METHODS FOR SPHERICALLY GRANULATING AND AGGLOMERATING METAL PARTICLES AND THE METAL PARTICLES PREPARED THEREBY, ANODES MADE FROM THE METAL PARTICLES

A method for spherically granulating and agglomerating metal particles such as tantalum and/or niobium powders is described in the present invention, which includes the steps of: a). comminuting the metal particles to form fine particles having D50 less than 50 μm; b). granulating the comminuted metal particles comprising volatile liquid, for example, tantalum and/or niobium particles comprising volatile liquid, to form wet spherical particles; c). still drying the wet spherical particles and removing volatile liquid to form flowable pre-agglomerated particles with increased bulk density; d). heat treating the pre-agglomerated particles; e). screening the heat treated powder to obtain the flowable agglomerated particles. The present invention provides a flowable spherical agglomerated metal particles, and especially tantalum and/or niobium particles having improved properties. The present agglomerated tantalum powder have a flow rate of at least about 2.0 g/sec, a BET surface area of from about 0.2 to about 6.0 m2/g, a FSSS of at least 1.0 μm, a Scott bulk density of from about 1.2 g/cm3 to about 5.5 g/cm3. The present agglomerated niobium powder have a flow rate of at least about 1.0 g/sec, a BET surface area of from about 0.5 to about 8.0 m2/g, a FSSS of at least 1.0 μm, a Scott bulk density of from about 0.7 g/cm3 to about 3.5 g/cm3. Said tantalum and/or niobium metal particles have improved pore size distribution of the sintered anodes and increased pellet crush strength. The present invention further provides an electrolytic capacitor anodes made from the tantalum and/or niobium particles according to the present invention having a capacitance of from about 5,000 μFV/g to about 300,000 μFV/g.