Silver supports superconducting paste.

Silver supports superconducting paste

Like children in front of a closed candy store, superconductor scientists have their noses pressed against the window of a largely inaccessible technology sweetshop. Since the 1987 announcement of ceramic compounds that superconduct at liquid-nitrogen temperatures, visions of cheaper, cleaner energy production, magnetically levitated trains and exotic technologies have filled scientists' imaginations. But visions these will remain until researchers find reliable ways to transform the brittle, rock-like materials into more rugged, practical forms such as superconducting wires.

Silver may provide an answer, according to scientists at the Argonne (Ill.) National Laboratory. Grinding silver powder with the superconducting ceramic material and mixing these ingredients with methanol or isopropyl (rubbing) alcohol yields a slurry that the researchers spread evenly onto paper-thin ribbons of silver foil. Before firing the composite into its final, hardened form, the scientists can bend it, even into coils. The heat treatment joins the two layers of the assembly by causing silver particles in the slurry to bond with the silver of the ribbon backing. The metal fills tiny cracks that form during processing and also can shuttle current through or around such imperfections, the researchers say.

"At this stage, we are toying around," remarks Argonne's Balu Balachandran. The crude, silver/superconductor composite cannot yet carry enough current to serve much practical purpose, he says. Still, he adds, the project shows there are ways of working ceramic materials into complex shapes and gives reason to believe that some of the fantastic visions for superconductors may become reality.