Preparation and Properties of Fine Diameter Multifilament Niobium Carbonitride Super-conducting Fibers.

摘要

This report summarizes the development efforts on niobium carbonitride yarn. The preparation was accomplished by reacting the carbon fiber precursor with niobium pentachloride in the presence of hydrogen and nitrogen at 1500to 1600C for 2to 6minutes. The reacted yarn was quenched from the reaction temperature to about 200C to retain the niobium carbonitride phase. These fibers display excellent superconducting properties. A post treatment with ammonia was found to cause a composition change yielding a nitrogen rich product via a further nitriding process. The critical current and current density of the typical products were increased. Silicon dopant was found to be effective in improving the critical current at high magnetic fields. Improvement in electrical contact between the superconductor and copper coating was accomplished by a post coating heat treatment in the temperature range of 600to 1000C in the inert atmosphere. (Modified author abstract)