A method for preparing doped magnesium diboride superconducting wire

Abstract

The invention discloses a method for preparing a doped magnesium diboride superconducting wire, comprising: drilling a plurality of holes on a nickel-based alloy ingot; adding an organic binder to boron powder and then mixing and extruding to obtain a boron tube; placing a magnesium-aluminum alloy rod in the boron tube to obtain a multi-core magnesium diboride composite ingot; obtaining a multi-core magnesium diboride wire by cold drawing; copper plating and heat treating the multi-core magnesium diboride wire to obtain a magnesium diboride superconducting wire. The invention adopts a nickel-based alloy as a metal matrix, so that the wire does not produce surface cracks during the entire processing process, and can be directly stretched to the final specification without introducing annealing. A carbon-based compound is used as an adhesive, and carbon atom doping is introduced during the phase formation process to effectively improve the irreversible field of the magnesium diboride superconducting wire and the critical current density under high field. A magnesium-aluminum alloy rod with a low aluminum content is used as a central magnesium source, which is conducive to improving the upper critical magnetic field of magnesium diboride.

Description

Technical Field

[0001] The invention relates to the technical field of superconducting wires, and in particular to a method for preparing a doped magnesium diboride superconducting wire. Background Art

[0002] At present, the production of practical magnesium diboride wire strip mainly adopts the powder tube method, that is, the magnesium diboride precursor powder is loaded into a metal sheath such as copper, niobium and monel alloy, and after a series of cold processing such as rolling and drawing, the magnesium diboride superconducting wire strip is obtained by phase heat treatment. Because it needs to undergo a continuous multi-pass cold processing process, the plasticity of the metal matrix is ​​required to be high. Pure niobium has become the first choice for the barrier layer due to its good processing plasticity and chemical stability. The magnesium diboride wires produced by the in-situ powder tube method reported so far almost all use metal niobium as a barrier layer, but the high price of niobium greatly increases the cost of magnesium diboride superconducting wires and limits their application. Metals such as iron and nickel have low costs, but they are prone to work hardening and cracking during processing, and need to be annealed multiple times at a higher temperature. The in-situ wire generally begins to pre-phase at 500°C. Annealing below this temperature cannot effectively improve the plasticity of iron and nickel, which becomes a bottleneck problem that restricts the preparation of long wires of iron and nickel barrier layer wires. In addition, the critical current density of magnesium diboride superconducting materials decays rapidly with the increase of magnetic field, which limits its application to a lower magnetic field range (1~4T). Summary of the invention

[0003] The embodiment of the present invention provides a method for preparing a doped magnesium diboride superconducting wire, which is used to solve the problems in the prior art that when metals such as iron and nickel are used as barrier layers, they are prone to hardening and cracking during processing, the wire is difficult to prepare long wires, the critical current density of the magnesium diboride superconducting material decays rapidly with the increase of the magnetic field, and the application field is limited to a relatively low magnetic field range.

[0004] On the one hand, an embodiment of the present invention provides a method for preparing a doped magnesium diboride superconducting wire, comprising:

[0005] Drilling a plurality of holes in a nickel-based alloy ingot;

[0006] Degreasing, cleaning and drying the holes;

[0007] Adding an organic binder to the boron powder and then mixing and extruding the mixture to obtain a boron tube having an outer diameter corresponding to the inner diameter of the hole;

[0008] Placing the boron tube into the hole to obtain a boron-nickel based alloy ingot;

[0009] Putting a magnesium-aluminum alloy rod having an outer diameter corresponding to the inner diameter of the boron tube into the boron tube of the boron-nickel-based alloy ingot to obtain a multi-core magnesium diboride composite ingot;

[0010] The multi-core magnesium diboride composite ingot is cold drawn to obtain a multi-core magnesium diboride wire;

[0011] copper plating and heat treating the multi-core magnesium diboride wire to obtain a magnesium diboride superconducting wire;

[0012] The nickel-based alloy ingot comprises nickel, magnesium, titanium, zirconium and copper.

