JP2004296156A - MANUFACTURING METHOD OF MgB2 SUPERCONDUCTING WIRE - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve critical current density, in a MgB<SB>2</SB>superconducting wire. <P>SOLUTION: This manufacturing method is used for manufacturing the MgB<SB>2</SB>superconducting wire by filling a metal tube with a mixture of Mg powder and B powder, by forming it into a tape-like or wire-like shape by cold-working it, and thereafter by heat-treating it. One or more kinds of compound powder selected from ZrSi<SB>2</SB>, ZrB<SB>2</SB>, WSi<SB>2</SB>, WB, WB<SB>2</SB>and MoB are added to the mixture of Mg powder and B powder. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The invention of this application relates to a method for manufacturing a MgB ₂ superconducting wire. More specifically, the invention of this application relates to a method for producing a MgB ₂ superconducting wire capable of improving the critical current density.
[0002]
[Prior art and its problems]
The MgB ₂ superconductor has a number of practical advantages such as being lightest and inexpensive in addition to exhibiting the highest critical temperature T _c = 39 K among metal-based superconductors. Due to such advantages, various studies have been made, such as use in a temperature range of about 20K where the cooling cost is suppressed, and a substitute for an Nb-Ti superconducting wire which is a practical material for a low magnetic field.
[0003]
As a method for producing the MgB ₂ superconducting wire, a so-called powder-in-tube method, which is a method in which a raw material powder is packed in a metal tube and processed and heat treated, is mainly used. However, this critical current density of the MgB ₂ superconducting wire is obtained to (J _c) does not reach a practical level, it is urgent improvement.
[0004]
Thus, for example, an attempt has been made to improve the critical current density of a MgB ₂ superconducting wire by adding SiC to a mixture of Mg powder and B powder (for example, see Non-Patent Document 1).
[0005]
The invention of this application has been made in view of the above circumstances, and has as an object to solve the problem of providing a method of manufacturing a MgB ₂ superconducting wire capable of improving the critical current density.
[0006]
[Non-patent document 1]
S. X. Dou et al., Enhancement of the critical current density and flux pinning of MgB ₂ superconductor by nanoparticulates, Sci., Ltd., 81st. 3419-3421
[0007]
[Means for Solving the Problems]
In order to solve the above problems, the invention of this application fills a metal tube with a mixture of Mg powder and B powder or a mixture of MgH ₂ powder and B powder, and forms a tape or wire by cold working. after, in the manufacturing method of the MgB ₂ superconducting wire to produce a MgB ₂ superconducting wire was heat-treated, ZrSi ₂ to a mixture of mixture or MgH ₂ powder and B powder Mg powder and B powder, _ZrB 2, WSi ₂ , WB, to provide a method of manufacturing a MgB ₂ superconducting wire, characterized by the addition of one or two or more compound powder is selected from the WB ₂ and MoB (claim 1).
[0008]
The invention of this application, the concentration of the compound powder when filling the metal tube, provided as one embodiment be 1-25 mol% with respect to MgB ₂ a (claim 2) produced by heat treatment.
[0009]
Hereinafter, the manufacturing method of the MgB ₂ superconducting wire of the present invention will be described in more detail with reference to examples.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
The manufacturing method of the MgB ₂ superconducting wire of the invention of this application follows the mainstream powder-in-tube method. That is, a method in which a mixture of Mg powder and B powder or a mixture of MgH ₂ powder and B powder is filled in a metal tube, formed into a tape or wire by cold working, and then heat-treated. In addition, in the method for manufacturing a MgB ₂ superconducting wire of the invention of the present application, the mixture of Mg powder and B powder contains one or two selected from ZrSi ₂ , ZrB ₂ , WSi ₂ , WB, WB ₂ and MoB. It was added compound powder above species, improving the critical current density of the MgB ₂ superconducting wire (J _c) by the addition of these compounds powders. The critical current density of the MgB ₂ superconducting wire to be manufactured _{(J c),} the above compound powder is 2 to 3.5 times the case of no addition.
[0011]
