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Modelling the effect of acoustic waves on the thermodynamics and kinetics of crystal nucleation from a solution

Haqshenas, SR; (2017) Modelling the effect of acoustic waves on the thermodynamics and kinetics of crystal nucleation from a solution. Doctoral thesis , UCL (University College London). Green open access

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Abstract

A phase transformation in a metastable solution can be affected when it is subjected to high-intensity acoustic waves. Despite the extensive experimental evidence, the nature of this phenomenon has been little studied theoretically. This work aims to tackle this issue and develop the theoretical basis for investigating the thermodynamics and kinetics of crystallisation induced by an acoustic field. In the first part of thesis, we investigated the effect of acoustic waves on the thermodynamics of crystallisation by the aid of the Gibbs droplet model in a generic format. We have developed a new model based on non-equimolecular clusters which can overcome some of the shortcomings of the conventional form of the classical nucleation theory (CNT) in describing the thermodynamics of small clusters. The model is validated by comparing the predicted kinetics of water droplet formation from the gas phase against experimental data. Our results demonstrate a close agreement with experimental data, better than predictions by CNT. In the second part, we studied the kinetics of phase transformation in an acoustic field. We developed a master equation based on a hybrid Szilard-Fokker Planck model, which accounts for mass transportation due to acoustic waves. This model is employed to determine the kinetics of nucleation and the early stage of growth of clusters including the Ostwald ripening phenomenon in an isothermal sonocrystallisation process and is solved numerically for different scenarios in a system with and without mass transportation. Our results show that the effect of pressure on the kinetics of nucleation is cluster size-dependent in contrast to CNT. Furthermore, we calculated mass transportation for different excitations modelled as plane waves propagating in a semi-infinite medium which tends to be rather noticeable only in the case of shock waves. The derivations are generic and can be used with any acoustic source and waveform.

Type: Thesis (Doctoral)
Title: Modelling the effect of acoustic waves on the thermodynamics and kinetics of crystal nucleation from a solution
Event: UCL (University College London)
Open access status: An open access version is available from UCL Discovery
Language: English
Keywords: Phase transformation, Nucleation theory, Gibbs droplet model, Sonocrystallisation, Kinetics of nucleation, Fokker-Planck Equation, Phase transition in acoustic field, Modelling sonocrystallisation, Mass transportation
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Mechanical Engineering
URI: https://discovery.ucl.ac.uk/id/eprint/1553349
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