[0013] In a possible implementation, the degreasing is performed by a metal degreasing agent, and the cleaning is performed by dilute nitric acid.

[0014] In a possible implementation manner, the organic binder is a carbon-based high molecular organic compound, and the elements of the organic binder include carbon, hydrogen and oxygen.

[0015] In a possible implementation, the copper plating electrolyte is a copper sulfate solution, the copper plating electrolytic cell anode is a crude copper plate, and the copper plating electrolytic cell cathode is the magnesium diboride superconducting wire.

[0016] In a possible implementation, the step of adding an organic binder to the boron powder and then mixing and extruding to obtain a boron tube having an outer diameter corresponding to the inner diameter of the hole comprises:

[0017] Mix the boron powder with the organic binder and wet it with alcohol:

[0018] The wetted mixture of the boron powder and the organic binder is loaded into the die hole of a molding machine for pressing to obtain a boron tube.

[0019] In a possible implementation manner, the hole is a single-sided opening.

[0020] In a possible implementation, placing a magnesium-aluminum alloy rod having an outer diameter corresponding to the inner diameter of the boron tube into the boron tube of the boron-nickel-based alloy ingot to obtain a multi-core magnesium diboride composite ingot includes:

[0021] Putting the magnesium-aluminum alloy rod into the boron tube;

[0022] The openings of the holes of the boron-nickel based alloy ingot are closed to obtain a multi-core magnesium diboride composite ingot.

[0023] The method for preparing a doped magnesium diboride superconducting wire in the present invention has the following advantages:

[0024] (1) A nickel-based alloy with high strength and good processing plasticity is used as the metal matrix. The powder is loaded into a porous alloy ingot by drilling and then cold-drawn to directly obtain a multi-core wire of the final specification. This avoids secondary assembly, reduces the total processing strain of drawing, and is beneficial to reducing the work hardening rate, so that the wire will not produce surface cracks during the entire processing process and can be directly stretched to the final specification without introducing annealing.

[0025] (2) Use nickel-based alloys with high nickel content. The elements titanium, zirconium, etc. contained in them can enter the magnesium diboride lattice as a benign doping source. The low price of nickel-based alloys is conducive to reducing the raw material cost of magnesium diboride superconducting wires.

[0026] (3) When carbon-based compounds are used as binders, the carbon atoms released by decomposition during the phase-forming heat treatment can replace the boron in the magnesium diboride lattice, causing the lattice constant a to decrease. This carbon doping can increase the carrier density and increase impurity scattering, effectively increasing the irreversible field of the magnesium diboride superconducting wire and the critical current density under high fields.

[0027] (4) A magnesium-aluminum alloy rod with a low aluminum content is used as the central magnesium source. Compared with conventional pure magnesium rods, magnesium alloy has better strength and processing plasticity. In addition, a small amount of aluminum can be used as a doping element to replace the magnesium atoms in the magnesium diboride lattice, causing the lattice constants a and c to decrease and produce lattice distortion, which is beneficial to increase the upper critical magnetic field of magnesium diboride. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 A schematic diagram of a method for preparing a doped magnesium diboride superconducting wire provided in an embodiment of the present invention;

[0030] Figure 2 A schematic diagram of drilling a nickel-based alloy ingot in a method for preparing a doped magnesium diboride superconducting wire provided in an embodiment of the present invention;

[0031] Figure 3 A schematic diagram of a single hole in a multi-core magnesium diboride composite ingot of a method for preparing a doped magnesium diboride superconducting wire provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Figure 1A schematic diagram of a method for preparing a doped magnesium diboride superconducting wire provided in an embodiment of the present invention; an embodiment of the present invention provides a method for preparing a doped magnesium diboride superconducting wire, comprising:

[0034] Drilling a plurality of holes in a nickel-based alloy ingot;

[0035] Degreasing, cleaning and drying the holes;

[0036] Adding an organic binder to the boron powder and then mixing and extruding the mixture to obtain a boron tube having an outer diameter corresponding to the inner diameter of the hole;

[0037] Placing the boron tube into the hole to obtain a boron-nickel based alloy ingot;

[0038] Putting a magnesium-aluminum alloy rod having an outer diameter corresponding to the inner diameter of the boron tube into the boron tube of the boron-nickel-based alloy ingot to obtain a multi-core magnesium diboride composite ingot;

[0039] The multi-core magnesium diboride composite ingot is cold drawn to obtain a multi-core magnesium diboride wire;

[0040] copper plating and heat treating the multi-core magnesium diboride wire to obtain a magnesium diboride superconducting wire;

[0041] The nickel-based alloy ingot comprises nickel, magnesium, titanium, zirconium and copper.

