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Aluminium matrix syntactic foams (AMSFs) are composite materials consisting of hollow ceramic microspheres (CMs) embedded in a metal matrix. They have higher specific stiffness, specific strength and energy absorption capacity than metal foams or polymeric syntactic foams. They are promising candidate materials for energy absorption applications, e.g. crash protection, packing materials and damping panels. The present study focuses on the fabrication of AMSFs and characterisation of their mechanical properties under static and dynamic loading. CMs with three different particle size ranges, large - 250-500 μm, medium - 125-250 μm and small - 70-125 μm, were used. Three types of AMSFs were fabricated: uniform, layered and mixed structures. Uniform AMSFs contain large, medium or small CMs alone. Double-CM layered AMSFs contain half each of large and small CMs, and have six layer structures. Triple-CM layered AMSFs contain one third each of large, medium and small CMs, and have three different layer structures. Fully mixed AMSFs contain a single layer of fully mixed large and small CMs, and have three different proportions. Partly mixed AMSFs contain several layers of fully mixed large and small CMs, with different proportions. All AMSFs exhibited homogeneous microstructures in each layer or the whole sample with uniformly distributed CMs in the Al matrix. Static compression tests were conducted on the AMSFs. The compressive strength of uniform AMSFs increased with decreasing CM size. The results show that the compressive strength of layered AMSFs increased with increasing number of layers and reducing layer thickness. Layer order had no effect on compressive strength, with soft layers failing before strong layers regardless the relative layer locations. The compressive behaviour of mixed AMSFs was similar to uniform AMSFs, with the compressive strength higher than the average strength of the uniform AMSFs containing the same constituent CMs. Low speed impact tests were performed on the AMSFs. Three failure modes, ductile, brittle and ductile-brittle, were observed. Uniform AMSFs with smaller CMs and layered AMSFs with more layers had higher peak stresses. Mixed AMSFs had a higher peak stress than the average of peak stresses of their constituent layers, while layered AMSFs had a lower peak stress than the average of peak stresses of their constituent layers. Layered AMSFs showed better ductility than uniform and mixed AMSFs. The ductility of AMSFs decreased with increasing impact energy. Both peak stress and energy absorption were found to increase with impact energy, but not significantly affected by impact momentum. The energy absorption capacity of the different types of syntactic foams was compared. The energy absorption was mainly determined by the type of CMs in the AMSFs and was less affected by the structure. Uniform AMSFs with smaller CMs and layered AMSFs with more layers had higher energy absorption. Mixed AMSFs had higher energy absorption than the average of the uniform AMSFs containing the same constituent CMs. An analytical model has been developed to simulate the stress and strain evolutions in ASMFs under impact loading. Impact loading generates an elastic wave and a plastic wave at the top of specimen. The elastic wave turns into a plastic wave when it bounces back at the bottom of the specimen. The two plastic waves then propagate inside the specimen with the same speed but opposite directions. The analytical model captures the key characteristics of stress fluctuation during impact. Both the inertia stress, caused by movement of particles in the specimen, and the contact stress, caused by momentum loss of impactor, can also be calculated by the analytical model. Experimental stress was caused by momentum loss of impactor. Theoretical predictions of evolutions of the base stress, which is the sum of inertia stress and contact stress, and the strain during impact agreed well with the experimental results.

