Metal nanopowder production by cryogenic mechanical collision and pulsed electric discharge methods

Abstract

With the introduction of micro and nanosensors and devices, the need for pure metal and ceramic powders have risen. Spherical pure metal powders and their alloys are vital raw materials for near-net-shape fabrication via powder-metallurgy manufacturing routes as well as feed stocks for powder injection molding, and additive manufacturing. Employing atomization processes to achieve spherical powders dates back to 1980s and different attitudes to maintain a plasma current have been developed including gas atomization, plasma atomization, plasma-rotating-electrode atomization, and freefall atomization. Facilities for employing the aforementioned methods have always been expensive. This paper proposes two new processes by which pure spherical powder is achievable with relatively low costs. The first method proposed will deal with attrition of coarse particles in cryogenic milieu via coinciding jets (i.e., cryogenic coinciding jets or CCJ), while the second proposed method concerns melting and evaporation of metals caused by the heat emitted from a plasma channel made by the electric field breakdown at micrometer separations of metallic electrodes (entitled as electrode-plasma-atomization method or EPA). The CCJ method may face challenges such as cold welding of particles due to high speed collision and inefficiency of process because of presence of high plastic deformation and coldworking, whereas the EPA method demands only the use of electrically conductive materials as electrodes. Titanium powder with the particle average sizes of 62nm and also 300-400nm was achieved via the EPA method. Studies also suggest that the CCJ method is expected to produce Titanium nanopowder with less than %0.05wt contamination.