Thermomechanical processing and reaction kinetics of Bi-2223 powder-in-tube tapes made from aerosol precursor

Abstract

Currently, powder-in-tube Bi-2223 superconductor is the most promising candidate for fabricating long-length conductors. Intensive investigations have shown that the critical current density of fully processed tapes is affected by a large variety of processing parameters. Among these are the thermomechanical processing schedule and the extent of Bi-2223 phase conversion. In this study, a powder precursor was prepared using an aerosol pyrolysis technique, which has been shown to have the advantage of reduced processing time. Powder-in-tube conductors were fabricated using the aerosol precursor powder, and the thermomechanical processing steps were varied. Different schedules were correlated with the amount of Bi-2223 phase as well as the critical current density. The number of pressings and the length of sintering time between pressings were found to be closely related to the critical current density at various stages of the thermomechanical treatment.

Phase development and critical current density of Bi-2223 tapes fabricated by groove rolling

“…The PIT technique presents a large number of variables some of which have considerable influence on the current transport properties of the tapes [12,18]. Among these are the phase assemblage of the precursor powder and its composition [12,19], initial tape deformation conditions [20,21], thermomechanical treatment conditions [22,23] and sample cooling rate [24].…”

Effects of stoichiometric variation and cooling rate on the phase formation and critical current density of Bi-2223 powder-in-tube tapes made from aerosol precursor

“…Based on the original composition (powder 1) used in a previous optimization study [13], two other aerosol precursor compositions with differing amount of Cu additions were prepared. The nominal compositions of the three powders are as follows: The first set of experiments (set A), which included three experimental sequences, was conducted to determine whether the optimum thermomechanical schedule found for powder 1 [13] will also result in the best performances for PIT tapes fabricated using powders 2 and 3. The first sequence (sequence 1) involved two short initial sintering intervals followed by a long one with intermediate pressings.…”

“…These treatments were performed on tapes made from powders 2 and 3, and the sequences listed in set B are based on a 25-25-50 treatment whereas those in set C are based on a 12-12-26-50 schedule. These two sets of sintering intervals were selected because they provided the best J c performances in tapes made from powder 1 with fast cooling in a previous study [13].…”

“…In a previous paper [13], we have reported on the effects of variation in thermomechanical sintering intervals on reaction kinetics as well as J c of PIT tapes containing aerosol precursor of Bi 1.84 Pb 0.34 Sr 1.91 Ca 2.03 Cu 3.07 O δ nominal composition, and showed that the PIT properties can be optimized using the proper sintering intervals. In the continuing development of the aerosol powder as a precursor for Bi-2223 PIT conductors, precursor powders of various Cu content were produced in this study.…”

Investigation of Bi-2223 high temperature superconducting tape as the material for gradient coil in MRI

“…The Bi-2223 tape is usually produced by the ''powder in tube'' (PIT) method [12]. It consists of arrays of (Bi 2Àx Pb x )Sr 2 Ca 2 Cu 3 O 10Ày , the effective superconducting material in the tape, embedded in a silver or alloy-silver matrix.…”