Large-sized cylinder of Bi-2223/Ni meshes composite bulk for current lead

Abstract

In order to improve the critical current density (Jc) and mechanical property of Bi-2223 sintered bulk, Ni wire meshes were added in the bulk. For fabricating large-sized cylindrical Bi-2223/Ni meshes composite, composing meshes are easy to produce compared with adding a lot of wires. The mesh concentration was 18×18 meshes/cm2 using Ni wires of 0.25mm in diameter. The Ni meshes were plated with Ag by 0.03mm in thickness. We prepared the cylindrical sintered bulk for a current lead, 32mm in outer diameter, 2mm in thickness and 110mm in length using a cold isostatic pressing (CIP) method. The samples were sintered at 845°C for 50h. After treatment again with CIP as an intermediate pressing, the samples were re-sintered. Small species were cut from the cylinder for measurement of critical current density (Jc) at 77K under self-field. There existed higher Jc portions and low Jc portions in the composite cylinder. Scanning electron microscope (SEM) observation showed that highly c-axis oriented and densely structured Bi-2223 plate-like grains could be formed around the interfacial region between the superconducting oxide and the Ag-plated Ni wires. There observed structural dislocation, which lead to low Jc portions in the cylinder.