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

65438 Large particles must be efficiently removed from powders used to fabricate superconducting wire. The presence of even a trace amount of large particles can ruin the superconducting properties of a large batch of wire, and limit the performance of all wire made with the powder-in-tube process. This project will apply an aerosol sorting technology to remove this limitation to superconductor cost and performance. The approach adapts a technique called virtual impact sizing, in which the powder is dispersed in an air stream and passed through a sequence of nozzles. The nozzles are arranged so that the heavy particles must pass into one exit duct while the light particles pass into another duct, with a very sharp cutoff between the sizes that go the two ways. Phase I demonstrated 99.7% rejection of large particles from the small particle exit stream. An optimal design was demonstrated to process 1kg/hour from each nozzle array at a cost of ~$30/kg, a significant result since high-performance superconducting wire costs $1,000-$10,000/kg today. Phase II will build and test a prototype sizing device, build a full-size sizing system (with kg/hour output), and evaluate its performance. Kilogram quantities of powders from four commercial superconductor manufacturers will be processed, and the superconducting performance of the resulting wire will be tested. Commercial Applications And Other Benefits as described by the awardee: The removal of large particles from superconducting powders should make it feasible to make higher performance wire, with lower losses and better properties. In addition, a quite different application was identified for the technology: separating particle sizes for titanium oxide powder used in sun block ¿ a rapidly growing market. Although titanium oxide is the most effective UV-absorbing powder its white color makes a pasty appearance on the skin when enough is loaded in an ointment to provide total protection. However, if the powder is ground to a size of 1-2 microns, it becomes invisible, yet still effective for UV absorption. This separation technology appears to be the only possibility yet devised that could separate commercial quantities of titanium oxide powder for the sun block application.