Niobium powder production by reducing electrochemically dissolved niobium ions in molten salt

Abstract

A new niobium (Nb) powder production process based on the reduction of electrochemically dissolved niobium ions (Nb n+ ) by dysprosium divalent ions (Dy 2+) in the NaCl–KCl–MgCl 2–DyCl 2 molten salt was investigated. Nb n+ ions – feed material – were continuously supplied into the molten salt by the anodic dissolution of a Nb rod. They were subsequently reduced in situ by Dy 2+ ions – reductant – in the salt to produce Nb powder. The Dy 3+ ions generated were reduced to Dy 2+ ions by electrochemical or magnesiothermic reduction at the cathode (liquid Mg–Ag alloy). Fine and uniform Nb powder with a purity of around 99 mass% was successfully obtained under a specific condition. Further, it was found that the reaction time had a small influence on the particle size of the powder. A possible reaction pathway of the reduction of Nb n+ ions by Dy 2+ ions in the molten salt was discussed with the aid of an isothermal chemical potential diagram of the Nb–Dy–Cl system at 1000 K.