Ti has been widely used in biomedical fields since the 1950s because of biocompatibility, corrosion resistance and suitable mechanical properties. However, corrosion-related failures of Ti implants are observed. Ti corrosion products are reported to induce unfavourable biological responses, which may lead to failures of Ti implants. Corrosion of three grades of Ti (CP-Ti Grade2, CP-Ti Grade4 and Ti6Al4V) in simulated peri-implant environments was investigated by solution analysis, surface analysis and electrochemical tests. Lipopolysaccharide, a component of bacterial cell walls and a mediator of peri-implant inflammation, was observed to enhance Ti corrosion in slightly acidic and neutral conditions (pH 4-7) whilst it inhibited Ti dissolution in highly acidic environments (pH 2). Both albumin, an abundant protein, and H₂O₂, an important inflammation product, influenced corrosion of Ti6Al4V and the co-existence of both species considerably enhanced Ti release than either species in isolation. The β phase of Ti6Al4V was preferentially attacked in H₂O₂. The presence of an early coloniser of dental implants Streptococcus sanguinis and human neutrophils, abundant immune cells, promoted Ti release. Mechanically-assisted crevice corrosion simulation was demonstrated with development of aggressive crevice chemistry. Albumin decreased the abrasion charge of Ti6Al4V while LPS and H2O2 did not show a measurable change.

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.

Self-healing composites are composite materials capable of automatic recovery when damaged. They are inspired by biological systems such as the human skin which are naturally able to heal themselves. Over the past two decades, two major self-healing concepts – based respectively on the use of capsules and vascular networks containing healing agents - have been proposed and material property recovery has been enhanced from 60% to nearly 100%. However, this improvement is still not sufficient to allow self-healing composites to be applied in practice because the healing capability varies with many external factors such as ambient temperatures and damage conditions. The key to the practical application of self-healing composites is to promote the sustainability of healing capacity to make the recovery robust. The thesis presents various techniques to enhance the healing capacity of fibre-reinforced composites to realise strong recovery regardless of ambient temperatures or material types. It presents the effects of various popular configurations of vascular networks on the flexural properties and healing performances of fibre-reinforced composites. The thesis demonstrates a design enabling recovery at ultra-low temperatures by using hollow vascular networks and porous heating elements. It also presents a new healing mechanism to repair the broken structural carbon fibres by incorporating conventional healing agents with short carbon fibres which could be aligned in an in situ electric field. The mechanism was also adopted to enable the restoration of the conductivity of a fibre-reinforced composite incorporating a porous conductive element, a carbon nanotube sheet, which could be used as a heating actuator or a sensing component. Thus, the development reported in this thesis have contributed to promoting the sustainability of the recovery of self-healing composites.

Atmospheric corrosion of aluminium alloy AA2024 was investigated using in situ synchrotron micro-tomography, which allows visualisation in a non-destructive manner in real time. The effect of atmospheric variables such as salt type, humidity, exposure time and salt deposition density on the corrosion rate was investigated. It was found that corrosion fissures grow along grain boundaries parallel to the rolling direction of the alloy, reaching a limiting depth, and then spread laterally. The volume of corrosion increases with salt density and relative humidity. Salt type has a limited effect on the volume of corrosion in microtomography measurements where the droplet is constrained at the top of a pin, but in parallel lab-based experiments on plate surfaces, it was found that NaCl and simulated ocean water droplets spread laterally, leading to increased corrosion owing to an increase cathodic area, whereas pure MgCh and CaCh droplets do not spread. Preliminary microtomography work on cycling the relative humidity showed transient increases in localised corrosion during wetting and drying phases, often associated with rapid growth of pmt of a localised cmTosion site, or initiation of new sites.

This document is a compilation of my selected research publications in micro and nano fabrications. The papers are largely arranged in chronological order to show the development of research interests. The research works are grouped into three sections. Section one consists of 34 research papers on micro fabrication in various materials. The research was motivated by the development of a finger nail sized micro engine as explained in Papers 1 and 2. Section two of the document includes some research activities and achievements on nanocomposite materials embedded in metallic and ceramic matrices. Section 3 includes the papers to reflect the research in developing nanostructure fabrication processes. The research contained in this DSc submission shows a continuous exploration and development of novel micro/nano fabrication processes. Although the submission covers research activities spanning 15 years, from 2000 to 2015, many of the research results represent the top technology of the time. They have contributed to the ever progressing manufacturing capability of the world. The research has encompassed both theoretical and experimental studies, contributing to the understanding of the processes and materials involved.

