Method to agglomerate metal particles and metal particles having improved properties

Abstract

A method to agglomerate metal particles such as tantalum and niobium powders is described which includes combining a volatilizable or vaporizable liquid with the particles to form wet particles; compacting the wet particles; drying the compacted wet particles to form a cake; and heat treating the cake to form the agglomerated particles. Also described are agglomerated particles obtained by this method and further, particles, preferably tantalum or niobium powder, having a flow rate of at least about 65 mg/sec and/or an improved pore size distribution, and/or a higher Scott Density. Capacitors made from tantalum powder and niobium powder are also described.

What is claimed is:  
     
         1 . A method to agglomerate tantalum or niobium particles or both comprising: 
 a) combining a volatilizable or vaporizable liquid with particles comprising tantalum, niobium, or both to form wet particles;    b) compacting the wet particles;    c) drying the wet compacted particles to form a cake; and    d) heat treating the cake.    
     
     
         2 . The method of  claim 1 , wherein said compacting is accomplished by vibrating said wet particles in a container.  
     
     
         3 . The method of  claim 1 , wherein said compacting is accomplished by applying pressure to said wet particles.  
     
     
         4 . The method of  claim 1 , wherein said liquid is water.  
     
     
         5 . The method of  claim 1 , wherein said water is deionized water.  
     
     
         6 . The method of  claim 1 , wherein before said compacting, said particles soak in the liquid for at least five hours.  
     
     
         7 . The method of  claim 1 , wherein before said compacting, said particles soak in the liquid for at least eight hours.  
     
     
         8 . The method of  claim 1 , wherein said drying occurs for at least 10 hours.  
     
     
         9 . The method of  claim 1 , wherein said drying occurs for at least 14 hours.  
     
     
         10 . The method of  claim 1 , wherein said liquid is present in an amount of from about 30% to about 50% by weight of particles.  
     
     
         11 . The method of  claim 1 , wherein said liquid is added in an amount of about 40% by weight of particles.  
     
     
         12 . The method of  claim 1 , wherein the cake is deagglomerated after heat treating.  
     
     
         13 . The method of  claim 1 , said particles have pores, and wherein before said vibrating, the particles soak in the liquid for a time sufficient to allow the liquid to substantially fill the pores of the particles.  
     
     
         14 . The method of  claim 1 , wherein the particles are tantalum particles.  
     
     
         15 . The method of  claim 1 , wherein the particles are niobium particles.  
     
     
         16 . The method of  claim 1 , wherein the particles comprise tantalum particles.  
     
     
         17 . The method of  claim 1 , wherein the metal particles comprise niobium particles.  
     
     
         18 . The method of  claim 1 , wherein the liquid comprises water.  
     
     
         19 . The method of  claim 1 , wherein the liquid comprises water and phosphoric acid.  
     
     
         20 . The method of  claim 1 , wherein the liquid comprises water and from about 10 ppm to about 100 ppm of phosphorous.  
     
     
         21 . The method of  claim 1 , wherein the liquid comprises water and an inorganic acid.  
     
     
         22 . The method of  claim 1 , wherein the liquid is present in an amount of from about 10% to about 50% by weight of particles.  
     
     
         23 . The method of  claim 1 , wherein the liquid is present in an amount to form a paste consistency with the particles.  
     
     
         24 . The method of  claim 1 , further comprising the step of adding additional volatilizable or vaporizing liquid to the container while the container is being vibrated.  
     
     
         25 . The method of  claim 1 , wherein said drying is accomplished in a vacuum dryer.  
     
     
         26 . The method of  claim 1 , wherein said drying occurs at a temperature of from about 180° F. to about 225° F.  
     
     
         27 . The method of  claim 1 , wherein said drying occurs at a temperature of from about 180° F. to about 225° F. and a vacuum pressure of from about 20 torr to about 50 torr.  
     
     
         28 . The method of  claim 1 , wherein a liquid drying forms on top of the wet particles, before or after compacting.  
     
     
         29 . The method of  claim 28 , wherein about 0.125 ml/cm 2  of water forms on top of the wet particles based on the square area of a container containing the particles.  
     
     
         30 . Agglomerated particles obtained by the method of  claim 1 .  
     
     
         31 . Agglomerated particles obtained by the method of  claim 2 .  
     
     
         32 . Agglomerated particles obtained by the method of  claim 3 .  
     
     
         33 . Particles comprising tantalum, niobium, or both, having a flow rate of at least about 65 mg/sec and a pore size distribution greater than unagglomerated particles.  
     
     
         34 . The particles of  claim 33 , wherein said particles have a flow rate of at least about 100 mg/sec.  
     
     
         35 . The particles of  claim 33 , wherein said particles have a flow rate of at least about 150 mg/sec.  
     
     
         36 . The particles of  claim 33 , wherein said particles have a flow rate of at least about 175 mg/sec.  
     
     
         37 . The particles of  claim 33 , wherein said particles have a flow rate of at least about 200 mg/sec.  
     
     
         38 . The particles of  claim 33 , wherein said particles comprise niobium.  
     
     
         39 . The particles of  claim 33 , wherein said particles comprise tantalum.  
     
     
         40 . The particles of  claim 33 , wherein said pore size distribution is greater than unagglomerated particles by at least 10% with respect to greater diameter pores.  
     
     
         41 . The particles of  claim 33 , wherein said particles are nodular tantalum powder.  
     
     
         42 . The particles of  claim 33 , wherein said particles are nodular niobium powder.  
     
     
         43 . The particles of  claim 41 , wherein said particles have a Scott Density of at least 20 g/inch 3 .  
     
     
         44 . The particles of  claim 41 , wherein said particles have a Scott Density of about 20 g/inch 3  to about 40 g/inch 3 .  
     
     
         45 . A capacitor component comprising the tantalum powder of  claim 39 .  
     
     
         46 . A capacitor component comprising the niobium powder of  claim 38 .  
     
     
         47 . The capacitor component of  claim 45 , wherein said component is a capacitor anode.  
     
     
         48 . The capacitor component of  claim 46 , wherein said component is a capacitor anode.  
     
     
         49 . A method to agglomerate metal particles comprising: 
 a) combining a volatilizable or vaporizable liquid with metal particles to form wet particles;    b) compacting the wet metal particles;    c) drying the wet compacted metal particles to form a cake; and    d) heat treating the cake.    
     
     
         50 . A method to agglomerate metal particles comprising: 
 a) combining a volatilizable or vaporizable liquid with particles comprising wet metal particles;    b) vibrating the wet particles;    c) drying the wet metal particles to form a cake; and    d) heat treating the cake.