Fine Powder Production Using Electrohydrodynamic Atomization

Abstract

A method for producing ultrafine powders by electrohydrodynamic (EHD) atomization is described. The tip of a consumable electrode (fine wire or rod) is melted by means of electron bombardment. Atomization of the molten wire tip material is accomplished by applying high potentials to the wire feedstock. The expended material is replenished by an automatic wire feed mechanism. The process produces high-quality ultraclean spherical powders, extending the lower range of particle sizes available from conventional atomization methods. This new process avoids many problems associated with EHD atomization employing nozzle and reservoir components. The process provides crucibleless melting, contamination-free powders, and the ability to process high-temperature material (>3000°C). Although currently a laboratory process, this fine powder technology has scaling potential for producing powders of engineering significance. Materials which can be processed by this technology include metals (e.g., Ta, Mo, and metals which are corrosive in the liquid state such as Ti or U), alloys, ceramics, and ceramic-metal combinations. The availability of powder in the form of micrometer and submicrometer spherical particles opens new vistas for material processing applications. The advantages anticipated include controlled microstructures, including rapidly solidified features, amorphous or fine-grained morphologies, material with properties that approach the ideal sinterable powder, and powders with large surface area per unit mass for surface active or dispersive behavior. Potential areas of application include powders for catalysis, injection molding, thick-film pastes, film processing, conductive pastes, and adhesives.