Abstract (Invited) |
The Chemical Consequences of Cavitation
K.S.Suslick (School of Chemical
Sciences, University of Illinois at Urbana-Champaign, Urbana, IL, USA)
e-mail:
ksuslick@uiuc.edu
Fundamentally,
chemistry is the interaction of energy and matter. Surprisingly, there are relatively few ways
of putting energy into molecules. High intensity ultrasound has found new
applications in driving chemical reactions and in the preparation of unusual
materials. The chemical effects of
ultrasound originate from acoustic cavitation:
the formation, growth, and implosive collapse of bubbles in a liquid. From sonoluminescence spectroscopy, we have
established that cavitation produces local conditions inside the bubbles of
about 5000 K and 1000 atmospheres, but on a nanosecond timescale. In otherwise cold liquids, ultrasound is able
to drive reactions that normally occur only under extreme conditions. The sonochemical syntheses of nanostructured
metals, alloys, metal carbides, supported heterogeneous catalysts, and
nano-colloids derives from the sonochemical decomposition of volatile
organometallic precursors during cavitation, which produces clusters a few nm
in diameter. Such nanostructured solids
are active heterogeneous catalysts for various reactions. Even single cavitating bubbles drive
sonochemical reactions, which limits the extent of heating due to
compression. Quantitative confirmation
of the reactions of N2 and O2 in single bubble sonoluminescence in water has
been recently achieved.
Section
: 11