Phase and size control of nanometer-size materials synthesized in supersonic jet expansions

We present results of experimental studies to control the phase and size of nanometer-size materials generated in supersonic jet expansions. The effects of expansion conditions such as initial temperature, stagnation pressure, mole fraction of sample in the carrier gas, geometry of the nozzle, and location in the jet have been examined. The experimental results indicate that relatively larger nanometer-size particles may be obtained by using lower starting temperature, higher carrier gas pressure, relatively lower mole fraction up to a point where the release of the heat from condensation is no longer the dominant control factor. Laval nozzles instead of tubular nozzles, and by taking the materials from the central core of the supersonic jet.