With respect to one or more compound powders selected from ZrSi ₂ , ZrB ₂ , WSi ₂ , WB, WB ₂ and MoB, the concentration at the time of filling the metal tube is set to 1 with respect to MgB ₂ generated by the heat treatment. Preferably, it is set to 〜25 mol%. If it is less than 1 mol%, the critical current density does not improve much, and if it exceeds 25 mol%, it affects the superconducting critical temperature (T _c ) of MgB ₂ and lowers T _c. Decrease.
[0012]
There is no particular limitation on the material of the metal tube, and iron, stainless steel, copper, copper-nickel alloy, and the like used in the powder-in-tube method can be appropriately selected.
[0013]
【Example】
A pure iron tube having an outer diameter of 6 mm and an inner diameter of 4 mm was mixed with Mg, B, and compound powders of ZrSi ₂ , WSi ₂ , and ZrB ₂ , filled, and processed into a tape shape in a cold state. ZrSi ₂ , WSi _2, and ZrB ₂ were added in an amount of 0 to 30 mol% based on MgB ₂ generated later. The particle size of the added powder of ZrSi ₂ , WSi ₂ and ZrB ₂ was ₂ to 7 μm. A short tape was cut out from the produced tape and heat-treated at 600 ° C. for 1 hour in an argon atmosphere. After the heat treatment, the iron sheath was removed, and the microstructure was examined by SEM and X-ray diffraction. Further, the superconducting transition temperature _{(T c)} measured by SQUID, the critical current density _{(J c)} - and the magnetic field (B) characteristic measured by resistance method.
[0014]
As a result of SEM observation, the particle size of MgB ₂ was 〜0.2 μm in both the sample to which no compound powder was added and the sample to which the compound powder was added. As a result of EDX analysis, W, Si, and Zr were detected in _two MgB grains in the tape to which the compound powder was added. T _c (onset) was 35.7K in the non-added sample, and decreased only by 0.5K in the added sample.
[0015]
FIG. 1 shows the dependence of the critical current density (J _c ) at 4.2 K on the external magnetic field (B) of an MgB ₂ tape prepared by adding 5 mol% of each compound powder of ZrSi ₂ , WSi ₂ and ZrB _2. it is a graph showing, in comparison with no addition MgB ₂ tapes.
[0016]
An external magnetic field was applied parallel to the tape plane.
[0017]
As confirmed from FIG. 1, J _c is improved by the addition of the compound powder, a large effect by the addition of ZrSi ₂ is in.
[0018]
Incidentally, in the _embodiment, when the addition amount of each compound powder of ZrSi _2, WSi _2, ZrB ₂ is less than 1 mol%, improvement of _{J c} is not expected so much, and when it exceeds 25 mol%, _{T c} decreases , _Jc also decreased.
[0019]
_Also, WB instead of _{ZrSi 2, WSi 2, ZrB 2} , was added to each compound powder of WB 2, MoB to prepare a MgB ₂ tapes _Similarly, ZrSi _2, WSi _2, of ZrB ₂ in the compound powder improved if similar to the J _c of addition was confirmed.
[0020]
Of course, the invention of this application is not limited by the above embodiments. It goes without saying that various aspects are possible for details such as the material and size of the metal tube and the conditions for cold working.
[0021]
【The invention's effect】
As described above in detail, the critical current density of the MgB ₂ superconducting wire is improved by the invention of this application. This is effective for putting the MgB ₂ superconducting wire into practical use.
[Brief description of the drawings]
FIG. 1 shows the dependence of the critical current density (J _c ) at 4.2 K on the external magnetic field (B) of an MgB ₂ tape prepared by adding 5 mol% of each compound powder of ZrSi ₂ , WSi ₂ and ZrB _2. it is a graph showing, in comparison with no addition MgB ₂ tapes.

Claims (2)

Mg powder and B powder mixture or MgH ₂ powder and B powder mixture of the filling in the metal tube, after the tape or wire form by cold working, MgB ₂ for producing a MgB ₂ superconducting wire was heat-treated In the method for producing a superconducting wire, one or two selected from ZrSi ₂ , ZrB ₂ , WSi ₂ , WB, WB ₂ and MoB are added to a mixture of Mg powder and B powder or a mixture of MgH ₂ powder and B powder. A method for producing a MgB ₂ superconducting wire, comprising adding the above compound powder. The concentration of the compound powder when filling the metal tube production method of the MgB ₂ superconducting wire according to claim 1 wherein 1 to 25 mol% with respect to MgB ₂ produced by thermal treatment.

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