Core Microstructure and Strain State Analysis in MgB2Wires with Different Metal Sheaths

C E Sobrero,M T Malachevsky,A Serquis

doi:10.1155/2015/297363

Abstract

We present a detailed analysis of the effect of the sheath materials on the microstructure and superconducting properties of MgB2wires produced by the powder-in-tube method (PIT). We reduced commercial MgB2powder by attrition milling in nitrogen atmosphere using tungsten carbide balls and obtained powders with grain sizes lower than 150 nm and different strain states through this process. Several Ti, stainless steel, and copper monofilamentary wires were prepared using these powders by the PIT method. We investigated different thermal treatments and mechanical paths during the processing of the wires for the enhancement of the critical currents. The superconducting properties were determined by magnetization measurements in a SQUID magnetometer. The correlation between the thermal treatments, structure, and superconducting properties is discussed.

Highlights

The superconducting critical temperature (Tc) of this binary compound makes MgB2 [1] attractive for cryogenic liquidfree technological applications
We present a detailed analysis of the effect of the sheath materials on the microstructure and superconducting properties of MgB2 wires produced by the powder-in-tube method (PIT)
In the present work we review the results obtained in MgB2 wires prepared by PIT using metal sheaths of different hardness: stainless steel, copper, or titanium, to establish a relationship among annealing conditions, modifications in the microstructure, and changes in Jc

Summary

Introduction

The superconducting critical temperature (Tc) of this binary compound makes MgB2 [1] attractive for cryogenic liquidfree technological applications. A remarkable progress has been done in increasing the critical current densities (Jc) by optimizing processing parameters. The powder-in-tube (PIT) method has been preferred early on by several groups to prepare MgB2 wires or tapes. Grain connectivity is more relevant for MgB2 wires and tapes required for applications, in which fabrication and processing conditions strongly affect microstructures and current carrying capability. The standard and low-cost fabrication PIT method involves filling a metallic tube with superconducting powder (ex situ) or precursors (in situ) and drawing it into a wire and/or rolling into a tape [6]. In the present work we review the results obtained in MgB2 wires prepared by PIT using metal sheaths of different hardness: stainless steel, copper, or titanium, to establish a relationship among annealing conditions, modifications in the microstructure, and changes in Jc

Experimental

Results and Discussion

Conclusions

Conflict of Interests