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Kenneth S. Suslick - One of the best experts on this subject based on the ideXlab platform.
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single bubble perturbation in cavitation proximity of solid glass hot spot versus distance
Physical Chemistry Chemical Physics, 2014Co-Authors: Darya Radziuk, Helmuth Mohwald, Kenneth S. SuslickAbstract:A systematic study of the energy loss of a cavitation bubble in a close proximity of a glass surface is introduced for the first time in a low acoustic field (1.2–2.4 bar). Single bubble Sonoluminescence (SBSL) is used as a tool to predict the temperature and pressure decrease of bubble (μm) versus surface distance. A glass as a model system is used to imitate the boundary conditions relevant for nano- or micromaterials. SBSL preequilibrated with 5% argon is perturbed by a glass rod with the tip (Z-perturbation) and with the long axis (X-perturbation) at a defined distance. From 2 mm to 500 μm argon-SBSL lines monotonically narrow and the effective emission temperature decreases from 9000 K to 6800 K comparable to multiple bubbles. The electron density decreases by two orders of magnitude in Z-perturbation and is by a factor of two higher in X-perturbation than the unperturbed cavitating bubble. The perturbed single bubble Sonoluminescence pressure decreases from 2700 atm to 1200 atm at 2.4 bar. In water new non-SBSL SiO molecular emission lines are observed and OH emission disappears.
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temperature nonequilibration during single bubble Sonoluminescence
Journal of Physical Chemistry Letters, 2012Co-Authors: David J. Flannigan, Kenneth S. SuslickAbstract:Single-bubble Sonoluminescence (SBSL) spectra from liquids having low vapor pressures, especially mineral acids, are exceptionally rich. During SBSL from aqueous sulfuric acid containing dissolved neon, rovibronic emission spectra reveal vibrationally hot sulfur monoxide (SO; Tv = 2100 K) that is also rotationally cold (Tr = 290 K). In addition to SO, excited neon atom emission gives an estimated temperature, for neon, of several thousand Kelvin. This nonequilibrated temperature is consistent with dynamically constrained SO formation at the liquid-vapor interface of the collapsing bubble. Formation occurs via collisions of fast neon atoms (generated within the collapsing bubble) with liquid-phase molecular species in the interfacial region, thus allowing for a mechanistic understanding of the processes leading to light emission.
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extreme conditions during multibubble cavitation Sonoluminescence as a spectroscopic probe
Ultrasonics Sonochemistry, 2011Co-Authors: Kenneth S. Suslick, David J. Flannigan, Nathan C Eddingsaas, Stephen D HopkinsAbstract:We review recent work on the use of Sonoluminescence (SL) to probe spectroscopically the conditions created during cavitation, both in clouds of collapsing bubbles (multibubble Sonoluminescence, (MBSL)) and in single bubble events. The effective MBSL temperature can be controlled by the vapor pressure of the liquid or the thermal conductivity of the dissolved gas over a range from ∼1600 to ∼9000K. The effective pressure during MBSL is ∼300bar, based on atomic line shifts. Given nanosecond emission times, this means that cooling rates are >10(12)K/s. In sulfuric and phosphoric acid, the low volatility and high solubility of any sonolysis products make bubble collapse more efficient and evidence for an optically opaque plasma core is found.
