Abstract
A new vanadium intermediate, containing 94·4% vanadium, was successfully electrorefined to a purity of 99·8 mass-% in CaCl2–NaCl–VCl2 electrolyte. The impure vanadium was prepared by heating a mixture of vanadium pentoxide (V2O5) and graphite powder under flowing nitrogen atmosphere. Vanadium nitride, so prepared, was subjected to pyrovacuum heating to a temperature of 1750°C under dynamic vacuum (better than 0·05 Pa) to prepare vanadium sponge. The impure vanadium was then taken up for further refining in a molten salt electrolytic bath. The cathode current efficiency and metal recovery, under optimised conditions, were found to be 90 and 87% respectively. The hardness of the arc cast vanadium crystals (with a size ⩾840 μm) indicated the formation of a ductile grade vanadium metal. Scanning electron microscopy photographs of the coarse crystallites showed a dendritic morphology, consisting of primary, secondary, tertiary and quaternary branching.
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