[0042] For example, Figure 2 , 3 As shown, multiple mounting holes of the same specification are drilled on a nickel-based alloy ingot, one end of the hole is closed, and the inner wall of the hole must be smooth and free of inclusions, and then the obtained porous nickel-based alloy ingot is degreased, cleaned, and dried for loading shed powder, and amorphous boron powder is welded with an organic adhesive to obtain a boron tube, the outer diameter of the boron tube corresponds to the inner diameter of the hole, and the outer diameter of the magnesium-aluminum alloy rod corresponds to the inner diameter of the boron tube. The magnesium-aluminum alloy rod is placed in the boron tube to obtain a multi-core magnesium diboride composite ingot, and the multi-core magnesium diboride composite ingot is cold-drawn to obtain a multi-core magnesium diboride wire, and then the multi-core magnesium diboride wire is copper-plated by electroplating, and the copper ratio of the wire is regulated by controlling the coating thickness, and then the copper-plated multi-core magnesium diboride wire is placed in a vacuum furnace and subjected to high-temperature phase heat treatment to obtain a magnesium diboride superconducting wire.

[0043] Among them, the nickel content in the nickel-based alloy ingot is greater than or equal to 70%, the magnesium, titanium and zirconium contents are less than or equal to 3% respectively, the copper content is less than or equal to 20%, and the trace element content is less than or equal to 1%.

[0044] The outer diameter of the nickel-based alloy ingot is 30-75 mm, the length is 500-1000 mm, the depth of the hole is 10-20 mm less than the length of the alloy ingot, and the number of the holes is 6-36.

[0045] In a possible embodiment, the degreasing is performed by a metal degreasing agent, and the cleaning is performed by dilute nitric acid; the organic binder is a carbon-based polymer organic compound, and the elements of the organic binder include carbon, hydrogen and oxygen; the copper-plated electrolyte is a copper sulfate solution, the copper-plated electrolytic cell anode is a crude copper plate, and the copper-plated electrolytic cell cathode is the magnesium diboride superconducting wire.

[0046] Exemplarily, the electrolyte used in the electroplating process is a copper sulfate solution, the anode of the electrolytic cell is a crude copper plate with a purity of 99%, the cathode is a magnesium diboride superconducting wire, and the coating thickness is controlled at 0.1-0.3 mm.

[0047] The degreasing is performed by using a metal degreasing agent, and the cleaning is performed by using dilute nitric acid with a volume ratio of 15-35%.

[0048] The boron powder is an amorphous boron powder with an average particle size of 200nm and a purity of 99.9%. The pressed boron tube has an outer diameter of 12-8mm. The adhesive used is a carbon-based macromolecular organic compound, which is composed of only three elements: carbon, hydrogen and oxygen, such as polyethylene glycol. It can be decomposed above 500°C to provide C atoms without generating other impurities that affect the phase formation. The amount of adhesive used does not exceed 5% of the weight of the boron powder.

[0049] The heat treatment is carried out in a high vacuum heat treatment furnace at a temperature of 600-750° C. for a time of 2-6 hours.

[0050] In a possible embodiment, the step of adding an organic binder to the boron powder and then mixing and extruding to obtain a boron tube having an outer diameter corresponding to the inner diameter of the hole comprises: mixing the boron powder and the organic binder and then wetting them with alcohol; and loading the wetted mixture of the boron powder and the organic binder into a die hole of a molding machine for pressing to obtain a boron tube. The hole is open on one side. The step of placing a magnesium-aluminum alloy rod having an outer diameter corresponding to the inner diameter of the boron tube into the boron tube of the boron-nickel-based alloy ingot to obtain a multi-core magnesium diboride composite ingot comprises: placing the magnesium-aluminum alloy rod into the boron tube; and sealing the opening of the hole of the boron-nickel-based alloy ingot to obtain a multi-core magnesium diboride composite ingot.

