In the light of the recent research interest in emulsion formation, this PhD thesis seeks to expand the current body of knowledge regarding the role of various emulsifiers on emulsion formation mechanisms. This study is particularly relevant to the food industries, where formulated emulsions often result in complex microstructures. Therefore, controlling the production processes requires knowledge regarding the effect of individual constituents on the final product. The experimental investigation presented here examines emulsion behaviour during processing. Attempts have been initially focused on the development of a technique (reflectance technique), and subsequently a methodology, to investigate droplet size evolution during processing. This technique is based on the relationship between reflected light from the emulsion and the droplet size, at any given dispersed phase volume fraction, and emulsifier type. Consequently, measurements of the ‘light reflectance’ during the process can be used to determine the droplet size evolution in real-time. This technique was applied to the study of emulsification in batch mixing systems. The developed methodology was used to investigate the effect of various operating parameters and formulations on the droplet size evolution during processing. These parameters include: the emulsifier type (surfactants, proteins, solid particles and mixed emulsifier systems) and concentration; hydrodynamic condition of the process; and the dispersed phase volume fraction. It was shown that using emulsifiers results in a higher droplet break-up frequency at the early stages of the process. The break-up frequencies remained the same in the presence of a range of emulsifier concentrations. Out of all the emulsifiers used, silica particles showed II the lowest droplet break-up frequency. This is because the interfacial tension is not affected when silica particles are adsorbed on the interface of droplets. It was further shown that the final droplet size is mostly affected by the extent of droplet break-up, whilst droplet coalescence has minimal influence. Therefore, using a higher concentration of emulsifier results in a lower final droplet size, as a consequence of higher adsorption rate of remaining emulsifiers in the aqueous phase, which in turn increases the droplet break-up frequency through decreasing the interfacial tension. This hypothesis was demonstrated by using solid particles in emulsification which showed similar final droplet size to the experiment in the absence of added emulsifier, since interfacial tension is not affected by their adsorption. It is demonstrated that the droplet coalescence cannot be completely suppressed by the presence of surfactants (Tween 20) or proteins (sodium caseinate or WPI), due to the desorption of these emulsifiers from the interface. On the other hand, droplet coalescence was arrested in the presence of solid particles, since their adsorption can be considered an irreversible phenomenon. When the dispersed phase volume fraction was increased up to 50 %, a minimum was observed in the droplet break-up frequency at the dispersed phase volume fraction of 20 %. This was caused by the influence of two opposing factors; the increase in the dispersed phase volume fraction dampens the energy dissipation in the system, which tends to decrease the droplet break-up. In contrast, larger droplets are involved in break-up phenomena at higher dispersed phase volume fractions, which promote the droplet breakup. Increasing the dispersed phase volume fraction, on the other hand, resulted in a decrease in droplet coalescence, caused by an increase in the dampening effect of the dispersed phase, which decreases the energy dissipation in the system.

Manufacturers are under pressure to reformulate products to make healthier foods, without changing desirability or flavour. A better understanding of product breakdown under oral conditions is essential to structure novel products which are healthier without consumers noticing. In-vitro methods were developed to explore product behaviour when subject to a range of phenomena relevant to those in the mouth, with particular emphasis on lubrication behaviour. Polysaccharides common in food products were mainly used as model systems and salt release was studied in some systems. Three in-vitro systems were developed and used in this study. Firstly, a stirred vessel was developed to gather data of salt release from gelatin, gellan and alginate systems, under quiescent conditions. This was a reliable method of tracking diffusion of sodium ions through the gel structures into a surrounding liquid, showing that diffusion was unaffected by the differing structure of the gels. The second system introduced the effect of compression. Only when pressures are sufficient to rupture the gel samples did compressions affect salt release over that observed in the stirred vessel study. Samples released the majority of their contained salt up to nine times faster, as a result of greater surface areas being exposed. Finally, tribology equipment was developed, which explores the thin film, high shear behaviour of materials. An exploration of available equipment, processing parameters and configurations was carried out to determine optimum surfaces, normal forces and speed ranges which could be related to phenomena occurring in the mouth. The lubricating properties of inhomogeneous polysaccharides with different physical properties were studied. The mixing behaviour of the polysaccharide greatly affected the lubrication response; some mixed quickly so lubricated more efficiently and vice versa. Finally, the developed tribology equipment was used to study the ordering process of a series of fluid gel samples, indicating that lubrication tracks the ordering process, with a decrease in lubrication when structure forms. The pattern of this response is a result of polysaccharide and salt content of the materials, with increasing content enhancing the change in lubrication experienced as more rigid gel particles are produced. The work presented in this thesis shows that the use of in-vitro methods can provide repeatable information on structure behaviour under conditions relevant to the mouth. This information could then be used to develop and assess future food products for their expected performance when consumed.

