Kazuyoshi Shimakage1, Tadao Sato1, Shinji Hirai1,Shigeo Toda1, Touru Takahasi2 and Youichi Sakuta2
1Department of Materials Science and Technology, Muroran Institute of Technology, Muroran
Crude niobium has been purified by a refining process consisting of molten salt electrolysis and electron beam melting. The molten salt electrorefining was carried out galvanostatically using a FLINAK bath (26.3 mass%LiF-10.5 mass%NaF-47.0 mass%KF-16.2 mass%K2NbF7) at 963 K under Ar atmosphere. After the molten salt electrorefining and the electron beam melting, the contents of metallic impurity components in the purified niobium were determined by ICP emission spectrography analysis. Refractory metals such as tantalum, tungsten and molybdenum in crude niobium could be eliminated by means of molten salt electrorefining. Especially, the molten salt electrorefining method using fluoride bath was remarkably effective for the removal of metallic tantalum in crude niobium. Nonmetallic impurity components such as oxygen and nitrogen could be also removed by electron beam melting.
Crude niobium of 99.8 mass% purity was found to be purified to 99.99 mass% by this refining process.
(Received March 20, 1995)
molten salt electrolysis, electron beam melting, crude niobium, purification, high purity
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