Fluid mixing in stirred vessels is widely encountered in a number of industries. In this work, different experimental techniques and the CFD modelling approach are used to measure the mixing of a wide range of fluids in stirred vessels. As the detailed validation is essential for CFD modelling, CFD predictions are compared in detail with different experimental measurements. The capability of CFD modelling of the 3D spatial distribution of velocity and solid concentration within opaque concentrated solid-liquid suspensions with the mean solid concentration up to 40 wt% is assessed by comparing with the experimental data obtained from positron emission particle tracking (PEPT) measurements. Because the impeller configuration is of significant importance to the flow pattern, the performance of different impellers for single-phase mixing of Newtonian and non-Newtonian fluids in stirred vessels is compared. CFD predictions of flow fields generated from different impellers are compared with those measured by the well-established particle image velocimetry (PIV) technique. The capability of CFD modelling of different mixing features of non-Newtonian fluids in stirred vessels are verified by comparing with experimental data obtained from PIV, PEPT, and planar laser induced fluorescence (PLIF) measurements.

Several unscheduled shut downs of the Cruas nuclear power plant in France have been caused by the deposition of corrosion products in flow broaches of the steam generator tube support sheets. The depositions are theorised to be the result of electrokinetically stimulated deposition. In this work, a hot water loop to replicate these depositions in the laboratory was built, along with rigs to characterise supporting phenomena – the corrosion rate of stainless steel and the solubility of the corrosion products. While the data obtained from the hot water loop did not provide conclusive proof of the existence or prevalence of the electrokinetically stimulated deposition mechanism, evidence of deposition caused by cavitation was found. The corrosion rate of stainless steel was measured at high temperatures in solutions of lithium hydroxide at various concentrations. Surface finish was found to have an effect on the corrosion rate, though the difference between mechanically ground surfaces with an order of magnitude difference in roughness was found to be minimal. The solubility of the corrosion products formed was measured and found to be of similar order to that reported in the literature, however the minor alloying elements were found to leach from the surface in substantial quantities.

An experimental study was carried out concerning the optimization of catalyst type, operating conditions, addition of water and hydrogen for use in the THAI-CAPRI process and is reported. Three feeds namely, THAI field oil, Combustion Cell Oil (CCO) and n-decane were used in the presence of catalyst or an inert medium for comparison. Experiments were carried out using micro-reactors containing 5 g catalyst under different temperatures, pressures and gas environments. It was found that there was a trade-off in operation temperature between upgrading performance and catalyst lifetime. At higher temperatures of 500 °C led to an average of 6.1 °API upgrading , however, the catalyst lifetime was limited to 1.5 hours. Operation at 420 °C was found to be a suitable compromise, with upgrading limited up to 3 °API, with catalyst lifetime extended to 77.5 hours. From the results of the current study it can be said that by careful control of the temperature and oil flow rate in the in-situ CAPRI process, additional upgrading compared with the THAI process alone may be effected, resulting in a more valuable produced oil, which is easier to transport and could be further processed into distillates.

This thesis presents an investigation into the morphology of palladium (Pd) size selected clusters and industrial Pd catalysts using high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) technique. The driving force of this work is to establish reliable and efficient methods for the structural characterisation of nanostructures. The characterisation of nanostructures is essential to our fundamental understanding of cluster use within applications, such as catalysis. The complexity of the morphology of industrial catalysts presents a significant challenge to rapid screening techniques. This thesis presents an efficient method which uses size selected clusters as mass standards in STEM based mass spectrometry. Size selected clusters were created using a radio frequency magnetron sputtering cluster beam source in conjunction with a lateral time of ight mass selector, Pd clusters were soft-landed onto amorphous carbon grids between the size range of N = 454 to 10,000 (\(\pm\)4%), with a deposition energy of 500 eV. The quantitative image analysis allows one to gain insight into each catalytic Pd particle and, in combination with two-dimensional diameter measurements, evaluate the three dimensional morphology of the particles. The use of the cluster source has also allowed investigation into the formation mechanisms of nanostructures, finding specific size-dependant morphological features for Pd clusters. Elongation of Pd clusters has been observed for cluster sizes of \(\geq\) 2000 atoms, as well as the onset of voids within the cluster structure for sizes \(\geq\) 2622. HAADF-STEM analysis has proved to be an invaluable tool in the determination of cluster size, independent of morphology, as well as enabling specific structural features within clusters to be revealed. An investigation into the atomic structure of supported Pd\(_{887}\) clusters is also presented. Specific structural motifs are identified using aberration corrected STEM within the sample range via direct comparison with simulated HAADF-STEM images of structures simulated using global minimum techniques.

