Initial Studies of Condensing Metal Vapors Carried by Expanding Inert Gases

摘要

A report is presented on the progress of an experimental investigation of the condensation of metal vapors carried by an expanding inert gas initially at high pressure. Three zinc-in-helium tests in the Hotshot tunnel have indicated that the metallic condensate occurs in the form of very small particles; most particles were found to have diameters of from 0.01 to 0.1 microns. These particles were collected on impact probes from the hypersonic nozzle flow and analysed by electronmicroscopy. A spectrographic analysis of the particle samples showed that roughly one percent by mass of contaminants (principally copper, iron and silicon) were added to the zinc in the hotshot arc chamber. In addition to direct particle sampling, the techniques of light scattering and photomicrography (direct photography of the condensed particles) were investigated. The study of light scattering progressed to a bench set-up evaluation and calibration of a system that measures light attenuation by the scattering medium. Although indicating the possibility of the photography of one micron diameter particles traveling at high speed, the study of the photomicrography technique was discontinued in view of the very small particle sizes indicated by the direct samples from the zinc-in-helium tests. (Author)