The main purpose of this work was to produce nanoparticles with a pure iron core, a narrow size distribution and a high saturation magnetisation in order to improve their effectiveness in the hyperthermia treatment of tumours and in Magnetic Resonance Imaging (MRI) diagnosis. Gas phase Fe nanoparticles in a liquid suspension have been produced by co-deposition with water vapour in ultra-high vacuum (UHV) conditions. The water was injected from outside the vacuum as a molecular beam onto a substrate maintained at 77 K and formed an ice layer with a UHV compatible vapour pressure. Various coating ligands were added to the injected water in an attempt to stabilise the nanoparticle hydrosols. Transmission Electron Microscopy (TEM) images confirmed that the nanoparticles had a pure iron core with a thin oxide shell and a narrow size distribution with the most probable diameter of either 8.55 or 16 nm depending on the source conditions. It was found that short chain molecules are more effective in stabilising the gas phase nanoparticles. The size distribution of the nanoparticles in liquid suspensions analysed by a Nanosight LM10 particle sizer showed that, of the ligands tested, sorbitol and DMSA are the most suitable to prevent the agglomeration of the gas phase produced hydrophobic nanoparticles. UV-visible spectral measurements showed that DMSA coated nanoparticles transform into an oxide in a short time. In addition, a magnetometry study of sorbitol-coated iron nanoparticles showed that oxidation of the nanoparticles erodes the pure iron core to about 5 nm diameter in two months. MRI measurements of the sorbitol-coated iron nanoparticles show that their relaxivity is five times higher than commercial iron oxide nanoparticle suspensions (Resovist®). On the other hand, specific absorption rate (SAR) measurements of the nanoparticles by two different designs of heating coils were not accurate due to the low concentration of nanoparticle in solution. Hence, the heating performance of the nanoparticles was determined theoretically using a new model published by Vallejo-Fernandez [Vallejo-Fernandez 2013], which includes the heating mechanisms active over the whole size range of particles. The results show that the SAR of the pure iron core nanoparticles is significantly higher than iron oxide nanoparticles. Core-shell nanoparticle can also be produced in the gas phase by passing the core nanoparticles through hot crucible loaded with the shell material under UHV conditions. Composite Fe@FeO-Ag nanoparticles which can be used for multifunctional medical applications have been produced. It was also found that heating the nanoparticles in the gas phase using the empty crucible enabled the control of the nanoparticles’ shapes, which was found to change their MRI relaxivity.

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This thesis presents a new methodology for high precision nanoscale machining using Focused Ion Beam (FIB) processes. The methodology is supported by several novel models and methods developed during the PhD project. Gallium focused ion beam instruments are capable of processing virtually any material with a nanometre resolution. This has established FIB based instruments as invaluable specimen preparation tools in material science and circuit editing and failure analysis tools in the semiconductor industry. So far, the technique has had limited application in nano and micro- manufacturing, due to the high cost of the equipment and the long process cycle times required . Nonetheless in recent years it has been demonstrated that FIB can be a viable manufacturing technology if employed in the fabrication of high precision replication tools and it has the potential to replace existing electron and photon lithography techniques. One of the current problems is that the existing FIB procedures developed for material science are often not optimised for quality and efficiency or not applicable in manufacturing. A new machining methodology has been proposed that can be used as a guide to optimise FIB processes for improved efficiency and production quality. The methodology systematically looks into the material selection, the choice of gas precursor and the optimisation of the scanning parameters. To accomplish this several new models and methods are developed. A raster scanning model is proposed that links the probe current, the dwell time, the number of loops and the step with the key process parameters of refresh time, exposure time, dose, and dose distribution. Furthermore, a new term apparent beam size and a method for its measurement are suggested as an alternative to the commonly used "knife edge diameter". The apparent beam size is found to be material and precursor dependent and together with the overlap is accounted for as a key factor in the dose uniformity criterion formulated in the project.