This thesis describes computational studies, syntheses and characterization of Cu-Au, Pd-Au, and Pt-Au bimetallic nanoparticles. The computational methodology is a combination of a genetic algorithm coupled with an empirical potential and density functional theory, which is used to study theoretically the geometrical structure, chemical configuration, and electronic properties of 38 atom Cu-Au and 40-atom Pt-Au nanoparticles. Experimental Cu Au and Pt-Au nanoparticles are synthesized by wet-chemical methods: the two-phase method combined with a galvanic exchange procedure (dodecanethiol-stabilized Cu-Au nanoparticles), the polyol method (Polyvinylpyrrolidone stabilized Pt-Au nanoparticles), and the Turkevich-Frens method combined with a successive reduction procedure (citrate-stabilized Pt-Au nanoparticles). The Pd-Au nanoparticles which are characterized in our work were synthesized by a microbial method. The nanoparticles are characterized using transmission electron microscopy (TEM) and scanning TEM (STEM) combined with high angle annular dark field (HAADF) imaging, energy dispersive X-ray elemental mapping using a silicon drift detector (SDD), tomography, and electron energy loss spectroscopy (EELS). Sizes and shapes of the Cu-Au, Pd-Au, and Pt-Au nanoparticles are studied by TEM. Morphological evolution and aggregation of the Cu-Au nanoparticles are also observed under the TEM electron beam. SDD-EDX elemental mapping combined with HAADF contrast is used to study the chemical configuration of all the three systems. HAADF-STEM tomography is performed for the Pd-Au nanoparticles. Surface plasmon resonances of the Cu-Au and Pd-Au nanoparticles are studied using EELS. The structures and configurations of the theoretical bimetallic clusters and the experimental bimetallic nanoparticles are found to be composition-dependent.

The development of the alternating current field measurement (ACFM) technique for high-speed inspection of railway wheels/track is important to ensure the integrity of railway assets. The stress and conditions at the wheel/rail contact patch, severity of rolling contact fatigue (RCF) damage and changes in microstructure and hardness with tread depth for railway wheels are investigated. This study employs experimental measurement of RCF defects in railway wheels to understand ACFM sensor signal - RCF defect relationships. The influence of sensor frequency and speed, sensor angle relative to crack angle, lift-off distance, crack propagation angle and inter-crack spacing distance are investigated. Low rather than high frequency sensors are better suited at sizing cracks in railway wheels and track. The optimum signal is obtained when the sensor is oriented parallel to the crack angle. The signal is reduced at higher speeds. The maximum change in the normalised Bx signal component of the sensor’s magnetic field is greater for closely spaced cracks (< 5 mm) and thus overestimates the defect. Inter-crack spacing distances of 15-20 mm yield estimates for crack pocket depths that are oversized by 20-36%. The inner cracks in a cluster with four defects yields higher Bₓ values than expected and thus significantly over sizes the defects at 15-20 mm inter-crack spacing distances, whereas, the sensor provides reasonable depth estimates for the outer cracks. Crack propagation angle affects the signal. Scans conducted with the probe oriented at 90° to the cluster of cracks consisting of a deep central crack surrounded by shallow cracks results in a distinct central sensor Bₓ signal that consists of a peak due to a flux leakage effect, thus, identifying the critical defect.

Microporous materials (with pores of less than 2 nm in diameter) have attracted considerable attention due to the variety of applications such as gas storage. Physisorption of molecular hydrogen offers several advantages over chemical absorption, namely, fast kinetics and complete reversibility. The overall aim of this work was to investigate the potential of microporous materials for hydrogen storage, with particular attention given to a relatively new class of material: Polymers of Intrinsic Microporosity (PIMs). Generally the PIMs were seen to adhere to Chahine’s rule, which predicts a linear correlation of hydrogen adsorption capacity, at 77 K, with surface area (1 wt.% per 500 m\(^2\) g\(^{-1}\)). IRMOF 1 and Cu-BTC exhibited the largest gravimetric storage capacities of 4.86 and 4.50 wt.% at 77 K and 15 bar, respectively. The largest for a microporous polymer was 3.26 wt.% at 77 K and 15 bar, for the methyl triptycene-based PIM. Two empirical equations, Sips and Tóth, were used in addition to a multi-parameter Virial type thermal equation to fit hydrogen adsorption curves over a range of temperatures (77 to 137 K), in order to calculate the enthalpy of adsorption for all materials as a function of hydrogen adsorption. The findings in this investigation suggest that there is a trade-off between gas sorption capacity and enthalpy of adsorption where dispersive van der Waals interactions dominate adsorption. It is unlikely that the optimal enthalpy of adsorption (of ca. 20 kJ mol\(^{-1}\)) will be achieved by simply reducing the pore size of the material.

Implanted titanium (Ti) devices such as dental implants have been shown to produce metallic species within adjacent tissues. The effect of the presence of these species within oral epithelial tissues is currently not well characterised or known. This thesis investigates the effects of TiO\(_2\) nanoparticles (TiO\(_2\) NPs) at a range of concentrations on oral epithelial cells in the context of cell viability, cellular functions and interactions via a variety of methods. A co-culture model was established, and the difficulties of using a nano-scale insoluble stimulus were explored, and high content screening techniques were shown to be potentially more appropriate methods than conventional assays in this context. Interactions between TiO2 NPs and oral epithelial cells were imaged and investigated using a variety of imaging techniques. Oral epithelial cells were shown to take up TiO\(_2\) NPs within vacuole type structures. Cell viability appeared to not be affected at lower concentrations. Gene expression changes of oral epithelial cells in response to TiO\(_2\) NPs in the presence and absence of pathogenic bacteria were investigated. Cytokines important in cell-cell signalling were shown to bind TiO\(_2\) NPs, therefore creating potential for TiO\(_2\) NPs within tissues to modify immune responses within tissues adjacent to implanted Ti devices.