W0286

Kinetic control of particle growth is needed to produce nano-scale structure. Flame synthesis is an example of such kinetically dominated growth. Nano-particulate metal oxides and carbon are commercially produced in such controlled flames. Fumed silica, pyrolytic titania, alumina, zirconia and mixed oxides as well as carbon black are currently produced by Edisonian approaches that lead to thousands of tons per year of nanoscale powders in the US. The growth process for such nano-particles in flames is also of general interest to a wide range of scientists and engineers such as conbustion scientists who design diesel engines. We have recently performed the first successful in situ measurements of ceramic nano-particle growth in flames using synchrotron radiation at the Advanced Photon Source in Chicago in collaboration with UNICAT scientists and with workers at HBBL ID02 ESRF and at ETH Zurich. The high brilliance of third generation x-ray sources makes possible direct measurement on controlled flames even though the concentration of nano-particles in such a flame is vanishingly small. We were able to map the nucleation event, growth of primary particles as well as formation and growth of ramified aggregates of silica as a function of 3-d position in the flame in these studies. Mappings with 1mm resolution for a 200x50mm area were conducted. These direct observations disagree with several predictions of computer simulations for particle growth in flames and the measurements may lead to rethinking of our basic understanding of flames.