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temperature inhomogeneity during multibubble Sonoluminescence
Angewandte Chemie, 2010Co-Authors: Nick Glumac, Kenneth S. SuslickAbstract:When a liquid is subjected to high-intensity ultrasound, bubbles are formed, grow, and implosively collapse. This phenomenon of acoustic cavitation generates both chemical reactions (i.e., sonochemistry) and the emission of light (i.e., Sonoluminescence, SL). It is generally agreed that both sonochemistry and Sonoluminescence result from the intense compressional heating of gas and vapor inside the collapsing bubbles, and the extraordinary temperatures and pressures thus created. The emission of light can occur either from a cloud of cavitating bubbles (i.e., multibubble Sonoluminescence, MBSL), or in a carefully controlled standing wave acoustic field from a single isolated bubble (i.e., single-bubble Sonoluminescence, SBSL). MBSL is more closely related to sonochemistry, and quantification of the conditions generated during MBSL can lead to a better understanding of sonochemistry. Measurement of atomic and molecular emission from volatile species during MBSL revealed effective temperatures of thousands of Kelvins created during bubble collapse. Little is known, however, about the origin of emission derived from nonvolatile species during MBSL. This emission is directly relevant to the observed sonochemistry of dissolved reactants. Extensive emission bands and lines have been observed both from aqueous and non-aqueous liquids during MBSL, and can be used as spectroscopic thermometers to quantify the conditions generated inside the collapsing bubbles. For example, the Swan bands of C2 , [8,14] excited-state metal atoms (e.g., Fe, Cr, Mo), and even excited state Ar emission have been used to measure the intracavity temperatures. Other nonspectroscopic methods have also been used to measure the temperatures of cavitating bubbles. No prior study, however, has reported simultaneous measurement of temperature from two or more independent emitting species, which would permit one to probe the homogeneity of the temperature profile generated in bubble clouds from spatial variance during acoustic cavitation. By examining the MBSL from aqueous H3PO4 solutions, we have observed ultrabright Sonoluminescence, found strong molecular emissions from both OHC and POC radicals, and have succeeded in using both simultaneously as spectroscopic thermometers. There is a dramatic temperature inhomogeneity that is dependent on the location within the bubble cloud and is consistent with two distinct kinds of cavitating bubbles: those that collapse symmetrically and those that do not. H3PO4 is a strongly hydrogen-bonded liquid; it has a relatively high viscosity and low vapor pressure (ca. 2.4 Torr for 85%H3PO4). Interestingly, the vapor of H3PO4 consists of water molecules alone; there are no acid molecules present in the vapor over most concentrated H3PO4 samples, even at high temperatures. Thus, in the gas phase of H3PO4 , the only volatile component inside the bubbles is water vapor; the phosphoric acid molecules can be considered as nonvolatile species during MBSL. Ultrabright Sonoluminescence from 85% H3PO4 saturated with noble gases can be observed by naked eye, even in a well-lit room, as shown in Figure 1.
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evidence for a plasma core during multibubble Sonoluminescence in sulfuric acid
Journal of the American Chemical Society, 2007Co-Authors: Nathan C Eddingsaas, Kenneth S. SuslickAbstract:Multibubble Sonoluminescence arises from the cavitation of bubbles owing to high-intensity ultrasonic irradiation of liquids. The spectrum of multibubble Sonoluminescence in concentrated sulfuric acid sparged with Ar, at relatively low acoustic power, consists of a broad continuum extending into the UV with SO and Ar emission lines on top of this continuum. The observation of the Ar lines indicates that an optically opaque plasma is probably generated inside the bubble during cavitation. There are three distinct light-emitting morphologies for multibubble Sonoluminescence from an ultrasonic horn; as the acoustic intensity is increased, the emission changes from filamentous, to bulbous, to cone shaped, and it is only from the filamentous emission that strong atomic and molecular emissions are observed.
Muthupandian Ashokkumar - One of the best experts on this subject based on the ideXlab platform.
