ABSTRACT
The condensation of metal vapours by diffusion into the cooling medium (usually an inert gas) has been studied in [1] to develop the so-called gas-phase method for producing ultrafine powders. Unlike some isobaric processes, this section deals with the condensation of metal vapour with the rapid expansion into the vacuum. The advantage of this process relative to the isobaric process is the possibility of achieving, at adiabatic expansion, cooling rates of the vapour of the order of 10-7 K/s supersaturated by several orders of magnitude, by spontaneous nucleation in the pure vapour medium and produce a dispersed system as a stream of diluted metal vapour containing solid or liquid particles of the metal. In this experiment we can produce metal particles with the size of an atom to a few microns. And because no foreign environment is involved here, the particles obtained are of particular interest. Condensation in a vacuum eliminates the ingress of impurity particles into the volume and adsorption of impurities on their surface. Such particles should show special physical and chemical activity. The physical activity of these particles can be used for practical purposes, such as for producing thin-film coatings of high quality – the so-called cluster deposition, chemical reactivity, for directional changes in their chemical composition in the process of producing the particles.
