Virtual-Impact Particle Sizing for Precursor Powders of Nb3Sn and Bi-2212 Superconductors

Particle size distribution is one of the critical parameters in fabricating high-performance, fine-filament superconductors of Nb3Sn and Bi-2212 using the powder-in-tube (PIT) technique. Even a few large particles in the tubes of a multi-filament PIT billet will limit the size of the drawing or rolling to finish dimension. Since performance scales with the number of filaments in a strand, improving the drawing limits should improve the ultimate performance of the superconducting strand. Virtual-impact processing (VIP), a technique originally developed to separate micron-size particles from air for environmental health studies, can be used to sort powders by particle size. By comparison to other techniques, VIP enables the removal of all particles with size greater than a desired threshold. This project will use a small-scale VIP to produce precursor powders of NbSn2, bronze, and sintered Bi-2212. The target particle size will be 2 mm; all particles of size > 4 mm will be removed. The various process parameters (geometry, air velocity, entrained powder density) as they will optimized and a design for scaling up the process to deliver ~kg/min quantities will be prepared.