Making of tantalum powder using the hunter process

Tantalum powder was made from potassium heptafluorotantalate (K ₂TaF₇) using sodium as a reductant based on the Hunter metallothermic reduction method. The apparatus for the experiment was designed and built specifically for the present study. The tantalum particle size greatly decreased as the reduction temperature decreased from 860 to 740°C. The particle size was fairly uniform, varying from 2-3 μm to submicron sizes depending on the reaction temperature. Holding the reactants for more than 10 minutes after the completion of a sodium feeding caused irregular particle growth, thereby affecting particle size uniformity. It was found to be possible to agglomerate the powder to tens of micrometers in size by a vacuum heat treatment at 1350°C. The formation of Ta₂C during the heat treatment shows that care must be taken to prevent contamination from the furnace environment.