[0051] Exemplarily, the specifications of the magnesium-aluminum alloy rod are 5-10 mm in diameter and 500-1000 mm in length. In order to ensure that the critical transition temperature of magnesium diboride does not drop significantly after aluminum doping, the aluminum content in the magnesium-aluminum alloy rod must not exceed 3%, and the rest is magnesium; the specifications of the magnesium-aluminum alloy rod and the boron tube must be designed based on the premise that the molar ratio of magnesium:boron = 1.05:2.

[0052] In a possible embodiment, a plurality of circularly distributed mounting holes (non-through holes) with smooth inner walls of the same specifications are drilled on a nickel-based alloy ingot with an outer diameter of 45 mm and a length of 800 mm. The closed end of the hole is 20 mm from the bottom of the alloy ingot, i.e., the hole depth is 780 mm. The nickel content of the nickel-based alloy ingot is 73.6%, the magnesium content is 2.9%, the titanium content is 2.5%, the zirconium content is 1.8%, and the copper content is 18.3%. The total content of the remaining trace elements does not exceed 1%. The number of holes is 6, and the hole diameter is 11.1 mm. The surface is degreased with a metal cleaning agent, and then cleaned with a dilute nitric acid solution with a volume ratio of 20%. When the inner and outer walls of the hole are bright and free of pits and scratches, the hole is taken out and dried.

[0053] Take 54g of amorphous boron powder with an average particle size of 200nm and a purity of 99.9% and mix it thoroughly with 1.1g (accounting for 2.0% of the amount of boron powder) polyethylene glycol adhesive, then moisten it with alcohol, and put it into the mold hole of a molding machine to press it into a boron tube with an outer diameter of 11mm, a wall thickness of 2mm and a length of 780mm.

[0054] Insert the obtained boron tube into the mounting hole on the nickel-based alloy ingot obtained in step 1, close to the inner wall; insert a magnesium-aluminum alloy rod with an outer diameter of 7mm and a length of 780mm into the center of the boron tube. The aluminum content of the alloy rod is 2.0%, and the rest is magnesium; ensure that the boron tube and the magnesium-aluminum rod fit tightly, and perform the same operation on the other 5 mounting holes. After filling, close the ports to obtain a 6-core magnesium diboride composite ingot.

[0055] The obtained multi-core magnesium diboride composite ingot is cold processed by a wire drawing machine to a multi-core wire with a final specification of 0.8 mm in diameter, and the processing amount during the drawing process is 15%;

[0056] A metal copper plate with a purity of 99% and a length, width and thickness of 1000×500×20 mm is used as a soluble anode, and the magnesium diboride multi-core wire with a diameter of 0.8 mm obtained in step 4 is used as the cathode of the electrolytic cell, and a layer of copper with a thickness of 0.1 mm is uniformly plated on the surface of the magnesium diboride multi-core wire in a copper sulfate solution by controlling the current density and the electrolyte temperature;

[0057] The copper-plated MgB2 / Cu multi-core wire was wound onto a steel wire reel and placed in a vacuum heat treatment furnace at 600°C for 6 h. After high-temperature phase formation, a multi-core MgB2 superconducting wire was finally obtained. The wire of this specification was sampled for current carrying performance test, and its critical current density Jc=1.256×10 4 A / mm 2 .

