The hydrothermal synthesis (HS) of α-Fe2O3 nanorods (NRs) is investigated using a combination of complementary analytical techniques. The construction of an HS ‘process map’ as a function of temperature, time and phosphate (PO43-) concentration provides insight into the nature of intermediate β-FeOOH NR precipitation, dissolution and subsequent α-Fe2O3 growth, along with the effect of PO43- anion concentration on the development of α-Fe2O3 particle shape. An HS processing temperature of 200˚C and an Fe3+ : PO43- molar ratio of 31.5 yielded crystalline acicular α-Fe2O3 NRs with an aspect ratio of ~ 7 (~ 420 nm long, ~ 60 nm wide). The additional effects of FeCl3 concentration, pH, stage of phosphate addition and α-Fe2O3 seed content on the growth of α-Fe2O3 NRs is investigated. The development of a novel valve-assisted pressure autoclave is described, facilitating the rapid quenching of hydrothermal suspensions into liquid nitrogen, providing ‘snapshots’ closely representative of the in situ physical state of the synthesis reaction products. Examination of the samples acquired as a function of reaction time and known reaction temperature provides fundamental insight into the anisotropic crystal growth mechanism of the acicular α-Fe2O3 NRs. It is considered that the release of Fe3+ ions back into solution through intermediate β-FeOOH dissolution supplies the nucleation and growth of primary α-Fe2O3 nanoparticles (NPs) (< 10 nm) which subsequently coalescence through a mechanism of oriented attachment (OA) with increasing temperature, into larger, acicular α-Fe2O3 NRs. Fourier transform infra-red spectroscopy investigation of the quenched reaction products provides evidence for PO43- absorption on the α-Fe2O3 NPs, in the form of mono or bi-dentate (bridging) surface complexes, on surfaces normal and parallel to the crystallographic α-Fe2O3 c-axis, respectively. The balance between bi-dentate and mono-dentate phosphate absorption is considered to be critical in mediating the acicular shape of the α-Fe2O3 NRs. A feasibility study on the incorporation of ferromagnetic cobalt, Co3O¬4 NPs or CoFe2O4 NPs into α-Fe2O3 NRs during HS is presented. In all cases, there is no evidence for the incorporation of cobalt within the α-Fe2O3 NRs or the formation of hetero-nanostructures with the Co3O4 or CoFe2O4 NPs. The overall growth mechanism of single crystalline acicular α-Fe2O3 NRs involves the anisotropic growth and dissolution of intermediate β-FeOOH NRs, governed by its crystallographic structure, and the OA of primary α-Fe2O3 NPs, mediated by the preferential absorption of phosphate surfactant.

A granular material is usually an irregular packing of particles and its constitutive relationship is very complex. Previous researches have shown that the discrete element method is an effective tool for fundamental research of the behaviour of granular materials. In this research, discrete element modelling was used to obtain the macroscopic stress-strain behaviour of granular material in cavity expansion. The micro mechanical features and the mechanical behaviour of granular material at particle level have been investigated. A simple procedure was used to generate the samples with spherical particles and two-ball clumps. The influence of particle properties on the stress strain behaviour within an aggregate was investigated in biaxial test simulations. It was found that more angular clumps lead to sample more homogeneous and that the interlocking provided by the angular clumps induces a higher strength and dilation in the sample response. Interparticle friction was also found to have significant effect on the strength and dilation of the sample. The sample macromechanical properties can be obtained from these biaxial simulations. For investigating the effect of particle shape, the spherical or non-spherical(two-ball clump) particle shapes were used in the cavity expansion simulations. Monotonic loading was performed on a fan-shaped sample with various particle properties under a range of initial cavity pressures. The results were compared with calculated analytical solutions and existing experimental data in order to optimise the micro mechanical parameters governing the behaviour. The pressuremeter test data were adapted for this comparison since the theory of cavity expansion has been used to describe the pressuremeter tests in soil and rocks by many geotechnical researchers and engineers. This research showed that particle properties play an important role in soil behaviour of cavity expansion under monotonic loading. The contribution of this research is to present that it is possible to model a granular material of boundary value problem (cavity expansion) under static conditions, providing micro mechanical insight into the behaviour.