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influence of frequency sweep on sonochemiluminescence and Sonoluminescence
Ultrasonics Sonochemistry, 2020Co-Authors: Loic Hallez, Muthupandian Ashokkumar, Francis Touyeras, Jeanyves HihnAbstract:Abstract Bubbles generated by acoustic cavitation may be efficient in light production by direct emission (Sonoluminescence) or indirect emission (sonochemiluminescence) depending on operating parameters such as acoustic pressure and surface tension. These conditions are quite difficult to reach at very high frequencies, even by concentrating the acoustic power at a given location via focusing the acoustic field thanks to the transducer shape (High Intensity Focused Ultrasound). The current work aims at probing the cavitation bubble behaviour under short frequency sweeps by monitoring sonochemiluminescence and Sonoluminescence activities. When the frequency was swept in reverse (negative sweep), an enhancement in the SCL, relative to the SCL observed under a single frequency irradiation, was observed. Conversely, a positive frequency sweep resulted in the quenching of SCL intensity. The degree of SCL enhancement and quenching was also dependent on the rate at which the frequency was being swept and on the change in the size of cavitation bubbles. The size of cavitation bubbles varied with varying starting sweep frequency (3.4, 3.6 and 4.2 MHz), affecting both SCL and Sonoluminescence (SL) emissions. The addition of a surfactant (sodium dodecyl sulphate) affected the observed results, possibly due to its influence on coalescence between cavitation bubbles. The results suggest that the enhancement and quenching are related to the response of bubbles generated by the starting frequency to the direction of the frequency sweep and the influence of the sweep rate on growth and coalescence of bubbles, which affected the population of the active bubbles.
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Effect of NaCl salt on sonochemistry and Sonoluminescence in aqueous solutions
Ultrasonics Sonochemistry, 2019Co-Authors: Rachel Pflieger, Sergey Nikitenko, Muthupandian AshokkumarAbstract:The presence of salts in a solution is known to affect sonochemistry, but until now no consensus has been reached in the literature on how and why a salt influences sonochemistry. The present study focuses on the effect of NaCl on sonochemical activity and Sonoluminescence at 362-kHz frequency in aqueous solutions saturated with He and Ar. It is shown that the presence of salt has a multiple impact: the global population of active bubbles decreases due to the decreasing gas solubility, new chemical reactions involving Na and Cl atoms occur that influence hydrogen and hydrogen peroxide yields and the standing wave component of the US wave is enhanced, favoring Sonoluminescence emission. Interestingly, the effect of salt greatly depends on the nature of the saturating gas: for instance, strong acidification occurs under He, while it is limited under Ar.
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inverse effects of the gas feed positioning on sonochemistry and Sonoluminescence
Ultrasonics Sonochemistry, 2018Co-Authors: Rachel Pflieger, Muthupandian Ashokkumar, Lea Gravier, Gilles Guillot, Sergey I NikitenkoAbstract:Purging of solutions to enhance sonochemical reactions is a common practice. A fundamental study combining Sonoluminescence spectroscopy and sonochemical activity is adopted to study the effects of continuous Ar gas flow in the solution and of the position of the gas inlet tube on high-frequency sonolysis of aqueous solutions. It has been observed that neither sonochemical activity nor Sonoluminescence intensity is controlled by the gas solubility only. Besides, the change in position of the gas inlet tube leads to opposite effects in Sonoluminescence intensity and sonochemical activity: while the former increases, the latter decreases. Such an observation has never been reported despite sonochemical reactions have been carried out under different gas environments. Sonoluminescence spectroscopy indicates that more extreme conditions are reached at collapse with the gas inlet on the side, which could be explained by a more symmetrical collapse. Finally, it is shown in certain conditions that it is possible to favor the formation of some sonochemical products simply by positioning the gas inlet at different positions, which has practical significance in designing large scale sonochemical reactors for industrial applications.
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quantification of cavitation activity by Sonoluminescence to study the sonocrystallization process under different ultrasound parameters
Crystal Growth & Design, 2018Co-Authors: Kyuichi Yasui, Judy Lee, Muthupandian Ashokkumar, Sandra E KentishAbstract:In this study, both the antisolvent sonocrystallization process of sodium chloride and cavitation activity were investigated as a function of frequency (22–1080 kHz) and acoustic calorimetric power (0–30 W). For frequencies between 20 and 139 kHz, the size of the sodium chloride crystals decreased sharply with increasing power. For frequencies 647 and 1080 kHz, a certain power threshold needs to be exceeded before a decrease in the crystal size was observed. This power threshold coincided with the power threshold for Sonoluminescence emission from cavitation bubbles. It was found that the onset of cavitation bubble activity, irrespective of the magnitude (measured in terms of Sonoluminescence), enhanced the crystal nucleation rate and decreased crystal size. The minimum crystal size obtained was found to decrease with increasing maximum total integrated Sonoluminescence intensity. The results suggest Sonoluminescence could be used as a measure to evaluate the sonocrystallization process and that a greater...