[0058] In a possible embodiment, a plurality of mounting holes (non-through holes) with smooth inner walls of the same specifications are drilled on a nickel-based alloy ingot with an outer diameter of 45 mm and a length of 800 mm. The closed end of the hole is 20 mm from the bottom of the alloy ingot, i.e., the hole depth is 780 mm. The nickel content of the nickel-based alloy ingot is 78.4%, the magnesium content is 1.9%, the titanium content is 1.6%, the zirconium content is 1.2%, and the copper content is 16.3%. The total content of the remaining trace elements does not exceed 1%. There are 6 holes with a hole diameter of 11.1 mm. The surface is degreased with a metal cleaning agent, and then cleaned with a dilute nitric acid solution with a volume ratio of 20%. When the inner and outer walls of the hole are bright and free of pits and scratches, the hole is taken out and dried.

[0059] Take 54g of amorphous boron powder with an average particle size of 200nm and a purity of 99.9% and mix it thoroughly with 1.1g (accounting for 2.0% of the amount of boron powder) polyethylene glycol adhesive, then moisten it with alcohol, and put it into the mold hole of a molding machine to press it into a boron tube with an outer diameter of 11mm, a wall thickness of 2mm and a length of 780mm.

[0060] Insert the obtained boron tube into the mounting hole on the nickel-based alloy ingot obtained above, close to the inner wall; insert a magnesium-aluminum alloy rod with an outer diameter of 7mm and a length of 780mm into the center of the boron tube. The aluminum content of the alloy rod is 2.0%, and the rest is magnesium; ensure that the boron tube and the magnesium-aluminum rod fit tightly, and perform the same operation on the other 5 mounting holes. After filling, close the ports to obtain a 6-core magnesium diboride composite ingot.

[0061] The obtained multi-core magnesium diboride composite ingot is cold processed by a wire drawing machine to a multi-core wire with a final specification of 0.8 mm in diameter, and the processing amount during the drawing process is 15%;

[0062] A metal copper plate with a purity of 99% and a length, width and thickness of 1000×500×20 mm is used as a soluble anode, and the magnesium diboride multi-core wire with a diameter of 0.8 mm obtained in step 4 is used as the cathode of the electrolytic cell, and a layer of copper with a thickness of 0.1 mm is uniformly plated on the surface of the magnesium diboride multi-core wire in a copper sulfate solution by controlling the current density and the electrolyte temperature;

[0063] The copper-plated MgB2 / Cu multi-core wire was wound onto a steel wire reel and placed in a vacuum heat treatment furnace at 600°C for 6 h. After high-temperature phase formation, a multi-core MgB2 superconducting wire was finally obtained. The wire of this specification was sampled for current carrying performance test, and its critical current density Jc=1.281×10 4 A / mm 2 .

[0064] In a possible embodiment, a plurality of circularly distributed mounting holes (non-through holes) with smooth inner walls of the same specifications are drilled on a nickel-based alloy ingot with an outer diameter of 45 mm and a length of 800 mm. The closed end of the hole is 20 mm from the bottom of the alloy ingot, i.e., the hole depth is 780 mm. The nickel content of the nickel-based alloy ingot is 73.6%, the magnesium content is 2.9%, the titanium content is 2.5%, the zirconium content is 1.8%, and the copper content is 18.3%. The total content of the remaining trace elements does not exceed 1%. The number of holes is 6, and the hole diameter is 11.1 mm. The surface is degreased with a metal cleaning agent, and then cleaned with a dilute nitric acid solution with a volume ratio of 20%. When the inner and outer walls of the hole are bright and free of pits and scratches, the hole is taken out and dried.

[0065] Take 54g of amorphous boron powder with an average particle size of 200nm and a purity of 99.9% and mix it thoroughly with 3.0g (5.0% of the amount of boron powder) polyethylene glycol adhesive, then moisten it with alcohol, and put it into the mold hole of a molding machine to press it into a boron tube with an outer diameter of 11mm, a wall thickness of 2mm and a length of 780mm.

[0066] Insert the obtained boron tube into the mounting hole on the nickel-based alloy ingot obtained above, close to the inner wall; insert a magnesium-aluminum alloy rod with an outer diameter of 7mm and a length of 780mm into the center of the boron tube. The aluminum content of the alloy rod is 2.0%, and the rest is magnesium; ensure that the boron tube and the magnesium-aluminum rod fit tightly, and perform the same operation on the other 5 mounting holes. After filling, close the ports to obtain a 6-core magnesium diboride composite ingot.