The dumping cost of wasted concrete including the rejected units in precast concrete plants is expected to keep rising as the production increases. The waste material from precast concrete hollow core floors (hcu) is high grade and uncontaminated material. This research work was carried out to investigate mainly the strength and other engineering properties of high strength concrete made with recycled concrete aggregate derived from rejected hcu. Three major categories (based on a questionnaire) were investigated: (i) Type of crushers and the crushing method, (ii) The properties of RCA output from these crushers, (iii) The performance of fresh and hardened concrete, including prestressed concrete, with these RCA. The input material for the crushers was from the same origin of disposed hcu's. The waste concrete was crushed to -14 mm using three different types of crushers - the cone, impact and jaw crushers. The recycled material was separated into fractions of 14 mm, 10 mm and - 5 mm, and tested for physical and mechanical properties relevant to use in concrete. Concrete was then made using zero (control mix), 20% and 50% replacement of recycled coarse (RCCA), recycled fine (RCFA) and mixed (RCCA+RCFA) aggregates. All three crushers produced acceptable shape and strength of RCCA. Some properties are competitive to that of natural limestone aggregate. RCFA was much coarser than river gravel and just complied with the British Standard coarse grading limits. The impact crusher performed best with regard to most aggregate properties, e. g. flakiness, strength and water absorption, but has a disadvantage in producing a large amount of fine-to-coarse RCA. Concerning shape and strength, RCA showed similar properties, and in some cases better, than the conventional limestone aggregate. The water absorption for RCA is 3 to 4 times greater than the natural aggregates. For that reason an extra amount of water (called free water) will be added to the mix to compensate the water absorptions for aggregates. Some proportions of this extra added water may not be absorbed by the aggregates and will float to interrupt the design W/C ratio and caused it to increase. The slump value of fresh concrete made with RCA varied widely depending on the percentage and type of replacement, and the type of crusher. The compaction factor of fresh concrete made with RCA was more consistent and logical. Compressive strength of concrete made with RCA were generally within ±5 N/mm2 of the control. For tensile strength, RCA showed similar performance to that of natural limestone. The SS density of concrete with RCA is lower than that of the control concrete and is lower if the replacement percentages increase. Using RCFA causes higher bleeding rate and considerably reduces density and strength, and the severity increases as the replacements of RCFA increases. Using natural limestone aggregates with RCFA will minimize this poor behaviour and maintain the strength to certain extent. However joining RCCA with RCFA will not limit the poor behaviour and is not recommended. For bonding reinforcing bars most methods indicated that high replacement (100%) of CA cause some reduction in bond strength. In pretensioning wires the RCA concrete had a better performance in bond but some reduction was still reported. Prestressed X-shape beams were used to assess the effects of using of RCA on the performance of hollow core slabs. For 20% RCCA replacements, the prestressing loss, deflection and X-beam flexure crack failure were similar to the standard X-beam, at least and within the design limit. However at higher replacements (50%) some deterioration starts to reveal and the effects are even greater when using a combination of RCCA and RCFA.

