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DTSTART:20160327T030000
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DTSTART:20161030T020000
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DTSTAMP:20260429T024542Z
UID:57209db7e4d83324450522@ist.ac.at
DTSTART:20161010T160000
DTEND:20161010T171500
DESCRIPTION:Speaker: Kenneth S. Suslick\nAbstract: Fundamentally\, chemistr
 y is the interaction of energy and matter. Surprisingly\, there are relati
 vely few ways of putting energy into molecules. High intensity ultrasound 
 has found numerous applications in driving chemical reactions and in the p
 reparation of unusual materials\, creating the field of sonochemistry. The
  chemical effects of ultrasound originate from acoustic cavitation: the fo
 rmation\, growth\, and implosive collapse of bubbles in a liquid. From son
 oluminescence spectroscopy\, we have established that cavitation produces 
 local conditions inside the bubbles of ~5000 K\, ~1000 atm\, with heating 
 and cooling rates that exceed 1010 K/s. In isolated single bubbles\, which
  can collapse more symmetrically and effectively\, temperatures exceeding 
 20\,000 K are observed.\nIn otherwise cold liquids\, ultrasound is able to
  drive reactions that normally occur only under extreme conditions. The so
 nochemical syntheses of nanostructured metals\, alloys\, metal carbides\, 
 supported heterogeneous catalysts\, and nano-colloids derives from the son
 ochemical decomposition of volatile organometallic precursors during cavit
 ation\, which produces clusters a few nm in diameter. Such nanostructured 
 solids are active heterogeneous catalysts for various reactions. As exampl
 es\, we have discovered a new synthesis of nanostructured MoS2 and Mo2C an
 d of transition metal colloids of iron\, cobalt\, and iron-cobalt alloy co
 lloids. Sonication of molybdenum hexacarbonyl in the presence of sulfur pr
 oduces a novel morphology of MoS2 with extremely high activity for catalyt
 ic hydrodesulfurization.\nAnother remarkable phenomenon occurs during ultr
 asonic irradiation of liquid-solid slurries: extremely high speed inter-pa
 rticle collisions. Turbulent flow and shock waves produced by acoustic cav
 itation can drive metal particles together at sufficiently high velocities
  to induce melting upon collision. Metal particles that are irradiated in 
 hydrocarbon liquids with ultrasound undergo collisions at roughly half the
  speed of sound and generate localized effective temperatures of ~3000 K a
 t the point of impact. As a consequence\, both stoichiometric and catalyti
 c liquid-solid reactions can be tremendously enhanced. In addition\, sonof
 ragmentation of molecular crystals occurs readily\, which greatly improves
  the uniformity of particles formed during crystallization\, for example\,
  of active pharmaceutical ingredients.
LOCATION:Raiffeisen Lecture Hall\, Central Building\, ISTA
ORGANIZER:aeller@ist.ac.at
SUMMARY:Kenneth S. Suslick: The Institute Colloquium: Inside a collapsing b
 ubble: sonochemistry and sonoluminesce
URL:https://talks-calendar.ista.ac.at/events/180
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