The Preparation of Tantalum Metal by the Carbon Reduction of Tantalum Pentoxide

A mixture of tantalum pentoxide and carbon when heated under vacuum conditions reacts to give carbon monoxide as essentially the only gaseous product. A temperature of about 1200° C is required to give measurable gas evolution. The degree of completion of the reaction for a certain charge and for a certain finishing pressure depends upon the temperature. In a uniform stoichiometric mixture of fine powders, the reaction goes to near completion at a temperature of about 2100° C with a finishing pressure of less than one micron. The carbon in the charge appears to be in the form of carbides at intermediate stages of the reaction. The metal is recovered from the reduction step in the form of a sponge. Solid ingots are formed by arc melting the sponge. Excess carbon (over stoichiometric) in the charge remains in the final metal as carbide. Excess oxygen can be removed by heating the metallic sponge product to about 2400° C in in a vacuum. It appears that under these conditions the oxygen is volatilized as TaO2. The conditions for reaction and removal of excess oxygen suggest a method for metal preparation