Preparation method of carbon-doped magnesium diboride superconducting tape

Abstract

The invention relates to a preparation method of a carbon-doped magnesium diboride (MgB2) superconducting tape. The technical characteristic of the invention is characterized in that the method comprises the following steps that: a, a buffer layer film is deposed on a metal baseband; b, a malic acid-doped Mg(BH4)2 colloid is manufactured as well as the colloid is coated on the buffer layer film; c, the metal baseband that has been processed in the step b is placed under an protection atmosphere and is heated to a temperature of 300 to 500 DEG C, so that the malic acid- Mg(BH4)2 is deposed into a Mg(B1-XCX)2 superconductive alloy compound, wherein the X is equal to a value that is obtained by subtracting 0.l0 from 0.01; and d, metal having good electric conduction and heat conduction performances is covered on the surface of the Mg(B1-XCX)2 superconductive layer obtained by the step c so as to obtain a protection layer; that is, a practical carbon-doped MgB2 superconducting tape is obtained. Compared with a current method, the method provided in the invention enables the prepared MgB2 superconducting tape to have high critical current density, good heat stability and good flexibility; and moreover, manufacturing cost is low; and the method is suitable for industrialized production.

Description

technical field [0001] The invention relates to a method for manufacturing a superconducting strip, in particular to a method for preparing a carbon-doped magnesium diboride superconducting strip. Background technique [0002] High-performance superconducting materials are the basis for the development of large-scale superconducting power transmission, superconducting transformers, superconducting current limiters, superconducting magnets, superconducting energy storage and other applications. Magnesium diboride (MgB 2 ) superconducting tape is expected to replace traditional low-temperature superconducting materials and achieve large-scale commercial applications due to its high superconducting transition temperature, very high current carrying capacity, low raw material cost, and easy fabrication; especially in 15 Magnets with a temperature of ~26K and a magnetic field of less than 5T have huge market potential and are ideal for future medical nuclear magnetic resonance s...

AI Technical Summary

Problems solved by technology

[0005] 1) The critical current density is low and the superconductivity is poor; this method first mixes Mg powder and B powder, and then performs high temperature heat treatment

During the heat treatment, Mg diffuses to B, leaving holes in the Mg site, so that the generated MgB 2 The superconducting core is obviously porous and has a low density (usually only MgB 2 50% of theoretical density), resulting in MgB 2 The critical current density of the superconducting strip (J c ) is low and cannot meet the requirements of commercial applications

For example: usually at 20K, 3T, this strip J c Can only reach 500~600A / mm 2 ; Unable to satisfy MgB 2 Under the conditions of working temperature 20-26K and magnetic field 1.5-5T, the critical current density of superconducting strip is 1000A / mm 2 business application requirements

[0006] 2) Poor toughness, not easy to bend, and inconvenient to use: In order to improve the MgB in the superconducting core 2 The denseness of the coating layer used in the existing method is usually a high-strength metal or alloy in order to obtain a finer diameter wire, which is then rolled into a strip

The existence of the high-strength metal sheath cavity makes the overall toughness of the strip not enough, which brings difficulties in use and transportation

For example: for a superconducting strip with a thickness of 0.5mm and a width of 4mm produced by the existing method, the radius of curvature that does not damage the performance of the superconducting core is usually about 1 meter, and MgB is used to make magnets. 2 When making a superconducting tape, it usually needs to be wound on a cylindrical magnet with a radius not greater than 15cm. Therefore, it is difficult for the superconducting tape produced by the existing method to be used in commercial magnet applications.

[0007] 3) The production cost is high; firstly, in order to obtain a high critical current density, this MgB 2 Superconducting wire strips need to use high-purity amorphous boron powder, and this boron powder can only be produced in the United States at present, and the United States has restricted the export of this boron powder, so the production cost is very high

Second, the current MgB 2 The heat treatment temperature of the superconducting wire strip is usually 600-800°C, and the higher heat treatment temperature also increases the production cost