Carbothermic reduction of molybdenum oxide in vacuum

Molybdenum has received considerable attention as engineering materials for heat engine applications. In this study, the possibilities and conditions for winning the pure molybdenum by the carbothermic reduction of MoO2 in vacuum have been examined with regard to the following items: (1) Working conditions and analytical results on the molybdenum obtained by this process. (2) Measurements of solid solubility of oxygen in molybdenum. (3) Vacuum degassing in solid state and evaporation deoxidation in the form of MoO3. The mechanism of refining of the molybdenum metal by the present method can be characterized by the following steps. Carbon is removed by degassing as CO and the elimination of oxygen takes place in the form of CO and volatile oxides such as MoO3 and MoO2. Both phenomena seem to occur during the refining period in the solid state under vacuum at around 2273 K. Accordingly, the carbon elimination is possible only when an excess of oxygen is present. On the other hand, even after the decrease of carbon, the remaining oxygen can be removed by the oxide evaporation. With this process the high purity molybdenum in which both carbon and oxygen contents are reduced to a sufficient degree is obtainable by favorable conditions of reduction. (author)