Uniform solid and hollow metal spheres: Formation in a pulsed micro-arc and applications

A novel process for producing monodisperse metal spheres with diameters from 50 to 1000 μm has been developed. The process involves melting a consumable wire-electrode in a pulsed micro-arc, so that a single metal droplet is formed and separated in each pulse. Subsequent droplet cooling determines the final properties of the metal spheres. Control of the droplet initial temperature from the melting to the boiling point, together with variation of the cooling medium, allows production of metal spheres with unique properties, e.g., solid, internally oxidized, or hollow granules. Uniform diameter spherical particles of Al, Cu, Mo, Ni, Ta, W, Ti, Zr, and some alloys such as stainless steel, nichrome, monel, have been produced. Applications of the process include production of uniform spherical metal particles for metal combustion studies, development of a novel droplet welding technique, and production of particles for experimental simulation of micrometeoroid-surface interactions. Other possible uses may be in energy-absorbing structures, composite materials, metal micro-dosing, and micro-mechanical device production.