Effects of Oxide Precursor Preparation Parameters on the Electrochemical Reduction of Tantalum Pentoxide in Calcium Chloride Melt

摘要

Successful electrochemical reduction of a metal oxide to its constituent metal depends upon two broad unit operations: (i) preparation of the oxide precursor with ideal morphological features and (ii) electrochemical reduction under optimum process parameters. The critical parameters that affect mechanical strength and open porosity of the precursor are oxide particle size; green pellet preparation; and sintering time, temperature, and atmosphere. A judicious combination of these process parameters will produce an ideal precursor for achieving complete reduction. Uniaxial pressing was utilized to prepare 13 mm diameter cylindrical pellets, which were sintered in either oxidizing (air) or reducing atmospheres. Sintered pellets were characterized by XRD, SEM-EDS, and porosity measurement techniques. Electrochemical reduction experiments were performed with a molten calcium chloride electrolyte in a cell with a three electrode configuration. Transient electrochemical techniques were employed to assess the effects of the precursor parameters on the reducibility of the sintered oxide specimens.