Laser Doppler blood flow imaging is well established as a tool for clinical research. The technique has considerable potential as an aid to diagnosis and as a treatment aid in a number of situations. However, to make widespread clinical use of a blood flow imager feasible a number of refinements are required to make the device easy to use, accurate and safe. Existing LDBF systems consist of 2D imaging systems, and single point scanning systems. 2D imaging systems can offer fast image acquisition time, and hence high frame rate. However, these require high laser power to illuminate the entire target area with sufficient power. Single point scanning systems allow lower laser power to be used, but building up an image of flow in skin requires mechanical scanning of the laser, which results in a high image acquisition time, making the system awkward to use. A new approach developed here involves scanning a line along a target, and imaging the line with a 1D sensor array. This means that only one axis of mechanical scanning is required, reducing the scanning speed, and the laser power is vastly reduced from that required for a 2D system. This approach lends itself well to the use of integrated CMOS detectors, as the smaller pixel number means that a linear sensor array can be implemented on an IC which has integrated processing while keeping overall IC size, and hence cost, lower than equivalent 2D imaging systems. A number of front-end and processing circuits are investigated in terms of their suitability for this application. This is done by simulating a range of possible designs, including several logarithmic pixels, active pixel sensors and opamp-based linear front-ends. Where possible previously fabricated ICs using similar sensors were tested in a laser Doppler flowmetry system to verify simulation results. A first prototype IC (known as BVIPS1) implements a 64x1 array of buffered logarithmic pixels, chosen for their combination of sufficient gain and bandwidth and compact size. The IC makes use of the space available to include two front-end circuits per pixel, allowing other circuits to be prototyped. This allows a linear front-end based on opamps to be tested. It is found that both designs can detect changes in blood flow despite significant discrepancies between simulated and measured IC performance. However, the signal-noise ratio for flux readings is high, and the logarithmic pixel array suffers from high fixed pattern noise, and noise and distortion that makes vein location impossible. A second prototype IC (BVIPS2) consists of dual 64x1 arrays, and integrated processing. The sensor arrays are a logarithmic array, which addresses the problems of the first IC and uses alternative, individually selectable front-ends for each pixel to reduce fixed-pattern noise, and an array of opamp-based linear detectors. Simulation and initial testing is performed to show that this design operates as intended, and partially overcomes the problems found on the previous IC - the IC shows reduced fixed pattern noise and better spatial detection of blood flow changes, although there is still significant noise.

Concrete filled steel tubular (CFT) columns can employ the advantages of both materials: steel and concrete. Connection to such columns, however, is problematic. This is especially so if the required connection is both bolted and moment-resisting. To address this issue, a novel blind-bolted and moment-resisting connection to CFT column has been developed. This connection uses an innovative blind-bolt, introduced in previous research at the University of Nottingham and is termed the Extended Hollobolt (EHB). The EHB has been developed to provide sufficient tensile resistance and stiffness for the connection to develop resistance to moment. Previous research work has studied the performance of this connection under monotonic loading. The performance of such connection under cyclic loading, however, is not yet investigated. The work presented in this thesis addresses this gap in knowledge. This thesis reports on a series of full scale testing of joints consisting of beam endplates connected to CFT columns using this blind bolt. The test connections were constructed with relatively thick endplate so as to isolate the CFT column and the blind bolt as the relatively weak elements in the connection system. This study focuses on the behaviour of the connections with principal failure modes attributed by the blind bolt and the CFT column. The experiments were conducted to obtain insights into the hysteretic moment-rotation relationship, available ductility & energy dissipation capacity, observe typical failure modes, and develop relevant understandings of the Extended Hollobolt-endplate connection subjected to cyclic loading. The selected connection details were chosen to examine the influential parameters of the joint hysteretic moment-rotation behaviour. From the experimental results, two representative failure modes, bolt fracture and column face bending failure, were observed and categorized in relation to the connection configuration. The connection behaviour are described and compared with respect to the influences of bolt grade, cyclic loading procedure, tube wall thickness and concrete grade. Based on the experimental hysteretic moment-rotation relationships, an evaluation of the cyclic characteristics and an analysis' of the cumulative damage were carried out for the two representative connection categories. The joint hysteretic moment-rotation response was assessed in term of degradations of strength, stiffness, ductility, and energy dissipation. The use of damage levels and stages in the interpretation of damage evolutions for the connection behaviour is also described in this thesis. The findings of cumulative damage analysis suggest that the energy based cumulative damage index outweighs the other indices in characterizing the progressive damage process of the connections in this study. This is especially the case for those related to hysteresis loops at repeated cycles of each loading amplitude. Following the experimental study, 3D nonlinear finite element models of the connections were developed to analyse the mechanical response of the connection. The comparison of the numerical and experimental moment-rotation envelope curve is discussed with respect to related geometric and material parameters. The connection failure modes and displacement distributions were further examined as a supplement to the experimental findings that were necessarily limited by instrumentations. This work also presents mathematical models for the hysteretic moment-rotation relationships simulating the loading, unloading and reloading segments of the hysteresis loops. Characterizing parameters were introduced to, allow for the softening slope, linear segment slope, and degradations of strength and energy dissipation. This study concluded that the proposed finite element model simulates well the behaviour of the connection with good prediction of the moment-rotation envelope curves and of the failure mode. It is also concluded that the proposed mathematical models define well the non-linear loading and unloading paths with reasonable accuracy. It is finally claimed that the Extended-Hollobolt endplate connection provides a stable improvement in strength and stiffness under cyclic loading compared with other similar connections.

