Three-dimensional fracture simulation is a big challenge to computational mechanics because of the complicated fracture surface geometry and the difficulty of characterising different failure and interaction mechanisms in complex three-dimensional stress fields. As an attempt to improve the ability of numerical methods to simulate discrete fractures in quasi-brittle materials, a three-dimensional fracture model is developed in the context of the combined finite-discrete element method. The proposed fracture model is capable of simulating the whole fracturing process for both tensile and shear fracture initiation and propagation, including pre-peak hardening deformation, post-peak strain softening, transition from continuum to discontinuum, and explicit interaction between discrete fracture surfaces. An adaptive remeshing algorithm is developed to simulate discrete fractures with less mesh dependency. This algorithm can accurately refine tetrahedral elements based on the local stress field, and update the local mesh as fractures propagate. As a further development of the fixed-mesh-based fracture model, it is incorporated into a two-way fluid-solid coupling model and it is successfully applied to simulate a hydraulic fracturing problem. A comprehensive numerical simulation is carried out by applying the proposed three-dimensional fracture model to investigate explicit fracture development and to evaluate the damage mechanisms of concrete armour units on breakwaters. Dolosse units are simulated in drop tests and pendulum tests. The dropping of an assembly of CORE-LOCTM units of prototype scale is simulated under an imaginary extreme loading condition. The whole structural response of the CORE-LOCTM units is accurately captured and the transient dynamic response including that by fracturing is explicitly characterised. To investigate fracture network formation and growth in multi-layered rock, two-dimensional and polyaxial deformation simulations are conducted. Three-dimensional stress heterogeneity caused by fracturing is accurately captured. The results show the three-dimensional fracture model is capable of generating realistic fracture patterns according to geomechanical principles of rock failure.

A two-tier study is presented in this thesis. The first involves the commissioning of an extant but at the time, unproven bubbling fluidised bed fast pyrolysis unit. The unit was designed for an intended nominal throughput of 300 g/h of biomass. The unit came complete with solids separation, pyrolysis vapour quenching and oil collection systems. Modifications were carried out on various sections of the system including the reactor heating, quenching and liquid collection systems. The modifications allowed for fast pyrolysis experiments to be carried out at the appropriate temperatures. Bio-oil was generated using conventional biomass feedstocks including Willow, beechwood, Pine and Miscanthus. Results from this phase of the research showed however, that although the rig was capable of processing biomass to bio-oil, it was characterised by low mass balance closures and recurrent operational problems. The problems included blockages, poor reactor hydrodynamics and reduced organic liquid yields. The less than optimal performance of individual sections, particularly the feed and reactor systems of the rig, culminated in a poor overall performance of the system. The second phase of this research involved the redesign of two key components of the unit. An alternative feeding system was commissioned for the unit. The feed system included an off the shelf gravimetric system for accurate metering and efficient delivery of biomass. Similarly, a new bubbling fluidised bed reactor with an intended nominal throughput of 500g/h of biomass was designed and constructed. The design leveraged on experience from the initial commissioning phase with proven kinetic and hydrodynamic studies. These units were commissioned as part of the optimisation phase of the study. Also as part of this study, two varieties each, of previously unreported feedstocks namely Jatropha curcas and Moringa olifiera oil seed press cakes were characterised to determine their suitability as feedstocks for liquid fuel production via fast pyrolysis. Consequently, the feedstocks were used for the production of pyrolysis liquids. The quality of the pyrolysis liquids from the feedstocks were then investigated via a number of analytical techniques. The oils from the press cakes showed high levels of stability and reduced pH values. The improvements to the design of the fast pyrolysis unit led to higher mass balance closures and increased organic liquid yields. The maximum liquid yield obtained from the press cakes was from African Jatropha press cake at 66 wt% on a dry basis.

