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Title: Acoustoelectrochemical characterisation of cavitation and its use in the study of surface processes
Author: Offin, Douglas Graham
ISNI:       0000 0001 3455 1722
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 2006
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The environment in the vicinity of an operating ultrasonic horn is characterised through the use of electrochemical, acoustic and luminescent techniques, high-speed video and laser scattering. The sound field produced by the horn is modelled and acoustic pressure measurements are made. The acoustic pressure is greatest at the tip of the horn and decrease as the axial distance is increased. In the presence of cavitation the pressure wave is complex, consisting of a sinusoidal driving wave superimposed with high amplitude pressure shocks every 3-4 cycles of the driving wave. The shocks are attributed to emissions from cavitation activity. The spatial extent of inertial cavitation is investigated using multibubble sonoluminescence (MBSL) imaging and a novel electrochemical erosion technique. The electrochemical technique utilises a novel Pb/Pt dual microelectrode, which has the ability to detect both the mass transfer and erosive effects of sonication and cavitation. Inertial cavitation only exists close to the horn but is found to extend further than expected. This is because the introduction of an electrode can have a significant effect on the sound field, due to scattering of the incident pressure waves. It is found that the degree of scattering depends on the wavenumber, radius of the electrode, position on the electrode surface and the acoustic properties of the electrode and solution. It is shown that under the conditions used here the driving wave is not scattered significantly by the electrode. However, the high frequency shock waves are scattered effectively. The degree of scattering is shown to be greater for a soda glass-bodied electrode when compared to an Epofix epoxy-bodied electrode.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available