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Chemical Bubble Dynamics and Quantitative Sonochemistry

Colussi, A. J. and Weavers, Linda K. and Hoffmann, Michael R. (1998) Chemical Bubble Dynamics and Quantitative Sonochemistry. Journal of Physical Chemistry A, 102 (35). pp. 6927-6934. ISSN 1089-5639. doi:10.1021/jp980930t.

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We model the collapse of a bubble by taking into account all the energy forms involved (i.e., mechanical, thermal, chemical, and radiative) and compare the calculated radical yields with sonochemical data in H_2O. Water decomposition plays a critical role in the energy balance, but trails equilibrium even in bubbles collapsing at subsonic speeds. Integration of the equation of bubble motion coupled with a full chemical mechanism reveals that (1) terminal gas temperatures and Mach numbers M_L increase in cooler water, (2) Γ_(OH), the number of OH^- radicals produced per unit applied work at maximum M_L when bubbles become unstable and disperse into the liquiddecreases at small and very large sound intensities. We show that available data on the sonochemical decomposition of volatile solutessuch as CCl4, which is pyrolyzed within collapsing bubblesare compatible with the efficient conversion of ultrasonic energy into transient cavitation. On this basis we calculate Γ_(OH) = (1 ± 0.5) × 10^(17) molecules/J for R_0 = 2 μm bubbles optimally sonicated at 300 kHz and 2.3 W/cm^2 by assuming mass and energy accommodation coefficients of α ≤ 7 × 10^(-3) and ε ≤ 0.04, respectively, in gas−liquid collisions, and values about 3-fold smaller after averaging over the nuclei size distribution. Since there is negligible radical recombination during dispersal, these Γ_(OH) values represent available oxidant yields, that agree with experimental data on iodide sonochemical oxidation. Bubbles emit little radiation, suggesting that only radial shock waves may heat small regions to the 10^4 − 10^5 K range required by some sonoluminescence experiments. The contribution of this sonoluminescent core to sonochemical action is, however, insignificant. We show that much larger accommodation coefficients would lead to higher temperatures, but also to O atoms rather than OH radicals and ultimately to excess O_2, at variance with experimental evidence.

Item Type:Article
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URLURL TypeDescription
Colussi, A. J.0000-0002-3400-4101
Hoffmann, Michael R.0000-0001-6495-1946
Additional Information:© 1998 American Chemical Society. Received: January 28, 1998; In Final Form: June 12, 1998. A.J.C. is a visiting scientist, on leave from the University of Buenos Aires and the National Research Council of Argentina. Financial support from Advanced Research Projects Agency, ARPA (Grant NAV5HFMN N0001492J1901), the Office of Naval Research, ONR, the Electric Power Institute, EPRI (Grant RP 8003-37), and the Department of Energy, DOE/Argonne, Grant 1963472402, is gratefully acknowledged. We thank the reviewers for valuable comments.
Funding AgencyGrant Number
Advanced Research Projects Agency (ARPA)NAV5HFMN N0001492J1901
Office of Naval Research (ONR)UNSPECIFIED
Electric Power Research Institute (EPRI)RP 8003-37
Department of Energy (DOE)1963472402
Issue or Number:35
Record Number:CaltechAUTHORS:20150623-154801749
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Official Citation:Chemical Bubble Dynamics and Quantitative Sonochemistry A. J. Colussi, Linda K. Weavers, and Michael R. Hoffmann The Journal of Physical Chemistry A 1998 102 (35), 6927-6934 DOI: 10.1021/jp980930t
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:58498
Deposited By: George Porter
Deposited On:24 Jul 2015 20:32
Last Modified:10 Nov 2021 22:06

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