Acoustic cavitation at low gas pressures in PZT-based ultrasonic systems

Joydip Mondal; Wu Li; Amgad R Rezk; Leslie Y Yeo; Rajaram Lakkaraju; Parthasarathi Ghosh; Muthupandian Ashokkumar

doi:10.1016/j.ultsonch.2021.105493

Acoustic cavitation at low gas pressures in PZT-based ultrasonic systems

Ultrason Sonochem. 2021 May:73:105493. doi: 10.1016/j.ultsonch.2021.105493. Epub 2021 Feb 10.

Authors

Joydip Mondal¹, Wu Li², Amgad R Rezk³, Leslie Y Yeo³, Rajaram Lakkaraju⁴, Parthasarathi Ghosh⁵, Muthupandian Ashokkumar⁶

Affiliations

¹ School of Chemistry, The University of Melbourne, VIC 3010, Australia; Cryogenic Engineering Centre, IIT Kharagpur, Kharagpur 721302, India.
² School of Chemistry, The University of Melbourne, VIC 3010, Australia.
³ Micro/Nanophysics Research Laboratory, School of Engineering, RMIT University, Melbourne, VIC 3000, Australia.
⁴ Department of Mechanical Engineering, IIT Kharagpur, Kharagpur 721302, India.
⁵ Cryogenic Engineering Centre, IIT Kharagpur, Kharagpur 721302, India. Electronic address: psghosh@hijli.iitkgp.ernet.in.
⁶ School of Chemistry, The University of Melbourne, VIC 3010, Australia. Electronic address: masho@unimelb.edu.au.

Abstract

The generation of cavitation-free radicals through evanescent electric field and bulk-streaming was reported when micro-volumes of a liquid were subjected to 10 MHz surface acoustic waves (SAW) on a piezoelectric substrate [Rezk et al., J. Phys. Chem. Lett. 2020, 11, 4655-4661; Rezk et al., Adv. Sci. 2021, 8, 2001983]. In the current study, we have tested a similar hypothesis with PZT-based ultrasonic units (760 kHz and 2 MHz) with varying dissolved gas concentrations, by sonochemiluminescence measurement and iodide dosimetry, to correlate radical generation with dissolved gas concentrations. The dissolved gas concentration was adjusted by controlling the over-head gas pressure. Our study reveals that there is a strong correlation between sonochemical activity and dissolved gas concentration, with negligible sonochemical activity at near-vacuum conditions. We therefore conclude that radical generation is dominated by acoustic cavitation in conventional PZT-based ultrasonic reactors, regardless of the excitation frequency.

Keywords: Acoustic cavitation; Cavitation bubbles; Cavitation-free radical generation; Sonochemical activity.