[0067] The obtained multi-core magnesium diboride composite ingot is cold processed by a wire drawing machine to a multi-core wire with a final specification of 0.8 mm in diameter, and the processing amount during the drawing process is 15%;

[0068] A metal copper plate with a purity of 99% and a length, width and thickness of 1000×500×20 mm is used as a soluble anode, and the magnesium diboride multi-core wire with a diameter of 0.8 mm obtained in step 4 is used as the cathode of the electrolytic cell, and a layer of copper with a thickness of 0.1 mm is uniformly plated on the surface of the magnesium diboride multi-core wire in a copper sulfate solution by controlling the current density and the electrolyte temperature;

[0069] The copper-plated MgB2 / Cu multi-core wire was wound onto a steel wire reel and placed in a vacuum heat treatment furnace at 600°C for 6 h. After high-temperature phase formation, a multi-core MgB2 superconducting wire was finally obtained. The wire of this specification was sampled for current carrying performance test, and its critical current density Jc=1.374×10 4 A / mm 2 .

[0070] In a possible embodiment, a plurality of circularly distributed mounting holes (non-through holes) with smooth inner walls of the same specifications are drilled on a nickel-based alloy ingot with an outer diameter of 45 mm and a length of 800 mm. The closed end of the hole is 20 mm from the bottom of the alloy ingot, i.e., the hole depth is 780 mm. The nickel content of the nickel-based alloy ingot is 73.6%, the magnesium content is 2.9%, the titanium content is 2.5%, the zirconium content is 1.8%, and the copper content is 18.3%. The total content of the remaining trace elements does not exceed 1%. The number of holes is 6, and the hole diameter is 11.1 mm. The surface is degreased with a metal cleaning agent, and then cleaned with a dilute nitric acid solution with a volume ratio of 20%. When the inner and outer walls of the hole are bright and free of pits and scratches, the hole is taken out and dried.

[0071] Take 54g of amorphous boron powder with an average particle size of 200nm and a purity of 99.9% and mix it thoroughly with 3.0g (5.0% of the amount of boron powder) polyethylene glycol adhesive, then moisten it with alcohol, and put it into the mold hole of a molding machine to press it into a boron tube with an outer diameter of 11mm, a wall thickness of 2mm and a length of 780mm.

[0072] Insert the obtained boron tube into the mounting hole on the nickel-based alloy ingot obtained above, close to the inner wall; insert a magnesium-aluminum alloy rod with an outer diameter of 7mm and a length of 780mm into the center of the boron tube. The aluminum content of the alloy rod is 3.0%, and the rest is magnesium; ensure that the boron tube and the magnesium-aluminum rod fit tightly, and perform the same operation on the other 5 mounting holes. After the filling is completed, close the port to obtain a 6-core magnesium diboride composite ingot.

[0073] The obtained multi-core magnesium diboride composite ingot is cold processed by a wire drawing machine to a multi-core wire with a final specification of 0.8 mm in diameter, and the processing amount during the drawing process is 15%;

[0074] A metal copper plate with a purity of 99% and a length, width and thickness of 1000×500×20 mm is used as a soluble anode, and the magnesium diboride multi-core wire with a diameter of 0.8 mm obtained in step 4 is used as the cathode of the electrolytic cell, and a layer of copper with a thickness of 0.1 mm is uniformly plated on the surface of the magnesium diboride multi-core wire in a copper sulfate solution by controlling the current density and the electrolyte temperature;

[0075] The copper-plated magnesium diboride multi-core wire was wound onto a steel wire reel and placed in a vacuum heat treatment furnace at 600°C for 6 hours. After high-temperature phase formation, a multi-core magnesium diboride superconducting wire was finally obtained. The wire of this specification was sampled for current carrying performance test, and its critical current density Jc=1.301×10 4 A / mm 2 .

