G. Beaucage
Professor of Chemical and Materials Engineering
University of Cincinnati, OH 45221-0012
Abstract:
Large scale
production of nanoparticles requires conditions far from equilibrium and
dominated by kinetics. Often, seemingly unwieldy and dramatic events such
as explosions and fire can lead to well controlled nanomaterials. Such
synthetic processes were largely discovered through serendipity and, to a
great extent, our understanding of particle formation and growth under such
conditions is limited to Edisonian approaches, although recent advances in
simulation and modeling have enhanced control. The production of
nanostructured carbon, silica, titania and alumina on an industrial scale is
partly based in industrial application of pyrolytic approaches. From the
initial nucleation event to growth, aggregation of particles to
agglomeration of aggregates, direct measurement has been severely hindered
by dilute conditions (10-6 volume fraction), high temperatures
(1000-3000 °C), optical emission, complications due to continuous flow (such
as exhaust) and rapid aggregation and coalescence when nano-droplets are
extracted from a flame. In addition to synthetic flame aerosols,
environmental aerosols, exhaust aerosols (from diesel engines for instance),
CVD byproduct aerosols and interstellar aerosols (interstellar dust) have
made the study of basic physico-chemical processes in these systems of
importance to a wide spectrum of scientists. This talk will describe recent
efforts at understanding the dynamics of nanoparticle formation in a variety
of synthetic aerosols using small-angle x-ray scattering at third generation
synchrotron sources. This work was performed in collaboration with the ETH
group of Pratsinis, with the UNICAT facility at APS, and with T. Narayanan
at ID02/ESRF in Grenoble, France. The work is supported by NSF, Swiss NSF,
and the user facilities.
2008 Run
Nov 19th - Dec 22nd
