical magnesium powder 2 approach to superconductors. Background technique [0002] MgB 2 It is a new type of superconducting material first discovered by Professor J.Akimitsu of Aoyama Gakuin University in 2001. Its crystal structure is AlB 2 type hexagonal structure. MgB 2 The critical current density J c It is jointly determined by intragranular pinning and intergranular connectivity. Therefore, on the one hand, it is necessary to increase the MgB 2 grain connectivity to improve the J c The magnetic field dependence; on the other hand, in order to improve the intragranular J c , an effective flux pinning center must be introduced, and both grain boundaries and non-superconducting second-phase equivalent crystal defects can be used as effective f...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C04B35/58C04B35/622H01B12/00
CPCY02E40/64Y02E40/60
Inventor 吴怡芳李成山闫果王庆阳刘国庆卢亚锋
Owner NORTHWEST INSTITUTE FOR NON-FERROUS METAL RESEARCH