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

The preparation of high purity (greater than 99.8%) ductile grade vana dium is extremely difficult owing to its exceptionally high affinity t owards carbon, nitrogen and oxygen. The removal of these interstitial impurities by conventional melt-refining routes is rather difficult. S pecialized techniques such as pyrovacuum treatment, iodide decompositi on and fused salt electrorefinement are normally adopted to prepare ul trapure vanadium. In the present investigation a new technique which i nvolves the preparation and subsequent thermal decomposition of vanadi um nitride (VN) has been attempted to obtain vanadium metal. The vanad ium nitride in this study was prepared by carbonitrothermic reduction of vanadium pentoxide (V2O5) at a temperature of 1500-degrees-C. The V N thus formed was thermally decomposed at 1750-degrees-C under reduced pressure (3 x 10(-2) Pa) to metallic vanadium. Consolidation of the p roduct 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, leadin g to a purity better than 99.5%.