Lawrence J. Masur

HTS wire at commercial performance levels

Short rolled multifilamentary BSCCO-2223 oxide-powder-in-tube (OPIT) wire has reached a core critical current density J/sub c/ over 73,000 A/cm/sup 2/ (77 K, self-field, 1 /spl mu/V/cm) in multiple samples, with engineering (full-cross-section) current density J/sub c/ of 22,800 A/cm/sup 2/ (77 K, self-field, 1 /spl mu/V/cm). Regular production wires several hundred meters long show average engineering current density over 10,000 A/cm/sup 2/ (77 K, self-field, 1 /spl mu/V/cm), a benchmark for commercial electric power applications such as cables and motors. Cost studies indicate that cost-performance below

Long length manufacturing of high performance BSCCO-2223 tape for the Detroit Edison Power Cable Project

10/kA-m is attainable for full-scale production levels, Next-generation YBCO-123 coated conductor technology offers further potential cost-performance improvements.

Multifilamentary Bi-2223 composite tapes made by a metallic precursor route

American Superconductor has manufactured the BSCCO-2223 tapes for the Detroit Edison Power Cable Project. Pirelli Cables and Systems, along with Detroit Edison, Lotepro, EPRI, and Los Alamos National Lab, are developing, manufacturing, and installing the worlds first HTS cable system in an electric utility network. Partially funded by the DOE-SPI program, the project goal is to fabricate, install, and test a 3-phase, 120-meter long, 100 MVA HTS cable system rated at 2400 A and 24 kV in Detroit Edisons Frisbie Station. Significant advances in HTS tape technology have been made in the past year, with average engineering critical current performance above 115 A at 77 K. We discuss the distribution of critical current as well as mechanical and environmental tests of more than 25 km of BSCCO tape manufactured for the Detroit Edison project. The environmental tests have been designed to simulate the behavior of HTS tapes under the actual operating conditions for an underground power cable.

Industrial high temperature superconductors: perspectives and milestones

A process based on metallic precursors has been developed for manufacturing high filament count oxide superconductor-silver composite tapes with critical current densities of up to 7.5 kA/cm/sup 2/ at 77 K in zero field. A 30-cm prototype multistrand conductor made of these tapes has a critical current of 240 A at 77 K over a 9 cm gauge length, with an average critical current density of 6 kA/cm/sup 2/. The mechanical properties of tapes made from metallic precursors containing up to 10000 Bi-2223 superconducting oxide filaments were investigated. Critical tensile strains average 0.6%, and bend tests show negligible dropoff in current density up to a 0.70% surface strain. The critical current decrease beyond the 0.70% surface bend strain follows a simple model based on extensive filament damage beyond the critical tensile strain. Increased flow stresses of the composite tapes, compared to similarly processed silver, indicate considerable strengthening of the composite by the oxide filaments.<<ETX>>

Advances in the development of silver sheathed (Bi,Pb)2223 composite conductors

High Temperature Superconductors (HTS) are widely considered for large power applications used by industrial end-users and electric utilities. The prominent application areas include power transmission cables, electric motors, generators, current limiters, and transformers. The promising design concepts rely on HTS to be a flexible composite conductor, robust enough to handle an industrial environment. Currently, the most advanced manufacturing method for flexible composite conductor is the Bi-2223-OPIT, used by many organizations. Significant advances in HTS technology have been made, with average critical current performance above 115 A at 77 K which is equivalent to an engineering current density of 13.8 kA/cm/sup 2/. During the past 18 months, American Superconductor increased its HTS wire manufacturing capacity from 250 km to 500 km per year to meet the increased demand for development and demonstrations. While this level of quality and quantity enables impressive demonstrations of prototype power applications, it does not fully meet the requirements of commercial economic viability. Therefore, to further decrease wire price to

Properties of high-Tc wires made by the metallic precursor process

50/kA-m, American Superconductor is currently siting a new facility dedicated to the manufacturing of Bi-OPIT-2223 wire in quantities of 10000 km per year. Initial applications for this wire are power transmission cables, industrial motors and electrical generators. This paper will report on the performance and reliability testing of Bi-2223 tapes. We will discuss the electrical, tensile, compression, and fatigue testing results of tapes manufactured for specific key projects. Also, we will review mass availability of High Temperature Superconductors and we will report on technological and price/performance limitations to be overcome to increase the applicability of HTS in research and industrial devices and equipment.

