High-energy ball milling and synthesi temperature study to improve superconducting properties of MgB2 ex-situ tapes and wires

TL;DR

This study explores how high-energy ball milling and synthesis temperature influence the superconducting properties of MgB2 tapes and wires, optimizing critical current density through specific processing parameters.

Contribution

It introduces a systematic investigation of milling time, speed, and synthesis temperature to enhance MgB2 superconducting performance in ex-situ tapes and wires.

Findings

Maximum Jc of 6 x 10^4 A/cm^2 at 5 K and 4 T achieved

Optimal synthesis temperature identified at 745°C for best Jc

Proposed fluidifying effect of unreacted magnesium improves grain connectivity

Abstract

MgB2 monofilamentary nickel-sheated tapes and wires were fabricated by means of the ex-situ powder-in-tube method using either high-energy ball milled and low temperature synthesized powders. All sample were sintered at 920 C in Ar flow. The milling time and the revolution speed were tuned in order to maximize the critical current density in field (Jc): the maximum Jc value of 6 x 10e4 A/cm2 at 5 K and 4 T was obtained corresponding to the tape prepared with powders milled for 144h at 180rpm. Vorious synthesis temperature were also investigated (730-900 C) finding a best Jc value for the wire prepared with powders synthesized at 745 C. We speculate that this optimal temperature is due to the fluidifying effect of unreacted magnesium content before the sintering process which could better connect the grains.