PREPARATION OF VANADIUM NITRIDE AND ITS SUBSEQUENT METALLIZATION BY THERMAL-DECOMPOSITION

The preparation of high purity (greater than 99.8%) ductile grade vanadium is extremely difficult owing to its exceptionally high affinity towards carbon, nitrogen and oxygen. The removal of these interstitial impurities by conventional melt-refining routes is rather difficult. Specialized techniques such as pyrovacuum treatment, iodide decomposition and fused salt electrorefinement are normally adopted to prepare ultrapure vanadium. In the present investigation a new technique which involves the preparation and subsequent thermal decomposition of vanadium nitride (VN) has been attempted to obtain vanadium metal. The vanadium nitride in this study was prepared by carbonitrothermic reduction of vanadium pentoxide (V2O5) at a temperature of 1500-degrees-C. The VN thus formed was thermally decomposed at 1750-degrees-C under reduced pressure (3 x 10(-2) Pa) to metallic vanadium. Consolidation of the product metal sponge (by arc melting) under a low pressure, high purity argon atmosphere yielded vanadium of purity better than 97%. The arc-melted metal can be further refined by fused salt electrolysis, leading to a purity better than 99.5%.