Aerosol synthesis of nanoscale clusters using atmospheric arc evaporation

A gas aggregation source that operates at atmospheric pressure and is capable of producing grams per hour of unaggregated, equiaxed metal clusters with diameters in the nanometer range is described. A controlled current d.c. arc is employed to evaporate metal atoms from a liquid metal pool. These evaporated atoms are entrained in a flowing stream of inert gas and quickly transferred to a quench region where the hot stream from the arc plasma is mixed with a second quench stream of cold inert gas. The quench gas provides rapid cooling and immediate dilution, both initiating cluster growth and suppressing cluster aggregation. Cluster size is controlled by varying the metal atom density and residence time in the arc plasma, in the quench region and in the flow downstream from the quench region.