This project is a combined experimental and modelling study of nucleation and growth of fine powders in thermal plasma reactors. The modelling will include such phenomena as reactor chemistry, particle growth by condensation, particle growth by coagulation, and reactor nonuniformities. It should result in a computer code coupling the thermal hydraulics in a RF plasma reactor to these aerosol processes. The model will be guided and tested by an experimental program in which size distributions of the particles are measured for several species of technical importance as functions of flow rate, concentration, and power input. Thermal plasma reactors are attractive candidates for the production of fine powders to be used in ceramics, metallic alloys, and high temperature superconductors. This research should help design such reactors to control particle size, composition, and morphology.