Technical systems are critical drivers of economic consumption and production, and are generally accepted to be dependent on natural systems and processes throughout their life cycle. Accordingly, their sustainability is under increasing scrutiny. However, the basic constitution of sustainability of technical systems is unclear, and views on how sustainability can be assessed and improved are inconsistent. To address these issues, the research reported in this thesis developed two generic models of technical system sustainability: the Sustainability Cycle (S-Cycle), and the Sustainability Loop (S-Loop). The general elements and relationships involved in sustainability were identified through an inductive literature investigation spanning nine sectors. Sustainability was found to constitute an ability, which is in turn an emergent property of a system and manifested to humans as behaviour that maintains something. Activities were identified as the means by which materials and energy are transformed in a system. From a sustainability perspective, the behaviour of system activities was observed to involve the production of intended output, waste, and intended resources from inputs of renewable and non-renewable resources. This behaviour is formalised in the S-Cycle model. Humans seeking improved sustainability were found to interpret the behaviour of system activities to produce knowledge, and take action on the basis of this knowledge to produce effects that alter activity behaviour. This process is formalised in the S-Loop model, which positions the S-Cycle model within the context of human knowledge and interpretations. The validity, utility, and applicability of the S-Cycle model were evaluated through: two independent worked examples; three independent industrial case studies; two expert appraisal workshops with 27 practicing engineering designers; and an analytical study of 324 sustainability performance indicators (SPIs). Through these methods, the model was applied to ten distinct technical systems and expert opinions were elicited. All model elements and relationships were supported. One additional element/relationship was identified, leading to a refined model. The model was found to be artefact independent, supporting the identification of SPIs for different technical systems, and providing a consistent view on the behaviour of different sub-systems at various levels within a technical system. The S-Loop model received a degree of support through peer review and publication in the Journal of Environmental Management. Lastly, the research and findings were critiqued, leading to the identification of advantages, disadvantages, and recommendations, and areas for future research.

The goal of this research was to use weather parameters to compute refractivity variation of the atmosphere that can be used to predict refractivity distribution in the first kilometre of the atmosphere over the English Channel for UHF and VHF propagation and to understand the influence of meteorology on propagation. Different refractivity profiles are constructed based on meteorological data taken from the UK Meteorological Office in order to investigate their effects on wave propagation. The hourly experimental path loss between the transmitter and receiver obtained from the experimental setup comprising of two UHF and two VHF communication links are investigated for a period of one year. The experimental setup comprises of long and short trans-horizon paths (140 km and 50 km) having a transmitter located on Jersey and receivers on Portland and Alderney. In order to investigate the characteristics of refractivity and its impact on wave propagation, a propagation model is developed in MATLAB using parabolic equation method. The model is used to get an hourly modelled path loss corresponding to the experimental path loss for four communication links of UHF Portland, UHF Alderney, VHF Portland and VHF Alderney. The correlation between the modelled path loss and experimental path loss is presented for refractivity distribution recommended by the ITU and for that of a standard atmosphere. The simulated and experimental results showing the influence of evaporation duct upon path loss for frequencies of 240 and 2015 MHz is also included. The results obtained by using the standard atmospheric refractivity profile were a better fit to the experimental observations than the ITU recommended values for some of the investigated links. It is also inferred that evaporation ducts exist up to a height of 10 m for the short path at both frequencies and up to a height of 30 m for the long path at VHF but not at UHF.

Strontium titanate (SrTi03) is a perovskite material with diverse physical properties. Many of its properties are associated with its atomic structure, such as quantum paraelectricity, structural phase transitions, and extrinsically induced ferroelectricity. Accordingly, many structural investigations have been performed on bulk and thin film samples of SrTi03 . At the same time, many syntheses of SrTi03 nanoparticles and nanowires have been reported. Despite these factors, however, the structure and properties of SrTi03 nanoparticles and nanowires are not well understood. The aim of this thesis is to better understand such SrTi03 nanoparticles and nanomaterials using a combination of theoretical and experimental methods. Density-functional calculations were performed of bulk SrTi03 and (100) SrTi03 surfaces, with a focus towards nanomaterials applications. The outer layers of both SrO and Ti02 terminated (100) surfaces relaxed inward, and the subsequent layers alternately moved outwards and inwards. Furthermore, surface rumpling was observed. Both the interlayer distances and rumpling were determined as a function of depth. Tests of different exchange-correlation functionals were performed throughout. Next, the first-ever density-functional calculations were performed of the structural and electronic properties of SrTi03 nanowires. No ferroelectric states were found for the nanowires, despite active searching. Compressive axial and lateral strain was observed for all the nanowires, and the extent of this strain varied with diameter and surface termination. Furthermore, surface rumpling was found to occur on and within the nanowires; subsequent plots of the local polarization revealed that every nanowire possessed a radial polarization texture. Finally, electronic band structure calculations revealed that all the SrTi03 nanowires were metallic. Finally, experimental studies were performed on SrTi03 nanoparticles, with the longterm aim of determining and understanding their local atomic structure. Transmission electron microscopy showed that the nanoparticles were polydisperse, and powder x-ray diffraction measurements showed that they were composed of mostly SrTi03.

