バナジウムおよびバナジウム合金の新しい製造技術の開発

Abstract

The abundance of vanadium (V) in the earth's crust is 150 ppm; this is significantly larger than the abundance of nickel, zinc, or copper which are classified as common metals. However, V metal belongs to a set of “less-common metals” or “rare metals” because of the small production volume. This fact is partly due to its low concentration in its natural ores and the uneven distribution of its minerals. V metal is commercially produced by the aluminothermic reduction (ATR) of vanadium pentoxide (V2O5). The reduction product of the ATR process is a vanadium-aluminum (V-Al) alloy containing approximately 20 mass% of aluminum. Further purification process is required for obtaining pure V metal, used for the fabrication of functional materials such as hydrogen storage alloys. At this stage, an effective production process of pure V metal has not been established. Therefore, there is a strong requirement for the development of a simple and efficient process for the direct production of high-purity V metal and its alloy. This paper reviews various types of processes for producing V metal and its alloys. These reduction processes are classified on the basis of the V compounds and reaction types, and their features are reviewed. Lastly, the future prospects for the development of new processes for the production of high-purity V metal are presented.