Method for Combination Solid State and Molten Salt Tantalum Reduction

Abstract

A two-phase reduction method for producing tantalum powder includes loading an unheated reaction vessel with a layer of K 2 TaF 7 , then a layer of solid sodium metal, and then followed by a layer of solid diluent salt. A first heating phase is used to promote the solid state reduction of the layer of K 2 TaF 7 , which results in the production of very fine tantalum particles while minimizing tantalum crystal growth. A second heating phase is then used to melt the contents of the reactor vessel and react primary quantities of sodium metal and K 2 TaF 7 to produce tantalum powder. In certain embodiments, the fine tantalum particles produced during the first heating phase serve as the nucleation sites needed for tantalum crystal growth in the second heating phase.

1 . A method for producing tantalum powder comprising:
 loading an unheated first reactor vessel with a layer of solid potassium tantalum fluoride (K 2 TaF 7 );   loading the unheated first reactor vessel with a layer of solid sodium metal over the layer of solid K 2 TaF 7 ;   loading the unheated first reactor vessel with a layer of solid diluent salt over the layer of solid K 2 TaF 7  and the layer of solid sodium metal;   heating the first reactor vessel to a first phase temperature to promote a solid state reduction of the layer of K 2 TaF 7 ;   heating a second reactor vessel to a second phase temperature sufficient to melt the previously-loaded K 2 TaF 7 , solid sodium metal and solid diluent salt;   adding primary quantities of sodium metal and K 2 TaF 7  to the reactor vessel; and   reacting the primary quantities of sodium metal and K 2 TaF 7  to produce tantalum powder.   
     
     
         2 . The method of  claim 1 , wherein the second reactor vessel is the first reactor vessel. 
     
     
         3 . The method of  claim 1 , wherein the second reactor vessel is different than the first reactor vessel, and wherein the method further comprises transferring, after said heating the first reactor vessel, the previously-loaded K 2 TaF 7 , solid sodium metal and solid diluent salt to the second reactor vessel. 
     
     
         4 . The method of  claim 1 , wherein the layer of solid K 2 TaF 7  comprises between about 1 Kg and about 200 Kg of solid K 2 TaF 7 . 
     
     
         5 . The method of  claim 1 , wherein the layer of solid sodium metal comprises between about 0.5 Kg and about 100 Kg of metallic sodium. 
     
     
         6 . The method of  claim 1 , wherein the first phase temperature is between about 200° C. and about 300° C. 
     
     
         7 . The method of  claim 1 , wherein the second phase temperature is between about 650° C. and about 1000° C. 
     
     
         8 . The method of  claim 7 , wherein the second phase temperature is between about 650° C. and about 900° C. 
     
     
         9 . The method of  claim 1 , adding the primary quantities of sodium metal and K 2 TaF 7  comprises incrementally adding sodium metal and K 2 TaF 7  to the second reactor vessel. 
     
     
         10 . The method of  claim 1 , further comprising agitating the primary quantities of sodium metal and K 2 TaF 7  in the second reactor vessel while heating the second reactor vessel to a second phase temperature. 
     
     
         11 . The method of  claim 1 , wherein loading the unheated first reactor vessel with the layer of solid sodium metal comprises loading the first reactor vessel with an excess quantity of solid sodium metal for complete reduction of the layer of solid K 2 TaF 7 . 
     
     
         12 . The method of  claim 1 , wherein the unheated first reactor vessel has an internal temperature of below approximately 100° C. 
     
     
         13 . The method of  claim 1 , wherein a plurality of discrete tantalum particles are produced as a result of the solid state reduction of the layer of K 2 TaF 7 , and wherein the plurality of discrete tantalum particles are each submicron in size. 
     
     
         14 . The method of  claim 13 , wherein reacting the primary quantities of sodium metal and K 2 TaF 7  comprises forming tantalum crystals on a plurality of nucleation sites, wherein the plurality of nucleation sites comprises the plurality of discrete tantalum particles produced from the solid state reduction of the layer of K 2 TaF 7 . 
     
     
         15 . A two-phase method for producing tantalum powder comprising:
 loading an unheated reactor vessel with an initial quantity of solid potassium tantalum fluoride (K 2 TaF 7 );   loading the unheated reactor vessel with an initial quantity of solid sodium metal;   loading the unheated reactor vessel with an initial quantity of solid diluent salt;   providing a first heating phase during which the reactor vessel is heated to a first phase temperature sufficient to promote a solid state reduction of the initial quantity of K 2 TaF 7 ;   providing a second heating phase during which the reactor vessel is heated to a second phase temperature sufficient to melt said initial quantities in the reactor vessel; and   introducing a primary quantity of sodium metal and a primary quantity of K 2 TaF 7  to the reactor vessel during the second heating phase, wherein the primary quantities of sodium metal and K 2 TaF 7  react during the second heating phase to produce tantalum powder.   
     
     
         16 . The method of  claim 15 , wherein providing the first heating phase comprises providing the first heating phase in a first reactor vessel, and wherein providing the second heating phase comprises providing the second heating phase in a second reactor vessel. 
     
     
         17 . The method of  claim 15 , wherein the initial quantity of solid K 2 TaF 7  comprises between about 1 Kg and about 200 Kg. 
     
     
         18 . The method of  claim 15 , wherein the initial quantity of solid sodium metal comprises between about 0.5 Kg and about 100 Kg. 
     
     
         19 . The method of  claim 15 , wherein the first phase temperature is between about 200° C. and about 300° C. 
     
     
         20 . The method of  claim 15 , wherein the second phase temperature is between about 650° C. and about 1000° C. 
     
     
         21 . The method of  claim 20 , wherein the second phase temperature is between about 650° C. and about 900° C. 
     
     
         22 . The method of  claim 15 , wherein introducing the primary quantities of sodium metal and K 2 TaF 7  comprises incrementally adding sodium metal and K 2 TaF 7  to the reactor vessel. 
     
     
         23 . The method of  claim 15 , further comprising agitating the primary quantities of sodium metal and K 2 TaF 7  in the reactor vessel during the second heating phase. 
     
     
         24 . The method of  claim 15 , wherein the initial quantity of solid sodium metal comprises an excess quantity of solid sodium metal for complete reduction of the initial quantity of solid K 2 TaF 7 . 
     
     
         25 . The method of  claim 15 , wherein the unheated reactor has an internal temperature of below approximately 100° C. 
     
     
         26 . The method of  claim 15 , wherein a plurality of discrete tantalum particles are produced during the first heating phase, and wherein the plurality of discrete tantalum particles are each submicron in size. 
     
     
         27 . The method of  claim 26 , further comprising forming tantalum crystals on a plurality of nucleation sites during the second heating phase, wherein the plurality of nucleation sites comprise the plurality of discrete tantalum particles produced during the first heating phase. 
     
     
         28 . A capacitor component comprising the tantalum powder manufactured according to the method of  claim 1 . 
     
     
         29 . A capacitor component of  claim 28 , wherein said capacitor component comprises a capacitor anode.