Total disc arthroplasty (TDA) can be used to replace a degenerated intervertebral disc in the spine. There are different designs of TDAs, but one of the most common is a ball-and-socket combination. Contact between the bearing surfaces of such designs can result in high frictional torque, which can then result in wear and implant loosening. This study was designed to determine the effects of change in design factors, such as dimensions and material combinations, on friction and wear of ball-and-socket TDAs. Friction tests were carried out on generic models with ball radii 10, 12, 14 and 16 mm. Three material combinations were investigated; metal-on-metal, metal-on-polymer and for the first time polymer-on-metal. Wear tests were performed on metal-on-polymer Charité® TDAs and generic metal-on-metal models to compare the wear rate under the same conditions. Friction test results showed that polymer-on-metal TDAs create less friction than metal-on-polymer and metal-on-metal TDAs. Wear test results showed that under the same conditions, metal-on-metal TDAs create 23 times less wear debris than metal-on-polymer. The results were in agreement with studies on total hip arthroplasty (THA). The results of this work suggest possible alternatives for future TDA designs.

Pit propagation in stainless steels under electrochemical control was investigated using in situ synchrotron X-ray microtomography, which was used to confirm that the lacy covers commonly found for pits in stainless steels grow through perforation of the metal surface by upward growth of rapidly dissolving lobes from the main pit. In situ synchrotron X-ray radiography has been used to observe the evolution of 2D pits growing at the edge of stainless steel foils under electrochemical control in chloride solutions. Pit growth shape, kinetics and stability under current and potential control at various bulk chloride concentrations have been studied. It was found that the pit depth tends to grow under diffusion control, whereas lateral development is influenced by solution conductivity. The impact of the perforated cover on the pit growth and stability was examined and its formation was found to be similar to the observations from 3D by X-ray microtomography. A method for extracting the key dissolution kinetic parameters from radiographs has been developed. The local anodic current density along the boundary of a pit was directly measured from the rate of advance of the pit into the metal. Then the local metal ion concentration and potential drop inside the pit cavity was back-calculated using transport equations and the requirement to maintain charge neutrality, establishing the relationship between local current density, interfacial potential and metal ion concentration in the solution. The predictive model for pit propagation in stainless steel developed by Laycock and co-workers was examined, its sensitivity to key growth parameters was evaluated, and a modified version of the model was developed based on the kinetic parameters extracted from the radiographic measurements.

Due to some environmental problems for using the common cooling system which works based on the compressor air and cooling gas (Freon), researchers have focused on another type of it. One of the newest methods is using electrocaloric materials to make a cooling system. Electrocaloric effect (ECE) is the reverse of the pyroelectricity which means that the ability of the dielectric materials to change their temperature under electric field. Two ferroelectric materials were selected for this project: BCZT (Ba0.85Ca0.15Ti0.9Zr0.1O3) as a normal ferroelectric and BNT – BT (94 mol% Bi0.5Na0.5TiO3 – 6 mol% BaTiO3) as a relaxor ferroelectric. The results for BCZT shows the best properties with a relative density of 96.1%, the grain size of 32μm, d33 of 410 pC/N and kp of 46% for sintered sample at 1450°C. The highest ECE (∆T= 0.97) was achieved for BCZT sintered at 1450°C (∆T= 0.97). The best properties were founded at BNT-BT sintered at 1125°C with a relative density of 97%, the grain size of 3.2μm, d33 of 165 pC/N and kp of 47%. BNT-BT shows high ECE ∆T= -2.91 and -2.1°C for sintered sample at 1125 and 1150°C respectively under 50 kV/cm which due to two step calcination process is higher than previous researchers.