[0076] In a possible embodiment, a plurality of circularly distributed mounting holes (non-through holes) with smooth inner walls of the same specifications are drilled on a nickel-based alloy ingot with an outer diameter of 30 mm and a length of 500 mm. The closed end of the hole is 10 mm from the bottom of the alloy ingot, i.e., the hole depth is 490 mm. The nickel content of the nickel-based alloy ingot is 77.5%, the magnesium content is 0.5%, the titanium content is 0.5%, the zirconium content is 0.5%, the copper content is 20.0%, and the sum of the contents of other trace elements does not exceed 1%. The number of holes is 6, and the hole diameter is 8.1 mm. The surface is degreased with a metal cleaning agent, and then cleaned with a dilute nitric acid solution with a volume ratio of 15%. When the inner and outer walls of the hole are bright and free of pits and scratches, the hole is taken out and dried.

[0077] Take 18g of amorphous boron powder with an average particle size of 200nm and a purity of 99.9% and mix it thoroughly with 1.0g (5.0% of the amount of boron powder) polyethylene glycol adhesive, then moisten it with alcohol, and put it into the mold hole of a molding machine to press it into a boron tube with an outer diameter of 8mm, a wall thickness of 1.5mm and a length of 490mm.

[0078] Insert the obtained boron tube into the mounting hole on the nickel-based alloy ingot obtained above, close to the inner wall; insert a magnesium-aluminum alloy rod with an outer diameter of 5mm and a length of 490mm into the center of the boron tube. The aluminum content of the alloy rod is 3.0%, and the rest is magnesium; ensure that the boron tube and the magnesium-aluminum rod fit tightly, and perform the same operation on the other 5 mounting holes. After the filling is completed, close the port to obtain a 6-core magnesium diboride composite ingot.

[0079] The obtained multi-core magnesium diboride composite ingot is cold processed by a wire drawing machine to a multi-core wire with a final specification of 0.8 mm in diameter, and the processing amount during the drawing process is 15%;

[0080] A metal copper plate with a purity of 99% and a length, width and thickness of 1000×500×20 mm is used as a soluble anode, and the magnesium diboride multi-core wire with a diameter of 0.8 mm obtained in step 4 is used as the cathode of the electrolytic cell, and a layer of copper with a thickness of 0.1 mm is uniformly plated on the surface of the magnesium diboride multi-core wire in a copper sulfate solution by controlling the current density and the electrolyte temperature;

[0081] The copper-plated MgB2 / Cu multi-core wire was wound onto a steel wire reel and placed in a vacuum heat treatment furnace at 600°C for 2 h. After high-temperature phase formation, a multi-core MgB2 superconducting wire was finally obtained. The wire of this specification was sampled for current carrying performance test, and its critical current density Jc=1.401×10 4 A / mm 2 .

[0082] In a possible embodiment, a plurality of circularly distributed mounting holes (non-through holes) with smooth inner walls of the same specifications are drilled on a nickel-based alloy ingot with an outer diameter of 75 mm and a length of 1000 mm. The closed end of the hole is 20 mm from the bottom of the alloy ingot, i.e., the hole depth is 980 mm. The nickel content of the nickel-based alloy ingot is 70%, the magnesium content is 3.0%, the titanium content is 3.0%, the zirconium content is 3.0%, and the copper content is 20.0%. The total content of the remaining trace elements does not exceed 1%. The number of holes is 36, and the hole diameter is 8.1 mm. The surface is degreased with a metal cleaning agent, and then cleaned with a dilute nitric acid solution with a volume ratio of 35%. When the inner and outer walls of the hole are bright and free of pits and scratches, the hole is taken out and dried.

[0083] Take 36g of amorphous boron powder with an average particle size of 200nm and a purity of 99.9% and mix it thoroughly with 3.0g (accounting for 5.0% of the amount of boron powder) polyethylene glycol adhesive, then moisten it with alcohol, and put it into the mold hole of a molding machine to press it into a boron tube with an outer diameter of 8mm, a wall thickness of 1.5mm and a length of 980mm.

