SUMMARY CTS-9730535 Exploratory Study on Low Temperature Synthesis of Nanostructured Particles By a Novel Aero-Sol-Gel Process G. Beaucage, Asst. Professor of Materials Science and Engineering, PI S.E. Pratsinis, Professor of Chemical Engineering, Co-PI University of Cincinnati, Cincinnati, OH 45221-0012 The goal of this project is to investigate the feasibility of novel, room temperature process for synthesis of nanoparticles by carrying our sol-gel reactions in the aerosol phase. A first experimental base will be created with silica and titania nanoparticles. Preliminary experiments have resulted in pure silica nanoparticles (by mass spectroscopy) with specific surface areas comparable to aerogels. These analyses show primary particles smaller than 1.5 nm in diameter aggregated into classical diffusion-limited-aggregates of approximately 30nm with a mass fractal dimension close to 2.5. Such aggregates have long been sought in the hope of developing catalysis supports with the maximum possible surface area. Conventional pyrolytic methods (e.g. flame reactors) are not capable of such morphologies since the primary particles are about an order of magnitude larger. The proposed process involves an exceedingly simple and cost effective approach which borrows from both sol-gel chemistry and laminar flow, pyrolytic (flame) aerosol techniques. In preliminary experiments, sol-gel precursors such as tetraethoxysilane (TEOS) along with other reactants are dispersed in the gas phase in a closely controllled mode using a flow chamber similar to those encountered in flame reactors. Here, however, there is no flame and the entire apparatus is constructed form PVC plastic tubing, rather than quartz of alloys, costing only about $100. In spite of the simplicity of the initial set-up, some degree of control has already been achieved on the nanoscale by variation of the precursor concentration, type and flow rates.
