High-speed fabrication of highly uniform metallic microspheres

Abstract

In a high-speed fabrication process for producing highly uniform metallic microspheres, a molten metal is passed through a small orifice, producing a stream of molten metal therefrom. A series of molten metal droplets forms from the break up of the capillary stream. To achieve high uniformity of the spheres and avoid defects, the droplets are cooled before being captured. Separating the droplets, by causing them to travel in different paths than their adjacent droplets, helps to facilitate the cooling of the droplets. The droplets can be separated by electrostatically charging them as they break off from the capillary stream. The droplets are then passed through an electric field, which can be produced by a pair of deflection plates. The droplets are dispersed by varying the electric field—e.g., by rotating the plates or by varying the voltage applied thereto—or by varying the electrostatic charge of the droplets. Advantageously, the droplets can be actively cooled in flight by passing them through a cryogenic gas chamber.