Mechanisms Underlying Phase Transition and Regulation of Tantalum Powder Properties During Magnesium Thermal Reduction of Ta2O5 in a Molten Salt Medium

Magnesium reduction of Ta₂O₅ (tantalum pentoxide) is a metallurgical process widely used to extract metallic tantalum powder from its oxide form using magnesium as a reducing agent in a molten salt medium. This study explores the mechanisms and patterns of phase transformation during the magnesium reduction of Ta₂O₅ in a molten salt medium, focusing on the influence of temperature and time on the physical and chemical properties of the resulting tantalum powder. The results reveal that under various reaction conditions in a molten salt medium, the magnesium reduction of Ta₂O₅ follows four distinct pathways: Ta₂O₅ → Ta, Ta₂O₅ → MgTa₂O₆ → Ta, Ta₂O₅ → MgTa₂O₆ → Mg₄Ta₂O₉ → Ta, and Ta₂O₅ → Mg₄Ta₂O₉ → Ta. Each pathway significantly affects the physical and chemical properties of the resulting tantalum powder. Using a uniform mixing method, the reaction proceeds directly from Ta₂O₅ to Ta powder in a single step. As the reaction temperature increases from 600 °C to 900 °C, the average particle size of the tantalum powder enlarges from 30 nm to 150 nm, with the product phase transitioning from a mixture of Ta and Ta₂O to a single Ta phase. Additionally, prolonged holding time improves the uniformity of the tantalum powder's particle distribution. This study accomplishes directional control over the phase transformation and the properties of tantalum powder during the reduction process, thus offering valuable guidance for the preparation of high-performance tantalum powder.