Production of Fine Tantalum Powder by Electrochemical Method

Abstract

A fundamental study on producing fine tantalum powder by reducing electrochemically dissolved tantalum ions (Ta n+ ) by dysprosium divalent ions (Dy 2+ ) in molten salt was investigated in order to develop a new process for pulverizing a tantalum ingot to fine powder for electronic devices. A tantalum rod (anode) was immersed in the NaCl-KCl-MgCl 2 -DyCl 2 molten salt at 1000K, and it was anodically dissolved in this salt. The electrochemically dissolved Ta n+ ions were subsequently reduced in situ by Dy 2+ ions in the molten salt to produce tantalum powder. The reaction product, Dy 3+ ions, generated during the production of tantalum powder, were reduced by either electrochemical or magnesiothermic reduction at the cathode (liquid Mg-Ag alloy) and regenerated to reductant Dy 2+ ions. Fine and uniform tantalum powder with an average particle size of around 0.1 μm was directly and successfully obtained from the bulk tantalum under a specific condition. A possible reaction pathway for the reduction of Ta n+ ions by Dy 2+ ions in the molten salt was discussed with the aid of an isothermal chemical potential diagram of the Ta-Dy-Cl system at 1000 K.