Themosetting resins are being used increasingly as matrix materials in advanced fibre-reinforced composites. It is well known that the processing conditions used to manufacture the composite can have a major influence on its mechanical integrity in service. In addition, the processing parameters can also affect the ingress of moisture in thermosetting resin and composites. The feasibility of using optical fibre-based sensor systems for monitoring cross-linking reaction has been demonstrated previously. However, little work has been reported on the deployment of a single sensor to study the cross-linking kinetics and the diffusion of moisture. In the current work, four low-cost sensor designs were evaluated for in situ monitoring of the cross-linking reactions of an epoxy/amine resin system. One of these sensor designs was selected and used to investigate in detail the cross-linking kinetics. Excellent correlation was observed between the cross-linking data obtained form the sensors and conventional transmission spectroscopy. Semi-empirical models were used successfully to describe the cross-linking behaviour of the epoxy/amine resin system that was used in this study. Subsequent to monitoring the cross-linking reactions, the fibre-optic sensors were used to study the diffusion of moisture in the cross-linked resin system. Conventional gravimetric measurements were also carried out to enable the correlation with the data obtained from the fibre optic sensors. It was demonstrated that the fibre-optic sensors were capable of giving information on the “localised” diffusion of moisture in the neat-resin plaques. Three previously published models were investigated and localised diffusion of moisture in the neat-resin showed non-Fickian behaviour.

Germanium and silicon-germanium have become crucial materials in the silicon photonics field, enabling devices such as high speed photodetectors and high speed modulators to be realised. In order to fabricate efficient and cost effective silicon photonic devices, high quality epitaxial germanium and silicon-germanium growth on silicon, or silicon-on-insulator, is of the utmost importance. In this project, localised single crystal, defect free silicon-germanium on insulator islands have been grown using a rapid melt growth technique. Tailored tree-like structures have been used to modify the cooling rate of the structures during re-growth from the liquid phase. The resulting silicon-germanium composition profiles have been characterised using Raman spectroscopy. Using these tailored tree-like structures, uniform composition silicon- germanium strips have been grown, which is the first time this has been demonstrated using a rapid melt growth technique. Additionally, the ability to locally tune the composition of adjacent silicon-germanium strips has been shown. This enables the possibility of growing a whole range of uniform composition strips, using only a single growth step and a single anneal step, for, amongst others, wavelength division multiplexing applications. Epitaxial growth of germanium on silicon by plasma enhanced chemical vapour deposition has also been studied. Single crystal layers with a defect density of approximately 3.3x108 cm-2 and root mean square surface roughness of 3.5 nm have been demonstrated. It has also been shown that the defect density, surface roughness and crystallinity are all improved with a two minutes, 600 °C anneal. This material has been used to fabricate 12.5 Gbit/s, 0.1 A/W waveguide integrated, zero bias photodetectors for 1550 nm silicon photonics applications, and also, germanium-on-silicon waveguides for mid-infrared silicon photonics applications.

In recent years, it has been recognised that a better understanding of processes involving particulate material is necessary to improve manufacturing capabilities and product quality. The use of Discrete Element Modeling (DEM) for more complicated particulate systems has increased concordantly with hardware and code developments, making this tool more accessible to industry. The principal aim of this project was to study DEM capabilities and limitations with the final goal of applying the technique to relevant Johnson Matthey operations. This work challenged the DEM numerical technique by modelling a mixer with a complex motion, the Turbula mixer. The simulations revealed an unexpected trend for rate of mixing with speed, initially decreasing between 23 rpm and 46 rpm, then increasing between 46 rpm and 69 rpm. The DEM results were qualitatively validated with measurements from Positron Emission Particle Tracking (PEPT), which revealed a similar pattern regarding the mixing behaviour for a similar system. The effect of particle size and speed on segregation were also shown, confirming comparable results observed in the literature. Overall, the findings illustrated that DEM could be an effective tool for modelling and improving processes related to particulate material.

Anaerobic digestion technology has not gained widespread acceptance on UK farms due mainly to the long return on investment periods involved. It has been suggested that co-digestion of agricultural and industrial wastes may enhance the economic viability of such installations. Batch and continuous digestion of cattle slurry and organic industrial wastes was carried out in specially constructed pilot plant digesters, to determine optimum mixtures of waste and digester loading rates. A total of 10 different wastes were tested, on a batch digestion basis, for their potential to co-digest with cattle slurry. Of these, 3 were chosen for continuous pilot plant trials, due to either a need to provide a disposal route for the waste, or positive effects of the waste on methane productivity. Chicken manure was found to slightly enhance methane productivity, but ammonia inhibition of methanogenic bacteria was noted over time. The organic fraction of municipal household waste (OFMSW) significantly enhanced digester methane productivity, while fish offal (FO) slightly enhanced methane productivity when added to the digester in small quantities, but quickly caused digester failure when added in larger amounts. An economic model of a digestion facility was developed and used to show the financial benefits of co-digestion.