Air plasma sprayed thermal barrier coating (APS TBC) systems are usually applied to engine components to reduce the temperature of the substrate and increase the efficiency of engines. However, failure of these coatings leads to oxidation and corrosion of the substrate. Therefore, a thorough understanding of the coating failure is necessary to predict the lifetime of coated components. This project has carried out stress analysis and prediction of subsequent failure of APS TBC systems associated with sintering of the TBC, oxidation of the bond coat (BC), substrate geometry, undulations at the coating interfaces and coating fracture toughness. Stress analysis is crucial for predicting TBC failure as stresses in the vicinity of the coating interfaces cause cracks and subsequent coating delamination. The Finite element (FE) method was used for stress analysis of TBC systems at high temperature stage and at cooling stage after operation. Initially, FE model of an axisymmetric unit cell representing the slice of a coated cylinder was used. Different radii for cylinders were used to investigate the significance of substrate curvature on coating stresses. The effect of asperities at the coating interface on residual stresses was observed using 3D models. The models were built based on the actual geometries of asperities, which were extracted from 3D SEM images of the coating interfaces. An Arrhenius approach was utilised to implement changes in mechanical and physical properties of TBC due to sintering. BC oxidation and related changes in its composition were also implemented. The accuracy of assumptions for FE models was validated by comparing the evaluated stresses against experimental results by project partners. Finally, the effects of stresses and fracture toughness of the coatings and coating interfaces on failure of the TBC system were studied, using cohesive surface modelling and extended finite element modelling (XFEM) methods.

This thesis details the synthesis and characterisation of novel nanocomposite materials. The unifying theme of all the projects investigated, is the aim to combine metal or metal oxide nanoparticles with polymer systems. In order to investigate the structure of the materials produced, the extensive use of advanced electron microscopy techniques is essential throughout. Chapter 1: This introductory chapter outlines key themes that are relevant to all the areas of research in this thesis. Theory, background and applications are provided for the fields of nanoparticles, polymers, and supercritical fluids. Chapters 2, 3 and 4 each report a separate area of research. In each chapter additional theory and background is provided where appropriate, and previous literature is discussed. The aims, results and discussion of each research area are contained within the relevant chapter, as well as conclusions and future work. Chapter 2: Supercritical CO2 is used to impregnate optical polymer substrates with silver complexes, which are then decomposed to form nanoparticles. Chapter 3: Metal oxide nanoparticles are used to stabilise dispersion and suspension polymerisations, providing a method of recovering nanoparticles from aqueous solutions and embedding them on the surface of polymer powders. Chapter 4: Two alternative routes, for creating polymer microspheres surface decorated with silver nanoparticles, are compared. Chapter 5: A detailed description of the synthetic methods, equipment, and analysis techniques used in this research is provided. Chapter 6: A brief but overall conclusion to the research is given.

