Ice crystallization in supercooled water has been initiated by focused Nd:YAG laser pulses at 1064 nm wavelength. The pulses of 8 ns duration and up to 2 mJ energy produce a bubble in the supercooled liquid after optical breakdown and plasma formation. The subsequent collapse and disintegration of the bubble into fragments was observed to be followed by ice crystal nucleation in many, but not all cases. Details of the crystallization events have been investigated by high-speed imaging, and nucleation statistics and crystal growth rates are given. It is argued that homogeneous nucleation in the compressed liquid phase is a plausible explanation of the effect.
A commercial ultrasonic probe was used to study emulsification of an o/w system (5 wt% soybean oil stabilised with 1 wt% Tween 80 in water). Two different sets of experiments were performed. Firstly, we investigated the effect of power, duty cycle and ultrasound time on the production of an oil-in-water emulsion from a coarse pre-emulsion mix. The droplets reached a stable size (0.7 microm) within 5 min independent of the power and duty cycle used. Secondly, the mechanism of emulsification was studied by observing the emulsification process at an oil-water interface (no pre-mix) with a high-speed camera. Transient cavitation is thought to be responsible for acoustic emulsification; however there have been no measurements to relate the transient cavitation zone to the production of an emulsion. It has already been shown that the transient cavitation in probe systems is directly under the probe tip. High-speed observations showed that an emulsion could only be obtained if the interface was within a few millimetres of the probe tip. These results strongly suggest that the transient cavitation zone is responsible for the acoustic emulsification of oil.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.