Mar 2022
Abstract:
Sound waves can interact with microbubbles in a liquid. Normally this process is chemically uneventful, however, if the bubbles reach a certain critical size they rapidly collapse, producing local temperatures of as high as 5000 °C, and local pressures of >100 atm. This phenomenon of ultrasound induced growth and collapse of microbubbles in liquids, commonly referred to as acoustic cavitation, leads to light emission (sonoluminescence) and chemical reactions (sonochemistry). Acoustic cavitation also generates strong physical forces that have been found useful in various applications [1].
One of the major hurdles in developing sonochemistry/sonoprocessing for industrial scale applications is the lack of fundamental understanding of how sonochemical reaction efficiency and sonophysical effects are affected by several experimental parameters. For example, the homogeneous distribution of the cavitation zone in a reactor could be achieved by choosing appropriate experimental conditions [2] (Figure 1).
The presentation will cover some fundamental aspects of acoustic cavitation that are relevant to sonochemical and sonoprocessing applications. Key applications of sonochemistry and sonoprocessing, such as synthesis of biofunctional materials and food processing will be discussed.
Figure 1: The left photograph shows the reactor with a ruler to indicate the height of the liquid. A 440 kHz transducer is attached to the bottom of the reactor. Active cavitation zone in open (middle) and closed (right) systems. The photographs show sonoluminescence from the active cavitation zone. It can be seen that the cavitation field is uniformly distributed in a closed system [2].
References
[1] Handbook on Ultrasonics and Sonochemistry, Chief Editor: M. Ashokkumar; Section Editors: S. Anandan, F. Cavalieri, K. Okitsu, K. Yasui, B. Zisu and F. Chemat, Springer (ISBN 978-981-287-279-1), 2016.
[2] M. Ashokkumar, J. Lee, Y. Iida, K. Yasui, T. Kozuka, T. Tuziuti and A. Towata, Spatial distribution of acoustic cavitation bubbles at different ultrasound frequencies, ChemPhysChem, 11, 1680-1684, 2010.
Bio:
Professor Muthupandian Ashokkumar (Ashok) is a Physical Chemist who specializes in Sonochemistry, teaches undergraduate and postgraduate Chemistry and is a senior academic staff member of the School of Chemistry, University of Melbourne. He is currently the Assistant Deputy Vice-Chancellor International at the University of Melbourne. Ashok is a renowned sonochemist, with about 25 years of experience in this field, and has developed a number of novel techniques to characterize acoustic cavitation bubbles and has made major contributions of applied sonochemistry to the Materials, Food and Dairy industry. His research team has developed a novel ultrasonic processing technology for improving the functional properties of dairy ingredients. Recent research also involves the ultrasonic synthesis of functional nano- and biomaterials that can be used in energy production, environmental remediation and diagnostic and therapeutic medicine. He has received about $ 15 million research grants to support his research work that includes several industry projects. He is the Editor-in-Chief of Ultrasonics Sonochemistry, an international journal devoted to sonochemistry research with a Journal Impact Factor of 7.491). He has edited/co-edited several books and special issues for journals; published ~470 refereed papers (H-Index: 70) in high impact international journals and books; and delivered over 200 invited/keynote/plenary lectures at international conferences and academic institutions. Research Group Website: http://sono.chemistry.unimelb.edu.au/
Registration link to join the seminar:
https://kaust.zoom.us/webinar/register/WN_mxGB1dg5QF6rOlreJF90aA