Fabrication of high performance MgB2 wires by an internal Mg diffusion process

TL;DR

This paper reports the successful fabrication of high-performance MgB2 superconducting wires using an internal Mg diffusion process with SiC addition, resulting in significantly improved critical current density compared to traditional methods.

Contribution

The study introduces a novel internal Mg diffusion method with SiC addition for MgB2 wire fabrication, achieving higher density and Jc values than conventional powder-in-tube techniques.

Findings

MgB2 wires with high Jc values (>10^5 A/cm^2 at 8T) were fabricated.

Higher MgB2 layer density correlates with improved superconducting performance.

The process outperforms traditional PIT methods in critical current density.

Abstract

We succeeded in the fabrication of high-Jc MgB2/Fe wires applying the internal Mg diffusion (IMD) process with pure Mg core and SiC addition. A pure Mg rod with 2 mm diameter was placed at the center of a Fe tube, and the space between Mg and Fe tube was filled with B powder or the powder mixture of B-(5mol%)SiC. The composite was cold worked into 1.2mm diameter wire and finally heat treated at temperatures above the melting point of Mg(~650oC). During the heat treatment liquid Mg infiltrated into B layer and reacted with B to form MgB2. X-ray diffraction analysis indicated that the major phase in the reacted layer is MgB2. SEM analysis shows that the density of MgB2 layer is higher than that of usual powder-in-tube(PIT) processed wires. The wires with 5mol% SiC addition heat treated at 670oC showed Jc values higher than 105A/cm2 in 8T and 41,000A/cm2 in 10T at 4.2K. These values are much higher than those of usual PIT processed wires even compared to the ones with SiC addition. Higher density of MgB2 layer obtained by the diffusion reaction is the major cause of this excellent Jc values.