SYNTHESIS OF NANOSTRUCTURED POWDERS IN AN AEROSOL FLOW CONDENSER

The inert gas-condensation method (ISC) that has been routinely used f or production of nanostructured powders has a number of experimental l imitations, especially in scale-up. To overcome these difficulties an aerosol how condenser (AFC) was constructed and its characteristics an d performance were determined. The structure, morphology and the prima ry particle-size distribution of palladium powders produced under vari ous gas flow conditions were investigated by transmission electron mic roscopy. The size of the Pd particles were found to be log-normally di stributed with median diameters of primary particles between 2.52 and 10.6 nm and geometric standard deviations (GSD) between 1.48 and 1.89. Compared with IGC, the AFC process results in an 80% reduction in the primary particle median diameter and a 17% reduction in the GSD. The primary particle median diameter and the GSD were found to be strongly dependent on the prevalent flow conditions. (C) 1997 Elsevier Science Ltd. All rights reserved.