Method for preparing MgB2 superconducting material

Abstract

A preparation method of MgB2 superconducting material, weighing Mg powder and B powder according to the molar ratio Mg:B=1:2, and simultaneously weighing an organic acid whose mass is 5%-30% of the total mass of Mg powder and B powder Or organic acid salt, dissolve in 5-50mL acetone or ethanol, mix the obtained solution with Mg powder and B powder, ball mill for 1-10 hours, and then dry in a vacuum oven. Press the obtained powder into tablets to obtain MgB2 superconducting block material; or put the powder into a metal tube or a metal composite tube, and after sealing, perform swaging, drawing and rolling in sequence with a deformation rate of 5% to obtain a MgB2 superconducting wire strip material; put the obtained superconducting block or wire strip in a vacuum furnace, under the protection of vacuum or argon atmosphere, heat treatment temperature is 650°C-950°C, keep warm for 0.5-2 hours, and finally make MgB2 superconducting material. The MgB2 superconducting material prepared by the invention effectively overcomes the problems of oxidation and spontaneous combustion of the refined magnesium powder after high-energy ball milling, and at the same time significantly improves the superconducting performance of the MgB2 superconducting material due to the introduction of dopants.

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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