Sonochemistry and bubble dynamics

Abstract

The details of bubble behaviour in chemically active cavitation are still not sufficiently well understood. Here we report on experimental high-speed observations of acoustically driven single-bubble and few-bubble systems with the aim of clarification of the connection of their dynamics with chemical activity. Our experiment realises the sonochemical isomerization reaction of maleic acid to fumaric acid, mediated by bromine radicals, in a bubble trap set-up. The main result is that the reaction product can only be observed in a parameter regime where a small bubble cluster occurs, while a single trapped bubble stays passive. Evaluations of individual bubble dynamics for both cases are given in form of radius-time data and numerical fits to a bubble model. A conclusion is that a sufficiently strong collapse has to be accompanied by non-spherical bubble dynamics for the reaction to occur, and that the reason appears to be an efficient mixing of liquid and gas phase. This finding corroborates previous observations and literature reports on high liquid phase sonochemical activity under distinct parameter conditions than strong sonoluminescence emissions.

Unsteady translation and repetitive jetting of acoustic cavitation bubbles

“…Calculations with a spherical bubble model can reproduce the essentials of the observed motion. Future experiments might establish firm links between the reported translation-induced jetting mode of bubble collapse, the related specific acoustic emission features, and nonvolatile liquid-phase sonochemistry [34].…”

Sonoluminescence and dynamics of cavitation bubble populations in sulfuric acid

“…In addition to translation induced jetting (P-III) or surface mode instabilities (P-II), other liquid injection scenarios might be based on bubble splitting [44] or coalescence [45]. From the observations, extended fragmentation of P-III bubbles during collapse can be excluded apart from the potential ejection of the P-0 trace bubbles, as discussed above.…”

A Novel Synthesis of Zinc Borates from a Zinc Oxide Precursor via Ultrasonic Irradiation

“…As a result, high productivity can be achieved even at low reaction temperatures and shorter reaction times. 15,16 In the literature, several studies can be found on the use of sonochemistry for the preparation of different materials, such as ZnO, 17 22 However, sonochemistry has not been applied for the synthesis of zinc borates. Our group has published two studies on the production of zinc borates via the ultrasonic route.…”