Reactions Between Bi-2212 and Silver-Nickel Composite Sheath

The use of a Ag-Ni composite sheath has been proposed as a means to improve the mechanical performance and reduce the cost of Bi-2212 conductor. However, Bi-2212 is highly reactive with metals other than Ag and the precious metals. Previous work has also shown that the Cu-oxide in Bi-2212 will react with oxides applied to the exterior of the Ag sheath. To investigate the feasibility of using a Ni reinforced composite sheath, a monocore tape was fabricated using a Ag sheathing tube reinforced with 44 volume percent Ni filaments. The tape was melt processed in oxygen and argon atmospheres and the structure of the Ni filaments and oxide core was examined. The Ni filaments were found to completely oxidize and incorporate Cu from the core. The oxide in the core was depleted in Cu as a result, which affected 2212 phase formation.