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initial growth of sonochemically active and Sonoluminescence bubbles at various frequencies
Ultrasonics Sonochemistry, 2016Co-Authors: Bandar A Babgi, Muthupandian Ashokkumar, Meifang Zhou, Mecit Aksu, Yousef G AlghamdiAbstract:The initial growth of acoustic cavitation activity is important in some applications such as therapeutic and diagnostic medicine. The initial growth of cavitation activity has been investigated using Sonoluminescence and sonochemical activity (sonochemiluminescence) at 358 kHz, 647 kHz and 1062 kHz and at 5 W, 15 W and 30 W applied power levels. The growth of sonochemically active bubble population is found to be much faster than that of Sonoluminescence bubble population at 358 kHz and 647 kHz whereas almost similar growth rate is observed at 1062 kHz for both bubble populations. This suggests that the cavitation bubble resonance size ranges of Sonoluminescence and sonochemically active bubbles are different at 358 kHz and 647 kHz, whereas they have similar size range at 1062 kHz. At 358 kHz and 647 kHz, relatively smaller bubbles become chemically active. Possible reasons for such observations have been discussed. The data presented and discussed in this study may be useful in controlling the growth of cavitation bubble population in addition to enhancing the knowledge base in cavitation science.
Seth Putterman - One of the best experts on this subject based on the ideXlab platform.
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blackbody emission from laser breakdown in high pressure gases
Physical Review Letters, 2014Co-Authors: A Bataller, Brian Alan Kappus, G R Plateau, Seth PuttermanAbstract:: Laser induced breakdown of pressurized gases is used to generate plasmas under conditions where the atomic density and temperature are similar to those found in sonoluminescing bubbles. Calibrated streak spectroscopy reveals that a blackbody persists well after the exciting femtosecond laser pulse has turned off. Deviation from Saha's equation of state and an accompanying large reduction in ionization potential are observed at unexpectedly low atomic densities-in parallel with Sonoluminescence. In laser breakdown, energy input proceeds via excitation of electrons whereas in Sonoluminescence it is initiated via the atoms. The similar responses indicate that these systems are revealing the thermodynamics and transport of a strongly coupled plasma.
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energy balance for a Sonoluminescence bubble yields a measure of ionization potential lowering
Physical Review Letters, 2013Co-Authors: Brian Alan Kappus, Alexander Bataller, Seth PuttermanAbstract:Application of energy conservation between input sound and the microplasma which forms at the moment of Sonoluminescence places bounds on the process, whereby the gas is ionized. Detailed pulsed Mie scattering measurements of the radius versus time for a xenon bubble in sulfuric acid provide a complete characterization of the hydrodynamics and minimum radius. For a range of emission intensities, the blackbody spectrum emitted during collapse matches the minimum bubble radius, implying opaque conditions are attained. This requires a degree of ionization >36%. Analysis reveals only 2.1±0.6 eV/atom of energy available during light emission. In order to unbind enough charge, collective processes must therefore reduce the ionization potential by at least 75%. We interpret this as evidence that a phase transition to a highly ionized plasma is occurring during Sonoluminescence.
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opacity and transport measurements reveal that dilute plasma models of Sonoluminescence are not valid
Physical Review Letters, 2012Co-Authors: Shahzad Khalid, Keith Weninger, Brian Alan Kappus, Seth PuttermanAbstract:A strong interaction between a nanosecond laser and a 70 μm radius sonoluminescing plasma is achieved. The overall response of the system results in a factor of 2 increase in temperature as determined by its spectrum. Images of the interaction reveal that light energy is absorbed and trapped in a region smaller than the Sonoluminescence emitting region of the bubble for over 100 ns. We interpret this opacity and transport measurement as demonstrating that sonoluminescencing bubbles can be 1000 times more opaque than what follows from the Saha equation of statistical mechanics in the ideal plasma limit. To address this discrepancy, we suggest that the effects of strong Coulomb interactions are an essential component of a first principles theory of Sonoluminescence.
