Method for preparing MgB2 superconducting material

Abstract

The invention relates to a process for preparing MgB2 superconductive material, wherein according to mol ratio Mg:B=1:2, the invention weights Mg powder and B powder, and weights organic acid or organic acid salt at 5-30% weight of total Mg powder and B powder, to be dissolved in 5-50mL acetone or alcohol, mixes the solution with Mg powder and B powder, to be ball milled for 1-10h, to be dried ina vacuum drying box, tablets the powder, to obtain MgB2 superconductive block, or fills the powder into metal tube or metal composite tube, to be sealed and rotationally forged, drawn or rolled with 5% deformation ratio, to obtain MgB2 superconductive band, arranges the superconductive block or band into a vacuum furnace, under vacuum to argon gas protection and thermal treatment temperature as 650-950DEG C, to keep temperature for 0.5-2h, to obtain MgB2 superconductive material. The inventive MgB2 superconductive material can effectively overcome the oxidation and self-combustion problems ofhigh-energy ball milled refined magnesium powder, and the invention adds doping material to significantly improve the superconductivity of the MgB2 superconductive material.

Description

technical field [0001] The present invention relates to a kind of MgB 2 Methods for the preparation of superconducting materials. Background technique [0002] Since the discovery of a new type of superconductor magnesium diboride (MgB) with a superconducting transition temperature as high as 39K in 2001, 2 ) Since then, scientists from various countries have conducted a large number of in-depth studies. At present, in the preparation of high-performance MgB 2 Among the wire and strip methods, the in-situ (in-situ) powder tube (Powder-In-Tube) technology is the most convenient and practical one, but its critical current density (Jc) is still low. Studies have shown that the particle size of the original powder has an effect on the MgB 2 The critical current density of superconducting materials plays an important role. The sample prepared by the Japanese research group using submicron or nanoscale magnesium powder can reach a higher critical current density ([Yamada H.Hi...

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Problems solved by technology

However, it is worth noting that the particle size of magnesium powder can be reduced to submicron level after high-energy ball milling. During the ball milling process, the oxide layer on the surface is easily peeled off, resulting in a sharp increase in specific surface area and a sharp increase in activity. Once in contact with oxygen or water vapor in the air, it is easy to oxidize or even spontaneously ignite; at the same time, fine boron powder is also very easy to absorb oxygen and be oxidized, which will undoubtedly seriously affect the performance of superconducting materials, and also bring new problems to the preparation process. considerable risk

In order to prevent the oxidation of magnesium powder after ball milling, some research groups are preparing MgB 2 When superconducting materials, the original powder is always kept under the protection of argon atmosphere ([W.Haessler et al, Superconducting MgB2 Tapes Prepared Using Mechanically Alloyed Nanocrystalline PrecursorPowder, Trans.Appl.Supercond.17(2007)2919]), but this obviously increases The complexity and difficulty of the actual operation lead to a sharp increase in the preparation cost, and at the same time, due to the limited argon protection space, the preparation efficiency of superconducting materials is low

In addition, some research groups use organic solvents such as acetone or ethanol to carry out wet ball milling on the original powder to prevent oxidation, but acetone or ethanol is extremely volatile, and once volatilized, the original powder will be completely exposed to the air again, so there is no Very effective in preventing oxidation

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