MetaMateria Technologies, LLC — Department of Energy SBIR Phase II: 29a

Description

Even though there are encouraging reports on the suitability of Bi2212/Ag multi filamentary wires, the R&D efforts for high field magnets are focused on low temperature superconductors mostly due to availability in long continuous lengths with uniform properties. Improving the properties and the piece length of the Bi2212 superconductors is of highest importance. A reliable source of powder with definable properties is needed for the stabilization of the wire manufacturing process, particularly to avoid the JE limiting defects. Performance of a wire depends upon the interplay between powder characteristics, wire drawing process variables and configuration, and thermal processing of the wire. The proposed SBIR addresses the key challenges for demonstration scale (>1km lengths) wire for magnets with field between 25 T to 50T and focuses on improving JE, of round multi filamentary wires, reduce flaws in long length conductors and reduce cost by improving yield. During Phase I, a simple room temperature treatment was developed to produce flowable power with tap density 1.82 g/cc. The high density flowable powder is expected to facilitate wire manufacturability on large billet fabrication and enhance wire uniformity. No increase in particle size or carbon content was observed. The heat treatment conditions were optimized to reduce large secondary phases. These process improvements have led to a powder with minimal hard particles above 10 micron which is critical to produce long length multi filamentary wires with fine filaments (filament size <15 micron). During Phase II, the approaches will be refined and developed to eliminate any large hard particles that may have deleterious effect in long length wire. An air elutriation technique will be investigated to separate large (more than 10 μm) particles from the Bi2212 powder. The tap density of the powder will be selected based on the wire performance of Phase I powder. Round Bi2212/Ag multi filamentary wires will be fabricated at OST from one mid size billet (~2 kg) and two large billets (~ 10 kg) to demonstrate consistency of the powder process. Successful completion of the proposed program will enable availability of a reliable commercially viable domestic source of stable powder which is critical for downstream process stabilization of Bi2212/Ag composite wires for high field magnets. Key Words: High temperature super conductor, Bi2212 wires, JE, high field magnets.