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Sonoluminescence from a single bubble driven at 1 megahertz
Physical Review Letters, 2004Co-Authors: Carlos G Camara, Seth Putterman, Emil KirilovAbstract:Measurements of the spectrum of Sonoluminescence from an isolated bubble driven at 1 MHz are well fit by assuming thermal bremsstrahlung from a transparent 10(6) degree plasma. According to this interpretation, the photon-matter mean free path is larger than the light-emitting radius of a 1 MHz bubble, but smaller than the light-emitting radius for bubbles driven at approximately 40 kHz, thus accounting for the observed blackbody spectrum at 40 kHz.
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Sonoluminescence nature s smallest blackbody
Optics Letters, 2001Co-Authors: G Vazquez, Seth Putterman, Carlos G Camara, Keith WeningerAbstract:The transduction of sound into light through the implosion of a bubble of gas leads to a flash of light whose duration is delineated in picoseconds. Combined measurements of spectral irradiance, Mie scattering, and flash width (as determined by time-correlated single-photon counting) suggest that Sonoluminescence from hydrogen and noble-gas bubbles is radiation from a blackbody with temperatures ranging from 6000 KH2 to 20,000 K (He) and a surface of emission whose radius ranges from 0.1 μmHe to 0.4 μmXe. The state of matter that would admit photon–matter equilibrium under such conditions is a mystery.
Sergey I Nikitenko - One of the best experts on this subject based on the ideXlab platform.
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inverse effects of the gas feed positioning on sonochemistry and Sonoluminescence
Ultrasonics Sonochemistry, 2018Co-Authors: Rachel Pflieger, Muthupandian Ashokkumar, Lea Gravier, Gilles Guillot, Sergey I NikitenkoAbstract:Purging of solutions to enhance sonochemical reactions is a common practice. A fundamental study combining Sonoluminescence spectroscopy and sonochemical activity is adopted to study the effects of continuous Ar gas flow in the solution and of the position of the gas inlet tube on high-frequency sonolysis of aqueous solutions. It has been observed that neither sonochemical activity nor Sonoluminescence intensity is controlled by the gas solubility only. Besides, the change in position of the gas inlet tube leads to opposite effects in Sonoluminescence intensity and sonochemical activity: while the former increases, the latter decreases. Such an observation has never been reported despite sonochemical reactions have been carried out under different gas environments. Sonoluminescence spectroscopy indicates that more extreme conditions are reached at collapse with the gas inlet on the side, which could be explained by a more symmetrical collapse. Finally, it is shown in certain conditions that it is possible to favor the formation of some sonochemical products simply by positioning the gas inlet at different positions, which has practical significance in designing large scale sonochemical reactors for industrial applications.
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multibubble sonochemistry and Sonoluminescence at 100 khz the missing link between low and high frequency ultrasound
Journal of Physical Chemistry B, 2018Co-Authors: Rachel Pflieger, Matthieu Virot, Sergey I NikitenkoAbstract:Ultrasonic frequency is one of the most important parameters that decides the characteristics of acoustic cavitation. Low- (16–50 kHz) and high- (≥200 kHz) frequency ultrasounds present opposite physical and chemical behaviors and have been extensively studied, yet frequencies in between are poorly characterized. In this study, acoustic cavitation at the intermediate ultrasonic frequency of 100 kHz is compared with that at 20 kHz and at 362 kHz by different experimental investigations: sonochemical yield (H2O2), images of sonochemiluminescence and Sonoluminescence, as well as Sonoluminescence spectra in aqueous media saturated with Ar or Ar/(20 vol %)O2. The chemical activity (H2O2 yield) of cavitation bubbles at 100 kHz presents a transitional behavior between low and high frequencies. The active cavitation zone distributes in the whole sonicated volume, similarly to high-frequency ultrasound and much further than at 20 kHz. The spectral shape of 100 kHz spectra is similar to that at 20 kHz. On the contr...