There is a growing need for ever more complex electronic systems as manufacturers aim to increase the functionality of their manufactured components. Direct write manufacturing is a technology that can provide a means to multi-functional components providing enhanced integration and automation in the manufacture of electronic systems An inkjet deposition system was used to fabricate electrical interconnects using dielectric and silver nanoparticie inks. To prevent thermal damage to the underlying substrate these inks were functionalised using localised post-process methods instead of conventional oven process routes. To improve on the electrical conduction of the printed components a localised electroplating system was devised. Durability of the printed components is essential to all applications. The inks were tailored to improve the robustness and were found to have passed preliminary aerospace durability and environmental testing. This direct write system was used to fabricate direct write electronics on an aerospace helmet shell. This was a proof-of-concept demonstrator and successfully shows that conformal electronic interconnects can be fabricated onto existing components.

Porous alumina anodized (PAA) membranes are widely used as templates for electrodeposition of conductive materials or directly as photonic material [1-3] due to the regular distribution of pores when anodized under defined temperature, electrolyte and voltage. This thesis investigated PAA nucleation and development under constant voltage in order to develop a periodic anodizing procedure to control pore diameter and interpore distance along the pore main axis. The periodic change in the geometrical parameters modifies the optical properties of the membranes and visible light interacts with the porous membrane when the periodicity of the structure is of the same order as the light wavelength. Two porous structures with reflectance peaks in the visible range were realized and their optical properties were studied. Branched membranes presented alternated layers of branched pore and main pore layers of controllable thicknesses. The reflectance spectra was modelled as a Bragg stack whose thicknesses and refractive indices of the alternating layers were obtained from ellipsometrical and SEM measurements of PAA membranes. The second structure was defined as necked membrane, as it presented periodic enlargements and restrictions of pore diameter along the pore main axis without branching. Reflectance spectra showed a single peak in the visible range whose position could be controlled by the anodizing temperature. Reflectance spectra showed by branched and necked samples were considered promising with regards to applications as interleaved reflectors in reflective displays. The presence of selective reflective layers interleaved in a stack display reduces light losses due to undesired absorbance of colour layers and more freedom in display design. [4] 1. Wang, B., et al., Preparation of photonic crystals made of air pores in anodic alumina. Nanotechnology, 2007. 18: p. 1. 2. Zheng, W.J., et al., Modulation of Transmission Spectra of Anodized Alumina Membrane Distributed Bragg Reflector by Controlling Anodization Temperature. Nanoscale Research Letters, 2009. 4(7): p. 665. 3. Zheng, W.J., et al., Distributed Bragg reflector made of anodic alumina membrane. Materials Letters, 2009. 63(8): p. 706. 4. Kitson, S., et al., Bright color reflective displays with interlayer reflectors. Optics Express, 2011. 19(16): p. 15404.

Nanomaterial metrology is fundamental to understanding the physical properties of nanomaterials and their environmental interactions. Particles, in the nano and sub-micrometer regimes, are attractive materials for use in biomedical applications such as drug delivery and medical imaging. In order to address concerns regarding their potential for cytotoxicity, particle characterisation before and after exposure to biologically relevant media is critical. Size is one of many particle properties that can influence their behaviour in biomedical applications, including their cellular uptake and circulation lifetime. Therefore, the sizing capabilities of three established (transmission electron microscopy (TEM), scanning mobility particle sizing (SMPS) and dynamic light scattering (DLS)) and three emerging particle sizing techniques (scanning ion occlusion sensing (SIOS), nanoparticle tracking analysis (NTA) and differential centrifugal sedimentation (DCS)) with Stober silica particles, 100 - 400 nm in diameter, as the test material, were evaluated. When exposed to biological media particles will spontaneously be coated with a film of biomolecules, predominantly proteins, which will subsequently define their biological identities. Being able to quantify and evaluate the composition of these so called "protein coronas" is key to understanding the bio-nano interface. In this study, the amount of immunoglobulin G (IgG) adsorbed onto gold particles, as a function of particle size and protein concentration, was measured, using a combination of techniques including DLS (and [Symbol appears here. To view, please open pdf attachment] -potential), NTA, DCS, and UV-Visible spectroscopy (UV-Vis) plasmonic sensing. [Symbol appears here. To view, please open pdf attachment] -potential was a good indicator of protein corona integrity, and deviations in the protein corona thicknesses measured by NTA and DCS at low protein coverage were observed. Finally, the surface chemistry of an electrospun polymer fibre scaffold was characterised using time of flight-secondary ion mass spectrometry (ToF-SIMS). The concentration of a cell adhesion enhancing peptide was measured to be linearly related to that in the bulk and its co-localisation with the polymers proven through imaging.

