Mechanisms of ultrasonic de-agglomeration of oxides through in-situ high-speed observations and acoustic measurements

Priyadarshi, A., Khavari, M., Subroto, T., Prentice, P. , Pericleous, K., Eskin, D., Durodola, J. and Tzanakis, I. (2021) Mechanisms of ultrasonic de-agglomeration of oxides through in-situ high-speed observations and acoustic measurements. Ultrasonics Sonochemistry, 79, 105792. (doi: 10.1016/j.ultsonch.2021.105792) (PMID:34666238) (PMCID:PMC8524947)

Abstract

Ultrasonic de-agglomeration and dispersion of oxides is important for a range of applications. In particular, in liquid metal, this is one of the ways to produce metal-matrix composites reinforced with micron and nano sized particles. The associated mechanism through which the de-agglomeration occurs has, however, only been conceptualized theoretically and not yet been validated with experimental observations. In this paper, the influence of ultrasonic cavitation on SiO2 and MgO agglomerates (commonly found in lightweight alloys as reinforcements) with individual particle sizes ranging between 0.5 and 10 μm was observed for the first time in-situ using high-speed imaging. Owing to the opacity of liquid metals, a de-agglomeration imaging experiment was carried out in de-ionised water with sequences captured at frame rates up to 50 kfps. In-situ observations were further accompanied by synchronised acoustic measurements using an advanced calibrated cavitometer, to reveal the effect of pressure amplitude arising from oscillating microbubbles on oxide de-agglomeration. Results showed that ultrasound-induced microbubble clusters pulsating chaotically, were predominantly responsible for the breakage and dispersion of oxide agglomerates. Such oscillating cavitation clusters were seen to capture the floating agglomerates resulting in their immediate disintegration. De-agglomeration of oxides occurred from both the surface and within the bulk of the aggregate. Microbubble clusters oscillating with associated emission frequencies at the subharmonic, 1st harmonic and low order ultra-harmonics of the driving frequency were deemed responsible for the breakage of the agglomerates.

• Item Type: Articles
• Additional Information: The authors are sincerely thankful to the UK Engineering and Physical Sciences Research Council (EPSRC) for the financial support received from the UltraMelt2 project (grant EP/R011044/1, EP/R011095/1 and EP/R011001/1).
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Prentice, Dr Paul
• Authors: Priyadarshi, A., Khavari, M., Subroto, T., Prentice, P., Pericleous, K., Eskin, D., Durodola, J., and Tzanakis, I.
• College/School: College of Science and Engineering > School of Engineering > Systems Power and Energy
• Journal Name: Ultrasonics Sonochemistry
• Publisher: Elsevier
• ISSN: 1350-4177
• ISSN (Online): 1873-2828
• Published Online: 15 October 2021
• Copyright Holders: Copyright © 2021 The Authors
• First Published: First published in Ultrasonics Sonochemistry 79: 105792
• Publisher Policy: Reproduced under a Creative Commons License