Formation of Ultrafine Metal Particles by Gas Evaporation Technique. I. Aluminium in Helium

Abstract

The appearance of smoke was studied by a video tape recorder. A typical smoke consisted of inner zone, inner front, outer zone and outer front. Smoke particles collected at different parts were studied by electron microscopy. They were large and often showed clear-cut habits in the inner front, while they were small and uniform in the inner and outer zones. The particle size varied with the gas pressure, evaporation temperature and position of collecting particles. The particles grow remarkably by coalescence where no metal vapour exists. All the experimental results on the size can be explained with an empirical rule that particles become larger when the nucleation starts in vapour of higher density.