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Title: Characterisation of emulsion systems using NMR methods
Author: Hollingsworth, K. G.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2004
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Several aspects of emulsion characterisation via NMR are explored. This thesis begins by considering previous experimental work in determining the droplet-size distributions of emulsion systems by magnetic resonance restricted self-diffusion measurements. This is developed by applying regularisation techniques to analyse restricted diffusion measurements and avoid the limitation of fitting a particular functional form for the droplet-size distribution. Droplet-sizing is then extended to flowing emulsions by means of flow-compensated diffusion measurement. The success of this strategy is evaluated for several different model oil-in-water emulsions. An inverse Abel transform technique is applied to produce spatially-resolved droplet-size distributions for both stationary and flowing emulsion systems flowing within a pipe: a significant time saving is achieved by exploiting the symmetry of the system. The flow patterns of emulsions through an orifice plate, an elementary type of static mixer, are then considered. The ability of magnetic resonance to produce spatially-resolved velocity maps is exploited to make rheological measurement of emulsion systems. For the first time, the effect of altering the droplet-phase volume concentration on rheology is considered using magnetic resonance methods and the analysis is extended to emulsions having an apparent yield stress. The phenomenon of shear-induced migration of emulsions, unlike that of solid suspensions, has not previously been well studied: this work presents the first study of this effect by magnetic resonance methods. The effect of changing the volume concentration of droplets, the surfactant and the rotation speed of a Couette geometry are elucidated. One of the principal drawbacks of determining emulsion droplet-size distributions by magnetic resonance diffusion measurements is the time-consuming nature of the measurements: this work thus presents a fast method of making these measurements. This method is exploited to study both emulsion droplet coalescence and emulsion droplet breakup in a simple stirred vessel.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available