Dependence of critical current density on microstructure and processing of high-T c superconductors

Significant advances have been made in the critical current density of the technologically interesting (Bi,Pb)2223 composite conductors. Engineering current density, J/sub e/, of 9100 A/cm/sup 2/, corresponding to a filament current density, J/sub c/, of 32600 A/cm/sup 2/ (77 K, self-field) has been achieved by increasing the fraction of oxide in the conductor and improving the thermomechanical processing of the conductor. The filament microstructure may be further optimized by decreasing the volume fraction of secondary phases and porosity. The strain tolerance of the higher oxide fraction conductors remains adequate for applications by increasing the number of filaments in the conductors. Composite tapes with twisted filaments have been produced that have promising electrical properties in applied magnetic fields.<<ETX>>

Bi-axial texture in Ca0.1Y0.9Ba2Cu4O8 composite wires made by metallic precursors

The metallic precursor process, used in the production of high-temperature superconducting ceramics, exploits the relatively high formability of the metallic state to fabricate multifilament wires with excellent transport and mechanical properties. Multifilament wires, containing 9,583 filaments, exceed by tenfold the filament counts achieved by any other process. Oxide critical current densities of 17.7 kA/cm2 at 77 K in self-field surpass the best electrical performance reported for any other process used to fabricate multifilament composite wires. The mechanical properties of these wires approach the behavior of ideal composites, resulting in the flexibility, durability, and strain tolerance required for large-scale use in power generation, distribution, and end-use applications such as motors and current limiters.

Advances in the processing and properties of YBa2Cu4O8

Microstructural origins for reduced weak-link behavior in high-Jc melt-processed YBCO, spray pyrolyzed thick films of Tl-1223, metallic precursor Y-124 polycrystalline powder-in-tube (PIT) wires and PIT Bi-2212/2223 are discussed. Since the materials studied are the highest Jc, polycrystalline, high-Tc superconductors fabricated worldwide, the results provide important guidelines for further improvements in superconducting properties, thereby enabling practical applications of these materials. It is found that strongly linked current flow within domains of melt-processed 123 occurs effectively through a single crystal path. In c-axis oriented, polycrystalline Tl-1223 thick films, local in-plane texture has been found to play a crucial role in the reduced weak-link behavior. Formation of “colonies” of grains with a common c-axis and modest in-plane misorientation was observed. Furthermore, a colony boundary in general has a varying misorientation along the boundary. Large regions comprised primarily of low angle boundaries were observed. Percolative transport through a network of such small angle boundaries appears to provide the nonweak-linked current path. Although powder-in-tube BSCCO 2212 and 2223 also appear to have a “colony” microstructure, there are some important differences. Colonies in BSCCO consist of stacks of grains with similar c-axis orientation in contrast to colonies in Tl-1223 films where few grains are stacked on top of one another. Furthermore, most grains within a colony in BSCCO have the same lateral dimensions as that of the colony, resulting largely largely in “twist” boundaries. Further microstructural characterization of high-Jc PIT 2212 and 2223 is currently underway. In the case of Y-124 wires, weak macroscopic in-plane texture is found. Additional measurements are underway to determine if a sharper, local in-plane texture also exists. It is found that in three of the four types of superconductors studied, reduced weak-link behavior can be ascribed to some degree of biaxial alignment between grains, either on a “local” or a “global” scale.

Progress towards a long length metallic precursor process for multifilament Bi-2223 composite superconductors

Abstract High filament count, silver-sheathed composite wires of Ca 0.1 Y 0.9 Ba 2 Cu 4 O 8 (Y–124) were prepared by a metallic precursor route. The ductility of the metallic precursor enabled one to manufacture tapes containing up to 962 407 filaments, with filament dimensions as fine as 0.25 μm thick and 1 μm wide. By using a thermal-mechanical treatment to texture the Y–124 grains, transport critical current densities in the oxide filaments of 69 500 A/cm 2 at 4.2 K in self-field were obtained. Moreover, in an applied field of 0.1 T, the samples retained 39% of their self-field critical current density. A TEM investigation revealed significant bi-axial crystallographic texture: in areas viewed, c -axis alignment of adjacent grains was within 10° and oriented perpendicular to the tape face; a -axis alignment of adjacent grains was within 15° and oriented parallel to the longitudinal direction of the filaments. Furthermore, c -axis texture alone did not adequately predict the performance of these Y−124 composite conductors. Instead, performance scaled with the degree of bi-axial texture. These wires exhibited among the best reported J c for a polycrystalline, sintered wire of YBCO in an applied magnetic field.