The research presented in this thesis explores the design and fabrication of microstructured and switchable biological surfaces, which may have potential applications of nanobiotechnology. The thesis focuses on the fabrication of biological surfaces which can be controlled via external stimuli. Chapter 1 - Introduction to Nanobiotechnology - presents an introduction to the background of this research including the role of self-assembled monolayers (SAMs) in nanobiotechnology, microstructure fabrication techniques, stimuli responsive surfaces and cell migration. Chapter 2 - Surface characterization techniques - presents surface characterization techniques employed throughout this research. Chapter 3 - Study of Arp2/3 complex activity in filopodia of spreading cells using patterned biological surfaces - presents the fabrication and characterization of patterned biological (fibronectin) surfaces using patterning technology (microcontact printing) and several surface analytical techniques. This study explores the role of filopodia in the spreading of Mouse Embryonic fibroblast (MEF) cells and the function of Arp2/3 complex in this process. The results demonstrated that filopodia, produced by MEF cells interacted with the patterned fibronectin surface and guided lamellipodia protrusion. Arp2/3 complex, which is absent on the filopodia adhesion site, does not facilitate in the adhesion of filopodia on the fibronectin surface. Chapter 4 - Tuning specific biomolecular interactions using electro-switchable oligopeptide surfaces - presents the fabrication of responsive surfaces that rely on electro-switchable peptides to control biomolecular interactions on gold surfaces. This system is based upon the conformational switching of positively charged oligolysine peptides that are tethered to a gold surface. The bioactive molecular moieties (biotin) terminates on the oligolysines can be reversibly exposed (bio-active state) or concealed (bio-inactive state) on demand, as a function of surface potential. Chapter 5 - Experimental procedures, protocols and synthesis - describes the experimental techniques used during the investigations performed throughout the work described in this thesis. Experimental protocols and data analysis by various equipment are described.

Both the fate and behaviour of the nanomaterials in the environment and their effects on the living organisms need to be better understood in order to maintain environmental health and ensure the sustainability of the important nanotechnology industry. This dissertation focused on the effects of gold nanoparticles on the Pseudomonas fluorescens bacteria, as a model of the planktonic bacterial biomass. Citrate capped and PVP Capped gold NPs were synthesized and characterised by measuring their relevant physicochemical properties such as size, shape, zeta potential, surface charge and stability in environmentally relevant ionic strength and in bacterial growth media. The citrate capped AuNPs of (14 nm core size) had no effect on the bacterial growth as no inhibition was recorded when compared with control samples, while similar concentration and comparable sizes of PVP capped gold NPs have affected the bacterial growth as manifested through the reduction of optical density and demonstrated by the TEM images in the form of membrane damage including blebbing formation, tubular structures on the surface of the membrane of the bacterial cells and, in severe cases, the complete bursting of bacterial cells. It was found out that gold ions inhibit completely the bacterial growth as shown by optical density measurements.

The Gas Diffusion Layer (GDL) has the important role of transporting the reactants into, and products out of the cell. This study aims to provide insights for understanding the relationship between GDL properties and the performance of PEFCs. Ex-situ characterisation techniques were employed to study the mechanical, physical and electrical properties of the GDL. The relationship between the various properties of GDL was investigated and discussed in this work. The study shows that characteristics such as GDL thickness, bulk density, PTFE and MPL content, porosity, hydrophobicity, permeability and electrical conductivity are closely connected. The effect of compression on the cathode GDL performance in PEFC membrane electrode assembly (MEA) is discussed using Polarisation (IV) curve and electrochemical Impedance Spectroscopy (EIS). Compression affects the electrical and mass transport properties of the GDL and therefore needs to be optimised. The results show that there is an optimum compression point, at which; a minimum contact resistance and optimum water transport are achieved. The optimum compression level is dependent on the GDL properties. The optimum compression ratio varies for the different GDLs according to the difference in the material properties. At optimum compression, the performance of the different GDL materials was compared to understand the effect of the GDL properties on the performance. GDL characteristics such as structure, thickness, bulk density, PTFE loading, and MPL presence have a direct effect on the MEA performance and need to be optimized for the different PEFC applications.

