Powder Densification and Spheroidization Using an Axisymmetric Microwave Generated Plasma

Amastan has developed an innovative process for powder particle densification and spheroidization using its novel microwave plasma technology. It consists of transforming angular and rugged powders particles, or porous spray dried powders into dense and free flowing spherical powders which are required in as thermal spray coatings, or powder injection molding. Powder densification/spheroidization process improves powder flowability, increases particle density, overall powder tap density, and purity.

Uniform volumetric heating and melting of rugged particles is essentially due to the homogeneity of the plasma hot zone where a uniform melt state for a particle is produced by Amastan’s microwave based plasma process (UniMelt™). Its main features include axial injection of feedstock into an axisymmetric hot zone with high and uniform profile plasma temperature, laminar gas flows, and high heating rates. Consequently, all particles are processed along a uniform thermal path. The hot zone is electrode free, which eliminates the presence of contaminants in the final product. Coupling efficiency of microwave plasma to the microwave source energy exceeds 95% and makes UniMelt a much more cost efficient spheroidization process than, for instance, the Radio Frequency (RF) induction plasma process.

In addition to spheroidization of solid powder particles as feedstock, UniMelt™ can also be used for a single step production of dense and spherical particles through the injection of solution precursors. In particular, Amastan uses a droplet maker capable of generating uniform diameter precursor droplets with narrow size distribution that are injected into UniMelt™ for the production of equal diameter, dense, and spherical powder particles. These droplets undergo rapid pyrolysis, followed by melting, and then solidification in one step as they are processed through UniMelt™.  This rapid processing could be of great interest to the coating industry and powder metallurgy as well, especially when uniformly sized and dense powder particles are desired.