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spectroscopy of Sonoluminescence and sonochemistry in water saturated with n2 ar mixtures
Journal of Physical Chemistry B, 2015Co-Authors: Temim Ouerhani, Rachel Pflieger, Warda Ben Messaoud, Sergey I NikitenkoAbstract:Sonoluminescence spectra in relation with sonochemical activity of water sparged with Ar/N2 gas mixtures were systematically studied at two ultrasonic frequencies (20 and 359 kHz). At 20 kHz, solely the molecular emission of OH (A2Σ+–X2Πi) is observed in addition to a broad continuum typical for multibubble Sonoluminescence. On the contrary, at high frequency a second emission band is present around 336 nm which is assigned to the NH (A3Π–X3Σ–) system. In addition, the sonolysis of a 0.2 M NH3·H2O solution at 359 kHz in the presence of pure Ar yields the emission bands of NH (A3Π – X3Σ–) (336 nm) and NH (C1Π–A1Δ) (322 nm) systems confirming the sonochemical production of NH radicals. The N2 (C3Πu–B3Πg) emission band is absent at both frequencies. This uncommon phenomenon can be explained by the quenching of the N2 (C3Πu) excited state with water molecules inside the bubbles. The Sonoluminescence of NH radicals at 359 kHz indicates more effective intrabubble dissociation of N2 molecules at high ultrasonic ...
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spectroscopy of Sonoluminescence and sonochemistry in water saturated with n2 ar mixtures
Journal of Physical Chemistry B, 2015Co-Authors: Temim Ouerhani, Rachel Pflieger, Warda Ben Messaoud, Sergey I NikitenkoAbstract:Sonoluminescence spectra in relation with sonochemical activity of water sparged with Ar/N2 gas mixtures were systematically studied at two ultrasonic frequencies (20 and 359 kHz). At 20 kHz, solely the molecular emission of OH (A(2)Σ(+)-X(2)Πi) is observed in addition to a broad continuum typical for multibubble Sonoluminescence. On the contrary, at high frequency a second emission band is present around 336 nm which is assigned to the NH (A(3)Π-X(3)Σ(-)) system. In addition, the sonolysis of a 0.2 M NH3·H2O solution at 359 kHz in the presence of pure Ar yields the emission bands of NH (A(3)Π - X(3)Σ(-)) (336 nm) and NH (C(1)Π-A(1)Δ) (322 nm) systems confirming the sonochemical production of NH radicals. The N2 (C(3)Πu-B(3)Πg) emission band is absent at both frequencies. This uncommon phenomenon can be explained by the quenching of the N2 (C(3)Πu) excited state with water molecules inside the bubbles. The Sonoluminescence of NH radicals at 359 kHz indicates more effective intrabubble dissociation of N2 molecules at high ultrasonic frequency compared to low-frequency (20 kHz) ultrasound. Its absence at 20 kHz may also be related to strong quenching, e.g., by water molecules. The kinetic study of the formation of principal sonochemical products (H2, H2O2, HNO3, HNO2) confirmed the more drastic conditions produced during bubble collapse at higher ultrasonic frequency.
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The origin of isotope effects in Sonoluminescence spectra of heavy and light water
Angewandte Chemie - International Edition, 2013Co-Authors: Abdoul Aziz Ndiaye, Bertrand Siboulet, Rachel Pflieger, Sergey I NikitenkoAbstract:Bubble and peak: The isotope effects in the Sonoluminescence spectra of light and heavy water under ultrasound indicate the formation of a non-equilibrium plasma inside the collapsing cavitation bubbles. The picture demonstrates the active cavitation zones in water at 204 kHz.
Franz Grieser - One of the best experts on this subject based on the ideXlab platform.