This thesis reports numerical analyses of powder flow, mixing and segregation behavior during die filling in a vacuum and in air using an Eulerian-Lagrangian model, which employs a Discrete Element Method (DEM) for the particles and Computational Fluid Dynamics (CFD) for the air with a two-way air-particle interaction coupling term. The effects of air and particle properties (size, density, size distribution, cohesion etc.) on powder flow are explored. The results are in a good agreement with experimental observations. Powder flow is characterized in terms of a dimensionless mass flow rate and a critical filling velocity. When air is present, the powder flow characteristics depend on the particle size and density and can be classified into an air-sensitive regime and an air-inert regime. It is found that the difference in particle size and/or density can cause segregation during die filling. Therefore, parametric studies are undertaken to examine the effects of some factors, such as particle size or density ratio, shoe speed, initial mass fraction of fine particles, initial height of powder bed and cohesion. Suction filling with a movable punch is also simulated. It has been shown that the utilization of suction can significantly improve the powder flow rate and reduce the density-induced segregation.

The thesis starts with characterization of alginate that involved the viscosity, ageing, and degradation of different concentrations of alginate. Live/Dead, MTT, and Hoechst 33258 assays were used to investigate cell viability and proliferation in alginate discs. Pulsed-low intensity ultrasound (PLIUS) treatment was applied to cells encapsulated in alginate to see if it has an effect on viability/proliferation of encapsulated cells (Hoechst 33258 assay), extracellular matrix (ECM) deposition (Alcian blue staining, hydroxyproline and glycosaminoglycan (GaG) assay) and cell morphology (scanning electron microscopy (SEM)). Study of cell behaviour in alginate discs showed that by altering both alginate concentration and cell seeding density, cell proliferation in alginate can be controlled. PLIUS in conjunction with growth factors (ascorbic acid and TGF-β1) leads to a higher amount of collagen production for 3T3 cells when compared to PLIUS alone. However, PLIUS exposure alone leads to a greater increase in HDF cell proliferation and collagen production than when supplemented with growth factors. No effect was seen on chondrocytes when PLIUS was applied. SEM images showed no damage to cells as a result of PLIUS exposure. These results indicate that PLIUS treatment of cells encapsulated in alginate showed a potential effect for enhancing ECM production by cells in culture.

Highly ordered, stable and reproducible TIO\(_2\) NMs were synthesized using different precursors and alcohol mixtures. Various shapes of TIO\(_2\) including spherical NPs with shape factor of 0.9 or more, nanocubes, nanorods and ellipsoids were successfully fabricated. Spherical round anatase and rutile ellipsoids were selected and stabilized with different surfactants including PEG, PVP, sodium citrate and SRFA. Sodium citrate and SRFA proved to be the best stabilizing agents as compared to other surfactants used. The stabilized NMs were tested for their aggression kinetics in the presence of mono and divalent electrolytes (NaNO\(_3\), NaCl, CaN\(_2\)O\(_6\), CaCl\(_2\)). The aggregation kinetic studies showed that rutile ellipsoids behaved well against different mono and divalent cations. The CCC's observed for sodium citrate stabilized NMs were significantly higher than SRFA stabilized NMs, showing that sodium citrate is a better stabilizing agent than SRFA. The SRFA and sodium citrate stabilized NMs were studied for porous media column transport. The mobility of the rutile ellipsoids was greater than spherical anatase. Bare anatase NPs gave no breakthrough and the NPs clogged both the sandstone and glass bead columns; while bare rutile ellipsoids gave nearly 100% breakthrough curves. Only 40% or less NPs were released from sandstone columns. More release of NPs with SRFA flush is also important as it reflects the ultimate fate and behaviour of TiO\(_2\) NPs in natural environment which is rich in humic substances.