Near-net-shape fabrication of continuous Ag-clad Bi-based superconductors
We have developed a near-net-shape process for Ag-clad Bi-2212 superconductors. This alternative to the powder-in-tube process offers the advantages of nearly continuous processing, minimization of processing steps, reasonable ability to control the Bi-2212/Ag ratio, and early development of favorable texture of the Bi-2212 grains. The powder is rolled into an Ag channel, a cap is applied, and the assembly is lightly rolled. To minimize distortion during heat treatment, it is especially important that the Bi-2212 powder be nearly free of volatile species such as carbon. A vacuum-calcination process was developed to control CO/sub 2/ evolution during heating. Superconducting properties are discussed.
Commercialization of ceramic superconductor composite wires
Recent advances in the development of high-temperature superconductor (HTS) composite wires demonstrate an increasingly realistic potential for commercial applications, such as power transmission cables, motors, and superconducting magnetic energy storage (SMES) systems. Successful commercialization requires the development of manufacturing technologies that can produce high-performance, low-cost HTS wires. The achievement of this goal has been occurring through an understanding of the basic relationships between the processing, properties, and microstructures of complex ceramic superconductors. Remarkable results have already been demonstrated with the oxide-powder-in-tube (OPIT) process. The purpose of this paper is to review the recent progress of OPIT-processed HTS composite wires and prototype products fabricated from these wires.
Improvement of Reproducibility of High Transport Jc for Bi2Sr2CaCu2Oy/Ag Tapes by Controlling Bi Content
A new method to obtain high Jc Bi-2212/Ag tapes with high reproducibility was developed. Melt-solidifying with Bi2Al4O9 is found to be an effective method for suppressing the vaporization of bismuth oxide during the high-temperature heat treatment. By application of this method, the homogeneity of the microstructure of the Bi-2212 layer was improved considerably due to a decrease of the Bi-poor phase, (Sr, Ca)-Cu-O. The reproducibility of Jc values was also improved corresponding to the microstructure, and Jc maintained more than 1×105 A/cm2 at 4.2 K in 7 T even for a 1 m tape.