Generation of aerosols by the electrical explosion of wires at reduced air pressure

Abstract

The exploding wire method of particle production allows the authors to model the high speed formation of aerosols because of the fast heating and evaporation rates inherent to this technique. The method is also of interest from the viewpoint of controlling the production of aerosols of a particular material with a specific particle size distribution at a specific efficiency. The electrical explosion of iron, aluminum, titanium, and copper wires have been investigated in various gases at pressures from 0.01 to 1 atm. In these experiments the energy density introduced into the material, w, is normalized to the sublimation energy of the material, w{sub s}. The energy density also controls the heating rate. Particle and agglomerate sizes were determined using transmission electron microscopy and laser scattering methods. The specific surface area of the powder was measured by low-temperature adsorption. The phase composition was determined by X-ray diffraction. Increasing the energy density increases the internal energy of the material, the expansion velocity and the number of condensation centers, while the final particle size decreases. With an exothermic oxidation reaction, the optimum energy density can be less than the sublimation energy of the material. As a result, metal oxides are formed. Electrical explosion of wires, at reduced air pressures, allows for the production of ultra-fine powders of oxides of various metals with particle sizes of less than 50 nm. The method is environmentally safe and does not require excess energy expenditures. The electrical explosion of wire at reduced pressure allows for new possibilities in the production of ultra-fine powders (UFP).