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effect of power and frequency on bubble size distributions in acoustic cavitation
Physical Review Letters, 2009Co-Authors: Adam Brotchie, Franz Grieser, Muthupandian AshokkumarAbstract:Acoustic bubble-size distributions have been determined using a pulsed ultrasound method at different ultrasound powers and frequencies. It was observed that the mean bubble size increased with increasing acoustic power and decreased with increasing ultrasound frequency. It was also recognized that the mean size of bubbles emitting Sonoluminescence was greater than those producing sonochemiluminescence indicating that the two processes take place in different populations of cavitation bubbles in the system.
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sonochemistry and Sonoluminescence under dual frequency ultrasound irradiation in the presence of water soluble solutes
Journal of Physical Chemistry C, 2008Co-Authors: Adam Brotchie, Franz Grieser, Muthupandian AshokkumarAbstract:The Sonoluminescence emission and sonochemical efficiency of a typical laboratory scale, high-frequency standing wave reactor (355 kHz), stimulated by low-frequency pulses (20 kHz) has been investigated in the presence and absence of some water-soluble solutes, namely, propanol and polyethylene oxide. It has been found that, although dual-frequency sonication causes a decrease in the integrated Sonoluminescence intensity and sonochemical efficiency in water, in the presence of solutes, a significant enhancement in activity could be attained. This enhancement effect is ascribed, in part, to changes in the extent of bubble coalescence brought about by the water-soluble solutes.
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experimental and theoretical investigations on Sonoluminescence under dual frequency conditions
Ultrasonics Sonochemistry, 2008Co-Authors: Parag M Kanthale, Muthupandian Ashokkumar, Adam Brotchie, Franz GrieserAbstract:The multibubble Sonoluminescence (MBSL) intensities from water exposed to the simultaneous ultrasonic irradiation from 20 kHz (fixed at 6.3 W) and 355 kHz (variable power) ultrasound sources have been compared to the MBSL from the individual ultrasound sources under the same power conditions. A synergistic enhancement of the Sonoluminescence (SL) signal, >30-fold, at low powers (4.6 W) of the higher frequency was observed. At a higher acoustic power level (15.8 W) the dual frequency operation produced a decrease in the SL signal. These results are in agreement with previously reported data [P. Ciuti, N.V. Dezhkunov, A. Francescutto, F. Calligaris, F. Sturman, Ultrasonics Sonochem. 10 (2003) 337; N.V. Dezhkunov, J. Eng. Phys. Therm. 76 (2003) 142] under similar experimental conditions. Numerical single bubble (SB) dynamics calculations have been used to help interpret the experimental results. It is suggested that the observed effects are caused by a combination of changes to the peak collapse temperature of individual bubbles as well as to changes in the active bubble population.
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determination of the size distribution of Sonoluminescence bubbles in a pulsed acoustic field
Journal of the American Chemical Society, 2005Co-Authors: Muthupandian Ashokkumar, Sandra E Kentish, Franz GrieserAbstract:A simple method is described for determining the size of Sonoluminescence bubbles generated by acoustic cavitation. The change in the intensity of Sonoluminescence, from 4 ms pulses of 515 kHz ultrasound, as a function of the “off” time between acoustic pulses, is the basis of the method. The bubble size determined in water was in the range of 2.8−3.7 μm.
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a comparison between multibubble Sonoluminescence intensity and the temperature within cavitation bubbles
Journal of the American Chemical Society, 2005Co-Authors: Muthupandian Ashokkumar, Franz GrieserAbstract:Cavitation bubble temperatures have been measured using a methyl radical recombination method and compared with the changes in the Sonoluminescence intensity in aqueous ethanol solutions over a range of concentrations. Whereas the Sonoluminescence intensity was decreased by more than 90% at low ethanol concentrations (<0.1 M), the measured bubble temperatures seem to be unaffected at this level of additive. The cavitation bubble temperatures were noticeably decreased at substantially higher ethanol concentrations (0.5 M). It has been concluded that the methyl radical recombination method does not report on the true Sonoluminescence temperatures. However, it does report on the average bubble temperatures at which sonochemical reactions occur.