Vacuum infusion technology, even though first reported more than 50 years ago, was not popular for mainstream fibre reinforced polymer composites manufacturing until recently. Its present-day popularity is due to the increasing emphasis on the manufacturing cost as well as environmental and health concerns. As a result, novel processes such as Vacuum Infusion (VI) and Seemans' Composite Resin Injection Moulding Process (SCRIMPTM), employing the same basic technology, have been developed. As latecomers, these processes have not been investigated in detail and there exists a lack of understanding that can undermine the potential improvements in composites manufacturing offered by them. The present work is focused on (i) enhancing the fundamental understanding, and (ii) advancing the processing technology to fully exploit their potential. Limitations of the existing analytical models for fluid flow in VI are explored. Then, improvising upon and extending these models, analytical formulations for the pressure profile and fill-times in rectilinear and radial flow VI processes are developed. An important result from this study is that with increasing reinforcement compliance, the analytical VI pressure profile diverges from the RTM pressure profile. It is found that for rectilinear as well as radial flow processes, the fill-time ratio between equivalent RTM and VI remains constant. Experimental validation for these formulations show that the pressure profile varies with flow progression in both rectilinear and radial flow VI. This leads to a dynamically changing fill-times ratio between RTM and VI. This dynamic behaviour, which is contrary to analytical predictions, is explained by hypothesising that the compliance characterisation experiments do not replicate the actual events in VI. The issue of process control is also investigated for the VI process. A novel approach, using non-intrusive sensors and real-time flow simulations, is designed and implemented. The study gives important insights about the controllability of this process. It is found that in VI, due to low driving pressure, an optimum window of opportunity exists for process control. Reinforcements with high permeability give higher flow velocity, while low permeability reinforcements lead to lower flow velocity. Both of these cases lead to a marginal window of opportunity and poor process controllability. For reinforcements that offer good controllability, the control system is able to identify flow deviations and correct them, increasing the process efficiency.

The overall objective of this study was to develop and validate a predictive modelling methodology for simulating the static and dynamic impact failure response of thermoplastic composite sandwich structures. The work has primarily focused on sandwich constructions with commingled woven fabric glass/polypropylene composite skins and a crushable polypropylene foam core. The static and high strain rate mechanical properties of the thermoplastic composite skin material have been experimentally characterised. This investigation showed that the tensile and compressive modulus and strength increased with strain rate while the shear modulus and strength decreased as strain rate increased. A modelling methodology was developed for predicting damage in the thermoplastic composite using the advanced MAT 162 material model that is implemented in the LS-DYNA explicit finite element code. An inverse modelling technique for calibrating and validating the MAT 162 damage parameters was developed. The material model was validated for predictive simulation of the static and crash response of a large scale complex shaped demonstrator thermoplastic composite automotive component. The static and dynamic mechanical properties of the thermoplastic foam core have been experimentally investigated and presented. This was followed by an experimental investigation and finite element modelling of the failure modes of the thermoplastic composite sandwich under static and dynamic localised indentation and bending loads. A fracture criteria was implemented in the model to simulate core shear fracture. The main contributions to knowledge from this doctoral study are: the static and dynamic characterisation of the mechanical properties and failure modes of the thermoplastic composite and the crushable thermoplastic foam material; development of a validated modelling methodology for predicting damage in thermoplastic composites; and development of a finite element modelling procedure for simulating the static and dynamic impact failure behaviour of thermoplastic composite sandwich structures.

Piled embankments provide an economic and effective solution to the problem of constructing embankments over soft soils. This method can reduce settlements, construction time and cost. The performance of piled embankments relies upon the ability of the granular embankment material to arch over the ‘gaps’ between the pile caps. Geogrid or geotextile reinforcement at the base of the embankment is often used to promote this action, although its role in this respect is not completely understood. Design methods which are routinely used in the UK (e.g. BS8006, 1995; Hewlett & Randolph, 1988; the ‘Guido’ method, 1987) estimate the stress which acts on the underlying soft ground completely independently of the properties of the soft ground. This stress is then generally used to design the amount of geogrid or geotextile reinforcement required. However, estimation of this load can vary quite considerably for the various methods. Using finite element modelling the 2D and 3D arching mechanisms in the embankment granular fill has been studied. The results show that the ratio of the embankment height to the centre-to-centre pile spacing is a key parameter, and generic understanding of variation of the behaviour with embankment height has been improved. These analyses are then extended to include single and multiple layers of reinforcement to establish the amount of vertical load which is carried and the resulting tension, both in 2D and 3D. The contribution to equilibrium of the subsoil beneath the embankment is also considered. Finally the concept of an interaction diagram (and corresponding equation) for use in design is advanced based on the findings.