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An investigation of electrochemical single bubble sonoluminescence

An investigation of electrochemical single bubble sonoluminescence
An investigation of electrochemical single bubble sonoluminescence
A technique for stable and reproducible electrochemically generated SBSL events (eSBSL) is presented. This approach is shown to have some advantages over conventional seeding methods. These include control of the initial gas flux and control of the initial SBSL bubble composition within the same media (e.g. the ability to seed with H2 and O2 for example). Comparison of different cell types shows that a cell setup based on conventional round bottomed flasks is the most appropriate for eSBSL generation. Typically a critical current (-0.11 mA) is required to generate a hydrogen seeded eSBSL event from a 50 ?m diameter Pt electrode while oxygen seeding requires +0.15 mA under the same conditions.

Two types of bubble dynamics are observed when high-speed imaging is employed to study the eSBSL event behaviour. Most of the bubbles oscillate repetitively in a non-linear fashion as expected. However, some bubbles fragmented into clusters of smaller bubbles before coalescing in a repetitive fashion. The eSBSL event is shown to be extremely sensitive to experimental parameters such as the acoustic pressure amplitude, solution temperature, solution composition, applied frequency and local environment. In particular trace noble gase (Ar) is shown to affect the eSBSL event characteristics. At Ar concentrations below 0.3 ?mol dm-3 (determined by a residual gas analyser) short-lived (10-40 s) and fading eSBSL events are observed. The emission spectra showed a red centred ‘black body like’ character in disagreement with the available literature. In addition some evidence for OH* emission is presented for these short lived events. It is proposed that these eSBSL events contain primarily gas they were seeded with. At higher Ar concentrations (0.3-1.5 ?mol dm-3), long-lived SBSL events are observed. These tend to produce two kinds of emission spectra. One is a blue centred spectrum and second is a double-peaked red-blue spectrum. It is postulated that these eSBSL bubbles initially contain the gas they were seeded with but are gradually converted to an Ar rich noble gas SBSL event from the solution. At higher solution gas concentrations no stable SBSL could be observed. Emission lifetime is measured using time correlated single photon counting (TCSPC). The FWHM values for hydrogen/oxygen seeded eSBSL events are in the range of 290-315 ps under the conditions employed.
Shulyak, Raissa
b663dc95-7df5-4fd8-bce2-aace5a4691a6
Shulyak, Raissa
b663dc95-7df5-4fd8-bce2-aace5a4691a6
Birkin, Peter
ba466560-f27c-418d-89fc-67ea4f81d0a7

Shulyak, Raissa (2014) An investigation of electrochemical single bubble sonoluminescence. University of Southampton, Chemistry, Doctoral Thesis, 214pp.

Record type: Thesis (Doctoral)

Abstract

A technique for stable and reproducible electrochemically generated SBSL events (eSBSL) is presented. This approach is shown to have some advantages over conventional seeding methods. These include control of the initial gas flux and control of the initial SBSL bubble composition within the same media (e.g. the ability to seed with H2 and O2 for example). Comparison of different cell types shows that a cell setup based on conventional round bottomed flasks is the most appropriate for eSBSL generation. Typically a critical current (-0.11 mA) is required to generate a hydrogen seeded eSBSL event from a 50 ?m diameter Pt electrode while oxygen seeding requires +0.15 mA under the same conditions.

Two types of bubble dynamics are observed when high-speed imaging is employed to study the eSBSL event behaviour. Most of the bubbles oscillate repetitively in a non-linear fashion as expected. However, some bubbles fragmented into clusters of smaller bubbles before coalescing in a repetitive fashion. The eSBSL event is shown to be extremely sensitive to experimental parameters such as the acoustic pressure amplitude, solution temperature, solution composition, applied frequency and local environment. In particular trace noble gase (Ar) is shown to affect the eSBSL event characteristics. At Ar concentrations below 0.3 ?mol dm-3 (determined by a residual gas analyser) short-lived (10-40 s) and fading eSBSL events are observed. The emission spectra showed a red centred ‘black body like’ character in disagreement with the available literature. In addition some evidence for OH* emission is presented for these short lived events. It is proposed that these eSBSL events contain primarily gas they were seeded with. At higher Ar concentrations (0.3-1.5 ?mol dm-3), long-lived SBSL events are observed. These tend to produce two kinds of emission spectra. One is a blue centred spectrum and second is a double-peaked red-blue spectrum. It is postulated that these eSBSL bubbles initially contain the gas they were seeded with but are gradually converted to an Ar rich noble gas SBSL event from the solution. At higher solution gas concentrations no stable SBSL could be observed. Emission lifetime is measured using time correlated single photon counting (TCSPC). The FWHM values for hydrogen/oxygen seeded eSBSL events are in the range of 290-315 ps under the conditions employed.

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Published date: 1 September 2014
Organisations: University of Southampton, Chemistry

Identifiers

Local EPrints ID: 369353
URI: http://eprints.soton.ac.uk/id/eprint/369353
PURE UUID: 4aede798-6bff-4efd-bc14-5e78a927a2ab
ORCID for Peter Birkin: ORCID iD orcid.org/0000-0002-6656-4074

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Date deposited: 27 Oct 2014 12:09
Last modified: 05 Oct 2019 00:39

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Contributors

Author: Raissa Shulyak
Thesis advisor: Peter Birkin ORCID iD

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