Influence of Preparation Process on Microstructure, Critical Current Density and Tc of MgB2/Fe/Cu Wires

TL;DR

This study investigates how the preparation process affects the microstructure and superconducting properties of MgB2/Fe/Cu wires, showing that specific processing steps enhance grain connectivity and current density despite a lower Tc.

Contribution

It introduces a preparation method involving high energy milling and no intermediate annealing, leading to improved microstructure and flux pinning in MgB2 wires.

Findings

Small MgB2 grains (~20-100nm) observed after heat treatment.

Transport current density reaches 3×10^4 A/cm^2 at 15K and 3.5T.

No intermediate annealing used during rolling process.

Abstract

The powder-in-tube MgB2 wires were prepared by high energy milling of Mg and B powder. The powder was not mechanically alloyed for 2h short milling time. However, the MgB2 grains in wires are very small (20 100nm) and resembled to the dimple after post-heat treatment. The clear evidence for transcrystlline fracture is observed. It indicated that the grain connection was greatly improved and the fluxing pinning was significantly enhanced. Another point to view is no intermediate annealing was adopted during the whole rolling process. The influence of the post-heat treatment on the transport current density was studied. Despite the lower Tc of about 35K, the transport current density reaches to 3X10E4A/cm2 at 15K and 3.5T for 700 sintered wires.