Determination of Size Distribution of Condensed Metal Particles

Abstract

A method was developed for measuring the size distribution of particles condensed from metal vapor, at ambient conditions. Particles were collected on a carbon coated surface of mica cleaved along its crystal plane and were shadowed with chromium. The collected samples were photographed through an electron microscope. Size distributions were determined by actual count of the particle images in the photographs after enlargement. The metal vapor was obtained by evaporating metal wires electrically (exploding) at ambient conditions. Primarily platinum wire was used but some zinc and iron were also employed. While the kind of metal and the amount of energy transferred play a role, in all cases it was shown that the particle size distribution is much wider than the distribution of particles from condensation in supersonic nozzles. There appear to be definite limits to the flow fields for which the common assumption that condensed particles are uniform in size is valid.