A systematic and detailed design, building and testing of a high-sensitivity real-time magnetovision imaging system for non-destructive testing (NDT) was the purpose of the research presented here. The magnetic imaging systems developed were all based on an ultra-high sensitivity Quantum Well Hall Effect (QWHE) sensors, denoted as the P2A, which is based on GaAs-InGaAs-AlGaAs 2DEG heterostructures. The research progressed from 0D (single sensor) to 1D (linear array) to 2D (two dimensional arrays) testing modalities. Firstly, the measurement of thermal and shot noises, drift, detection limit, and dynamic offset cancellation of the QWHE sensor were studied in detail to set the framework and limitations of the fundamental QWHE sensors before their eventual use in the imaging systems developed subsequently. The results indicate that the measured data agrees well with calculations for thermal and shot noise when the input bias current is < 3 mA. The measured drift voltages of various QWHE sensors (P2A and P3A) are less than 200 µV when the sensor bias voltage is less than or equal to 2 V. A 4-direction dynamic offset cancellation technique was developed and the results show that the offset equivalent magnetic field of the QWHE sensors can be reduced from ~ 1mT to readings equal to the Earth magnetic field (~ 50 µT). Secondly, a flexible 16 × 1 array and a 32 × 2 staggered array magnetic-field scanners were designed, built, and tested. The QWHE magnetometer had a field strength resolution of 100 nT, and a measurement dynamic range of 138 dB. The flexible 16 × 1 magnetic field scanner can be used to test uneven and/or curved surfaces. This gives the flexible magnetic field scanner better inspection capabilities in both welding hump and circular pipe samples. By the staggered arrangement of two sensor arrays, a 15.4 point per inch horizontal spatial resolution can be achieved for the staggered 32 × 2 magnetic field scanner. Both direct and alternating magnetic flux leakage (DC and AC MFL) tests with the QWHE magnetometer were accomplished to obtain graphical 2-dimensional magnetic field distributions. Both the shape and the location of defects can be identified. The results show that the sensor has high sensitivity and linearity in a wide frequency range which makes it an optimum choice for AC-MFL testing and both ferromagnetic and non-ferromagnetic materials can be investigated. Thirdly, real-time 8 × 8 and 16  16 QWHE array magnetic-field cameras were designed, built, and tested. These prototypes can measure static magnetic field strengths in a 2-dimensional plane. Different shapes of magnets and magnetic field polarities can all be identified by the 8 × 8 magnetic field camera. The camera has a resolution of 3.05 mT, and a dynamic range of 66 dB (the minimum and maximum fields measurable are 3.05 mT and 6.25 mT) and a real time magnetic field measurement rate of 13 frames per second (FPS). By contrast the1616 array magnetic field camera has an improved sampling rate of 600 frame per second and with the use of an interpolation technique, a spatial resolution of 40.6 point per inch can be achieved. The minimum and maximum detectable magnetic field for this magnetic field camera are 1.8 µT and 29.5 mT respectively leading to a record dynamic range of 84 dB for high quality imaging. Finally, a novel, hand held, magnetovision system based on the real-time 16 × 16 QWHE array magnetic-field camera was developed for improved DC and AC electromagnetic NDT testing. The system uses a new super heterodyne technique for data acquisition using the QWHE sensor as a multiplier. This is the first report of such a technique in Hall effect magnetometry. The experimental results of five case studies demonstrate that the defects location and shape can be successfully measured with MFL in DC and AC magnetic field configurations including depth profiling. The major advantages of this real-time magnetic-field camera are: (1) its ease to use as a MFL testing equipment in both DC and AC NDT testing, (2) its ability to provide 2D graphical images similar to Magnetic Particle Inspection (MPI) but without its inherent health and safety drawbacks, (3) its capability to test both ferromagnetic and non-ferromagnetic materials for deep defects below the surface using low frequency alternating magnetic fields, and (4) its ability to identify materials (metals) by alternating external magnetic field illuminations, which has considerable potential in several applications such as security checking and labelling, magnetic markers for analysis, bio-imaging detection, and medical treatments amongst others.

Plasma electrolytic oxidation (PEO) is a relatively novel surface modification technique that provides excellent wear- and corrosion-resistant coatings on light-weight metals, in particular on aluminium. Formation of PEO coatings involves complex processes and mechanisms that are difficult to study. In this work, a new method of in-situ impedance spectroscopy is used to provide new insights into fundamental characteristics of PEO processes and coating formation mechanisms as well as to develop new means of process control. This method is based on application of a variable frequency voltage perturbation signal to obtain impedance characteristics of the electrolyser during the PEO processing. The applied voltage signal and the current response are collected and post-processed to verify the system linearity, refine phase, reduce noise and spline the impedance spectra. The obtained spectra are then fitted with appropriate equivalent circuits to reveal mechanisms underlying the PEO process. Physical meaning of various circuit components is verified using specially designed experiments in which certain system characteristics are set up in such way to obtain controllable processing conditions, such as electric field distribution in the electrolyser, electrolyte resistance or coating thickness. The circuit analysis reveals specific RC and RL loops that can be related to individual processes associated with interfacial charge transfer and transport phenomena. Characteristic time constants corresponding to these processes are evaluated and their evolution with PEO treatment time is considered. Correlations of the process kinetics with phenomena observed during the PEO treatment of Al and coating growth characteristics are discussed. Several experiments involving complimentary methods and devices are also designed and carried out to assist the main method in investigation of the PEO processes. COMSOL Multiphisics software package is used for modelling the distribution of electric field and electrolyte resistance in the electrolyser; ex-situ EIS analysis- for impedance spectra comparison with ISIS results; fractal analysis- for studying the effects of coating morphology on impedance spectra; specialized imaging multi-channel (SIM) framing camera- for real-time observation of discharge events; and FFT analysis of high-resolution current signals- for studying the information on individual discharge events. Based on these studies, the characteristics of PEO process are discussed from different aspects and these better understanding is eventually achieved.

