Cavitation-induced shock wave behaviour in different liquids

An eco-friendly solution for liquid phase exfoliation of graphite under optimised ultrasonication conditions

“…However, bubbles in DIW:EtOH with a surface tension closer to NMP and higher viscosity produce a stable "mist" of bubbles that has been previously identified in Ref. [32] as a potential mechanism to enhance exfoliation via the interaction with partially exfoliated graphene flakes as predicted in Ref. [14].…”

“…The cavitation strength is directly affected by the surface tension at the liquid-gas interface, as well as the initial bubble radius, therefore, we can also expect the large pressure difference between DIW and EtOH (having the highest and lowest surface tension, respectively). Due to the ability of EtOH to reduce cavitation bubble impact [32], we can hypothesise that a bulk-layered material exposed to repeated SWs (of smaller acoustic pressure, Fig. 2) would suffer lesser deleterious effects such as structural defects.…”

“…Although the analysis on the bubble dynamics in conjunction with synchronised acoustic pressure measurements gave us some indication as to the mechanisms through which sonication in different solvents may affect exfoliation, more specific features of this exfoliation can be analysed through detailed observation of SW generation and propagation for each solvent. Previous research from our group had demonstrated SW analysis from the perspective of acoustic spectra [22,32], however, to gain a better insight shadowgraphic photography was utilised to evaluate the evolution and propagation of SWs in real-time. This was taken as a pre-condition experiment before we undertook ULPE for extended durations (Section 3.2).…”

“…Our group has previously investigated the frequency spectra related to SW generation for DIW [22] and EtOH and DIW:EtOH [32]. The findings for DIW revealed a characteristic pressure peak at ~3.3 MHz predominantly generated via SWs.…”

Effects of Green Solvents and Surfactants on the Characteristics of Few-Layer Graphene Produced by Dual-Frequency Ultrasonic Liquid Phase Exfoliation Technique

“…Prominent peaks apparent in the beginning become then hidden by the enlargement of the cavitation noise. This is expected as the formation of a bubbly mist can absorb shock waves intensity while expanding significantly the cavitation zone [42,48]. In the case of adding ethanol in the WSC the waveform also shows broadening of the cavitation noise due to more bubbles/clouds oscillations but also presents sharp peaks attesting for the SW propagating in the liquid solution.…”