Elastomeric diaphragms are used in the Smart Stabilizer/Weatherford rotary steerable systems (RSS) used in directional drilling down hole. The diaphragms need to operate correctly for the RSS to function effectively. The diaphragm separates the mechanical parts of the RSS, operating in hydraulic oil, from the outside environment. Failure of the diaphragm can lead to failure elsewhere in the RSS. Such failure is likely to have catastrophic consequences for the RSS and, associated with these, very high costs. The diaphragms are subjected to hostile conditions including high temperature and high pressure and the presence of chemical agents. Moreover, monitoring of the behaviour of the diaphragm in service is extremely difficult due to the nature of a drilling process. There is, however, a need for understanding the behaviour and failure mechanisms of such diaphragms; especially with plans to extend the depth of the drilling borehole. In this PhD project an outline design guide is developed for failure avoidance of the diaphragm down hole. Besides proposing an outline for such a design guide and identifying hypothetical modes of failure, detailed analyses of the normal behaviour of the diaphragm down hole and the failure due to fracture are also performed. A large part of the project is focused on gaining understanding of the normal behaviour of the diaphragm down hole. This is identified as being of a great importance in failure avoidance. Analytical, numerical and physical methods are employed here to allow for prediction of such behaviour. Those are supported by forensic examination of used diaphragms. Mechanisms of failure leading to fracture are proposed. Crack growth is investigated via the strain energy release rate approach. Three “ingredients” for failure are examined in the context of the conditions down hole: stress/strain characteristics, crack growth rate as a function of the strain energy release rate (including catastrophic tearing) and intrinsic flaw size or cut. The outcome is then verified in service-related tests on the actual diaphragms.

This thesis describes the investigation and development of a novel CAD-based aerodynamic optimisation system, with the aim of allowing gradient-based optimisation of feature-based, parametric models within commercial CAD packages in timescales acceptable for industrial design processes. The process developed is based on linking parametric design velocities (geometric sensitivities computed from the CAD model representing the displacement of a point on the model boundary due to a perturbation of a CAD model parameter) with adjoint surface mesh sensitivities (which represent the derivative of a goal function with respect to surface mesh node position). A CAD-based design velocity computation method has been developed based on projection between discrete representations of perturbed geometries which can be linked to virtually any existing commercial CAD system. A key characteristic of the approach is that it can cope with the discontinuous changes in CAD model topology and face labelling that can occur under even small changes in CAD parameters. Use of the above approach allows computation of parametric sensitivities with respect to aerodynamic coefficients for native CAD parameters within feature-based commercial CAD modelling systems using adjoint data at a computational cost of just one adjoint analysis per objective function and one design velocity field evaluation per parameter. Gradient computation is demonstrated on test cases for an aerofoil model, a turbine blade model and a 3D wing model. Using these computed sensitivities enables the creation of a truly CAD-based aerodynamic optimisation system incorporating adjoint CFD data and using design velocities for computing geometric sensitivities and as input to a mesh deformation step. A prototype implementation of this system is presented and used to optimise a parametric CAD-based aerofoil model. In order to develop the approach further, future work should focus on resolving issues encountered when using design velocities for mesh deformation, extending the approach to more complex test cases, and potentially incorporating parametric effectiveness as a measure of the suitability of a given CAD parameterisation for optimisation purposes.

There is a requirement for better Integration between design and analysis tools, which is difficult due to their different objectives, separate data representations and workflows. Currently, substantial effort is required to produce a suitable analysis model from design geometry. Robust links are required between different analysis representations to enable analysis attributes to be transferred between distinct design and analysis packages for models at various levels of fidelity. This thesis describes a novel approach for Integrating design and analysis models by identifying and managing the relationships between the different representations. Three key technologies named Cellular Modelling, Virtual Topology and Equivalencing, have been employed to achieve effective simulation model management. Cellular representations are utilised to represent various decompositions of the design space based upon analysis requirements. Virtual Topology and Equivalencing are techniques utilised in this work for managing the relationships between various analysis representations where equivalent regions of space are linked to one another. These relationships can be exploited to automatically regenerate analysis models after updates and to transfer analysis attributes between equivalent analysis models. Prototype automated tools are introduced to demonstrate how multiple simulation models can be linked and maintained to achieve seamless Integration throughout the design cycle. These tools have been generated to interact with a number of distinct CAE packages to enable analysts to select their preferred tool for different analyses. It is shown how the prototype tools developed using the concepts in this thesis offer significant advantages for transferring analysis attributes between equivalent model representations in comparison to existing approaches.

