Method and an apparatus of plasma processing of tantalum particles
View Patent ↗Porous microparticles of high-purity tantalum may be processed in a vacuum plasmatron using a hollow cathode and spraying apparatus in which the coolant is in the form of a metal surface. In one embodiment, the initial powder of tantalum is introduced through a coaxial hole in a hollow cathode and supplied to a vertical column of plasma by inert gas and exposed to heating to temperatures close to the melting point of tantalum. The atomizing tantalum particles are directed through a hole in the anode and collide with a rotating inclined tantalum substrate and cooled from within water, thereby flattened and solidifying the particles.
1. A method for processing tantalum powder particles comprising:
feeding tantalum powder particles and an inert gas into a hollow cathode of a vacuum chamber;
generating a plasma arc between the hollow cathode and an anode oriented below the hollow cathode;
heating said tantalum powder particles to a predetermined temperature within said plasma arc;
accelerating said tantalum powder particles towards an orifice of the anode using an electric field between the hollow cathode and the anode; and
impacting a cooling surface with said tantalum powder particles, wherein the cooling surface is located on a side of the anode opposite to the hollow cathode.
2. The method of claim 1 , wherein said inert gas comprises argon gas, and wherein feeding comprises feeding said tantalum powder particles and argon gas into a zirconium cylinder oriented within an opening of said hollow cathode.
3. The method of claim 1 , wherein said predetermined temperature corresponds to a thermoemission temperature of said tantalum powder particles.
4. The method of claim 1 , wherein impacting the cooling surface comprises impacting a water-cooled surface having one of an ellipse shape and a cone shape.
5. The method of claim 1 , wherein said impacting comprises impacting the cooling surface such that tantalum powder particles deform to a flake-like shape.
6. The method of claim 1 , further comprising rotating said cooling surface so as to generate a centrifugal force that directs said that tantalum powder particles to a collector.
7. The method of claim 1 , further comprising directing said tantalum powder particles to a position in the plasma arc and maintaining said position using the electric field for a period of time that is a function of one or more of an efficiency of thermoemission, ionic purification, and activation of a surface of the tantalum powder particles.
8. The method of claim 1 , wherein said cooling surface comprises a top layer of tantalum.