The huge growth in nanotechnology brings with it an increasing need for techniques capable of structural and chemical analysis on the nanoscale. Two such techniques are electron energy-loss spectroscopy in the scanning transmission electron microscope (STEM-EELS) and x-ray absorption spectroscopy in the scanning transmission x-ray microscope (STXM-XAS). Despite the different probe-specimen interactions of EELS and XAS, these techniques both excite transitions from core states into unoccupied excited states, providing remarkably similar chemical information, but with different spatial and spectral resolutions, as well as different electron/photon induced damage properties. Due to advances in the fabrication of diffractive x-ray optics, soft x-ray probes in the STXM can now achieve ~15 nm spatial resolution, while the STEM probe can routinely reach sub-nanometre dimensions. At the same time, the spectral performance of EELS is becoming more competitive with the ~0.1 eV resolutions of x-ray instruments, due to the development of monochromators in the electron microscope. While the spatial and spectral performances of these two techniques are continually converging, the gaps which still exist may be bridged by employing a correlative approach. The motivation of this thesis is to apply both STEM-EELS and STXM-XAS to a range of nanoscale systems, and to investigate the benefits and limitations of this correlative approach. In order to understand the biodegradation of carbon nanotubes (CNTs), spectral signatures corresponding to graphitic carbon have been used to map CNT aggregates within the cellular environment. The nature and distribution of functional groups on oxidised CNTs have also been characterised using EELS, and compared to XAS data from the literature. Lastly, wear debris generated from CoCr hip prostheses has been investigated within explanted tissue. For the first time, detailed chemical analysis was performed of debris particles, which were found to be composed of mainly oxidised Cr as well as trace amounts of oxidised Co. Additionally, some nanoparticles were observed to have metallic Co and Cr cores.

The development and utilisation of phthalocyanine (Pc) materials for practical applications has been subject of intense research due to their desirable optical, electrical, and recently discovered magnetic properties. Typically, in crystalline organic materials the charge transport, light absorption and magnetisation are anisotropic and strongly depend on structure, morphology and molecular orientation. Hence, an understanding of growth mechanism and controlled fabrication of thin films and nanostructures is essential for tailoring properties desirable for specific applications. e.g., for OFETs, crystalline thin films or one-dimensional nanostructures. Recently, vast advancement has been made in developing functional organic films including sublimation in (ultra) high vacuum using organic molecular beam deposition (OMBD). This environment can provide the essential material purity and structural reproducibility required in future high performance optoelectronic device applications, but is unfortunately costly. In this thesis, we introduce a lesser-known technique, organic vapour phase deposition (OVPD), operating at lower cost but still maintaining high purity. The morphology, crystallinity, spectroscopic characteristics and structure of copper phthalocyanine (CuPc) thin films and nanostructures have been investigated and their dependence on deposition conditions, i.e., substrate temperature and substrate type has been studied. We compare films obtained by OMBD and OVPD and find different morphological and structural changes; the surface morphology changes from granular to larger nano-fibrous and nano-whiskers with increasing substrate temperatures. In OMBD, the structure in a small proportion of the film changes from α-CuPc to β-CuPc at a substrate temperature of 200 oC. In the case of OVPD films, extensive study of the influence of parameters such as deposition pressure, deposition time and source to substrate distance is performed and variation in film morphology, texture, structural composition and molecular orientation is observed. We find that by successive growth of films produced by OMBD and OVPD, the molecular orientation can be controlled by the first “seed” layer. With further processing and optimisation, it is hoped that this could be used to create interpenetrating networks of different organic materials and optimal molecular orientation. We also demonstrate the fabrication using OVPD of high density CuPc nanowires with typical diameters between 10 - 100 nm, high directionality, and exceptional aspect ratios. We show that these nanowires are of a new crystal phase, named eta-CuPc. Lastly, OFETs fabricated with OMBD and OVPD grown CuPc thin films and nanowires are characterised. The current on/off ratio, mobilities and threshold voltage for thin films produced by the two methods are comparable and similar to what has been reported in literature. In contrast, OFETs with CuPc nanowires show remarkable improvement in turn-on voltage, while mobilities also seem to improve dramatically, although this is difficult to quantify. The challenges in growing CuPc nanowires directly on FETs with precise control of position and directionality are reviewed. The key issues that need to be resolved for future applications of these one-dimensional nanostructures are identified and are subject of on-going research. To conclude, this work has made important contribution in the efforts to develop, improve and enhance the deposition methods for fabricating functional thin films and nanostructures of CuPc material for use in organic electronic devices.