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Supercritical fluids (or dense gases) have been established as suitable solvents for many nonvolatile or thermally labile compounds. Therapid (< 1CT5 s) solute condensation occurringduring the expansion of a supercritical fluid solution through a nozzle results from solute nucleation and particle growth processes which may be impacted by a variety of experimental parameters. The qualitative effects of solute concentration and of the presence of electrolytes on the physical characteristics of material formed during this process have been explored. The technique is shownto be applicable to both inorganic (Si02) and organic materials (polymers) using a range of supercritical solvents and thus has potential for a variety of applications involving the formation of powders, thin films, and fibers. It is shown that an intimately mixed powder of two inorganic materials (Si02 and KI) or an inorganic and organic combination (KI …