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 K2TaF7, 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 K2TaF7, 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 K2TaF7 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.

Description

FIELD OF THE INVENTION[0001]The present disclosure relates generally to tantalum reduction products and, more particularly, to a method for the reduction of tantalum using a combination solid state and molten salt tantalum reduction so as to control undesirable crystal growth in order to optimize the particle size distribution of tantalum powder.BACKGROUND OF THE INVENTION[0002]With evolution and microminiaturization of microprocessors and other electronics, the need for high-capacitance tantalum capacitors has rapidly increased. Moreover, the demands on purity and surface area for use in electrolytic capacitors are very high.[0003]In order to satisfy the need in the art for high-purity tantalum powder, potassium tantalum fluoride (K2TaF7) is generally reduced using sodium metal so as to form tantalum powder. One of the key qualities of tantalum powder is that it should have a very narrow particle size distribution. The optimum median particle size is a function of the intended form...

AI Technical Summary

Benefits of technology

[0006]Disclosed and claimed herein are methods for producing tantalum powder. In one embodiment, a method includes loading an unheated reactor vessel with a layer of solid K2TaF7, loading the unheated reactor vessel with a layer of solid sodium metal over the layer of solid K2TaF7, and then loading the unheated reactor vessel with a layer of solid diluent salt over the layer of solid K2TaF7 and the layer of sol

Problems solved by technology

Moreover, the demands on purity and surface area for use in electrolytic capacitors are very high.

However, one of the problems with producing tantalum powder having a uniform particle size is that a sodium reduction reaction of K2TaF7 is highly exothermic, with the reaction rate increasing as temperature increases.

This is significant since both temperature and reaction rate tend to have a negative effect on the uniformity of tantalum crystal growth, which in turn directly affects the uniformity of the resulting tantalum particles produced.

However, none of the prior art techniques are able to adequately control crystal growth such that the particle size distribution for the tantalum powder is optimized.

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