The main aim of this work was to investigate the process-structure-property relationship of high density polyethylene (HOPE)/carbon nanofiller composites. A secondary aim was to develop thin thermoplastic films with enhanced electrical and mechanical properties for the potential use in aerospace applications. Three types of carbon nanofillers with different dimensions, multi-walled carbon nanotubes (MWCNTs), graphite nanoplatelets (GNPs) and carbon black (CB) respectively, were used to reinforce the polymer matrix. The melt-mixed HOPE/carbon nanofiller composites were processed by compression moulding, biaxial stretching and blown film extrusion, and the structure and properties of the resulting composites were characterised. The crystallinity and melting temperature of the material are barely influenced by the addition of carbon nanofillers, while the crystallization temperature is slightly increased due to a heterogeneous nucleation effect. The incorporation of carbon nanofillers has a positive effect on the modulus of the composites studied and a negative effect on the stress at break and strain at break. The relative effectiveness of generating rheological and conductive networks in the polymer is as follows: GNPs < CB < MWCNTs. The inclusion of carbon nanofillers led to significant strain hardening during the biaxial stretching of the material. The carbon nanofillers were further dispersed in the matrix by biaxial stretching. The mechanical properties of all the HOPE/carbon nanofiller composites were clearly improved after biaxial stretching. However, the volume resistivity of biaxially stretched HOPE/carbon nanofiller composites, at loadings lower than 4 wt%, was increased due to the deagglomeration of nanofillers and increased inter-particle distance. Blown films of the HOPE/MWCNT composites were manufactured at blow-up-ratios (BURs) of 2 to 3. The stress at break and strain at break of the composite films increases steadily with increasing BURs. Blown film extrusion also has a destructive effect on the conductive network of MWCNTs. However, there is no significant increase in the resistivity of the composite containing 8 wt% MWCNTs after film blowing at increasing BURs due to a sufficient density of nanotubes forming a robust conductive network .

This thesis presents an investigation into the failure of reinforced concrete beams without web reinforcement under the action of bending and shear. A total of 39 singly-reinforced concrete beams of various cross-sections were tested with two concentrated loads. The test specimens and the instrumentation were designed to yield detailed information on shrinkage strains, and the load-induced strains in concrete prior to and after the formation of diagonal tension cracks. The behaviour of the beams up to the failure load was carefully observed and studied. The mode of formation and propagation of cracks, and the failure surfaces were given special attention. The influence of bond between concrete and the tensile reinforcement and the contribution of the "dowel force" to shear resistance was considered. Quantitative analyses show that shear failure is not a bond failure and that the "dowel force" is a variable parameter which can assume any value including zero. From the analysis of the computed strains and the observed phenomena, a simple and rational expression is presented for the failure in shear of reinforced concrete beams subjected to concentrated loads. It is thought that the equation represents more accurately the behaviour of reinforced concrete beams under bending and shear than other available equations. The proposed equation was applied to other test data from different authors and the results are compared with the data obtained from this project. Errors inherent in the determination of diagonal cracking loads and the unreliable nature of visual observations are discussed. It is thought that this investigation and analysis will lead to a better understanding of the failure of reinforced concrete beam in shear, and therefore to a more rational basis for the design of web reinforcement. The nominal shear stress at the formation of diagonal cracks and at shear failure is compared with the permissible shear stress in beams without web reinforcement, recommended by the British and other Codes of Practice, It was observed that these permissible stresses which are currently in use are too low particularly for beams with shear-span to effective depth ratio of less than 3. It is therefore suggested that the nominal shear stress based on the external diagonal cracking reaction be considered as the permissible stress for beams without web reinforcement. This will ensure economy and safety even under the more severe loading conditions obtained in practice.