[0084] Insert the obtained boron tube into the mounting hole on the nickel-based alloy ingot obtained above, close to the inner wall; insert a magnesium-aluminum alloy rod with an outer diameter of 5mm and a length of 980mm into the center of the boron tube. The aluminum content of the alloy rod is 3.0%, and the rest is magnesium; ensure that the boron tube and the magnesium-aluminum rod fit tightly, and perform the same operation on the other 35 mounting holes. After the filling is completed, close the port to obtain a 36-core magnesium diboride composite ingot.

[0085] The obtained multi-core magnesium diboride composite ingot is cold processed by a wire drawing machine to a multi-core wire with a final specification of 0.8 mm in diameter, and the processing amount during the drawing process is 15%;

[0086] A metal copper plate with a purity of 99% and a length, width and thickness of 1000×500×20 mm is used as a soluble anode, and the magnesium diboride multi-core wire with a diameter of 0.8 mm obtained in step 4 is used as the cathode of the electrolytic cell, and a layer of copper with a thickness of 0.3 mm is evenly plated on the surface of the magnesium diboride multi-core wire in a copper sulfate solution by controlling the current density and the electrolyte temperature;

[0087] The copper-plated MgB2 / Cu multi-core wire was wound onto a steel wire reel and placed in a vacuum heat treatment furnace at 750°C for 6 h. After high-temperature phase formation, a multi-core MgB2 superconducting wire was finally obtained. The wire of this specification was sampled for current carrying performance test, and its critical current density Jc=1.104×10 4 A / mm 2 .

[0088] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0089] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for preparing a doped magnesium diboride superconducting wire, characterized in that: include: Drilling a plurality of holes in a nickel-based alloy ingot; Degreasing, cleaning and drying the holes; Adding an organic binder to the boron powder and then mixing and extruding the mixture to obtain a boron tube having an outer diameter corresponding to the inner diameter of the hole; Placing the boron tube into the hole to obtain a boron-nickel based alloy ingot; Putting a magnesium-aluminum alloy rod having an outer diameter corresponding to the inner diameter of the boron tube into the boron tube of the boron-nickel-based alloy ingot to obtain a multi-core magnesium diboride composite ingot; The multi-core magnesium diboride composite ingot is cold-drawn to obtain a multi-core magnesium diboride wire; copper plating and heat treating the multi-core magnesium diboride wire to obtain a magnesium diboride superconducting wire; The nickel-based alloy ingot comprises nickel, magnesium, titanium, zirconium and copper.

2. The method for preparing a doped magnesium diboride superconducting wire according to claim 1, characterized in that: The degreasing is performed by a metal degreasing agent, and the cleaning is performed by dilute nitric acid.

3. The method for preparing a doped magnesium diboride superconducting wire according to claim 1, characterized in that: The organic binder is a carbon-based high molecular organic compound, and the elements of the organic binder include carbon, hydrogen and oxygen.

4. The method for preparing a doped magnesium diboride superconducting wire according to claim 1, characterized in that: The copper plating electrolyte is a copper sulfate solution, the copper plating electrolytic cell anode is a crude copper plate, and the copper plating electrolytic cell cathode is the magnesium diboride superconducting wire.

5. The method for preparing a doped magnesium diboride superconducting wire according to claim 3, characterized in that: The step of adding an organic binder to the boron powder and then mixing and extruding to obtain a boron tube having an outer diameter corresponding to the inner diameter of the hole comprises: Mix the boron powder with the organic binder and wet it with alcohol: The wetted mixture of the boron powder and the organic binder is loaded into the die hole of a molding machine for pressing to obtain a boron tube.

6. The method for preparing a doped magnesium diboride superconducting wire according to claim 1, characterized in that: The hole is a single-sided opening.

7. The method for preparing a doped magnesium diboride superconducting wire according to claim 1, characterized in that: The step of placing a magnesium-aluminum alloy rod having an outer diameter corresponding to the inner diameter of the boron tube into the boron tube of the boron-nickel-based alloy ingot to obtain a multi-core magnesium diboride composite ingot comprises: Putting the magnesium-aluminum alloy rod into the boron tube; The openings of the holes of the boron-nickel based alloy ingot are closed to obtain a multi-core magnesium diboride composite ingot.

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