Calcium/calmodulin-dependent serine protein kinase (CASK) is a membrane-associated guanylate kinase (MAGUK) family protein, which is encoded by a gene of identical name present on the X chromosome. CASK may participate in presynaptic scaffolding, gene expression regulation, and cell junction formation. CASK is essential for survival in mammals. Heterozygous mutations in the CASK gene (in females) produce X-linked intellectual disability (XLID) and mental retardation and microcephaly with pontine and cerebellar hypoplasia (MICPCH, OMIM# 300749). CASK mutations are also frequently associated with optic nerve hypoplasia (ONH) which is the most common cause of childhood blindness in developed countries. Some patients with mutations in CASK have been also diagnosed with optic nerve atrophy (ONA) and glaucoma. We have used floxed CASK (CASKfloxed), CASK heterozygous knockout (CASK(+/-)), CASK neuronal knockout (CASKNKO) and tamoxifen inducible CASK knockout (CASKiKO) mouse models to investigate the mechanism and pathology of CASK-linked ONH. Our observations indicate that ONH occurs with 100% penetrance in CASK(+/-) mice, which also displayed microcephaly and disproportionate cerebellar hypoplasia. Further, we found that CASK-linked ONH is a complex developmental neuropathology with some degenerative components. Cellular pathologies include loss of retinal ganglion cells (RGC), astrogliosis, axonopathy, and synaptopathy. The onset of ONH is late in development, observed only around the early postnatal stage in mice reaching the plateau phase by three weeks of birth. The developmental nature of the disorder is confirmed by deleting CASK after maturity since CASKiKO mice did not produce any obvious optic nerve pathology. Strikingly the CASKfloxed mice expressing ~49% level of CASK did not manifest ONH despite displaying a slightly smaller brain and cerebellar hypoplasia indicating that ONH may not simply be an extension of microcephaly. We discovered that deleting CASK in neurons produced lethality before the onset of adulthood. The CASKNKO mice exhibited delayed myelination of the optic nerve. Overall this work suggests that CASK is critical for neuronal maturation and CASK-linked ONH is a pervasive developmental disorder of the subcortical visual pathway. Finally, in a side project, I also described a new methodology of targeting neurons using receptor-mediated endocytosis which would help target retinal neurons for therapeutic purposes in the future.

Abstract: The development of more environmentally-friendly and cost-effective extraction and production technologies is a key to sustaining heavy oil and bitumen production. The high viscosity of the heavily degraded petroleum requires additional processing in order to recover such challenging resources from both shallow surface deposits and deeper underground deposits. Intensive processing conditions require substantially more energy while the degraded nature of the heavy crude and bitumen leads to a lower price. The extraction involves numerous processes that separate valuable hydrocarbons from water and solids. Complete separation of heavy oil (bitumen) is not typically possible, due to the complexity of the bituminous (oil) sand ore. As a result, multiphase waste streams are generated at each step, which require a special treatment and/or complex disposal protocols. The dispersed nature of the waste makes its management difficult and expensive. Preparing specially designed composite particles by combining the properties of different materials may provide an effective method for such challenging tasks, by taking advantage of desirable and supressing undesirable properties. Responsive behaviour can be incorporated into the composite particle to prepare smart materials tailored to the specific applications. To this end, various types of responsive particles were prepared and tested in this thesis research, including: 1. Particles with Switchable Wettability. Particles with switchable wettability were prepared from silica by chemical functionalization of its surface with CO2-switchable amidine moieties. The surface of switchable particles, under CO2, is more hydrophilic due to the ionized surface groups while, in the absence of CO2, it is less hydrophilic as surface group revert back to their basic non-ionic state. Both switchable oil-in-water and water-in-oil emulsions were thus stabilized/destabilized using solid particles with switchable and tunable wettability. 2. Responsive Absorbent Particles. Changes to the surface properties of particles can induce changes to colloidal stability. Composite absorbent particles consisting of an absorbent core coated by an interfacially active material were prepared by emulsion droplet dehydration of specially formulated emulsions. The composite absorbent particles with initial intermediate wettability were effectively dispersed in non-aqueous environment such as oil-continuous emulsions (e.g., bitumen emulsions) and attached to emulsified water droplets. The surface of the composite absorbent particles became more hydrophilic and formed large aggregates following absorption of water. Large aggregates of spent absorbent particles were much easier to separate. 3. Interfacially active Magnetic Particles. Interfacially active particles were prepared by sequential adsorption of different cellulosic materials onto magnetic iron oxide (Fe3O4) particles. Interfacially active magnetic particles were effectively attached to the oil-water interface and imparted magnetic susceptibility to the biphasic mixture. Adding such interfacially active magnetic particles to biphasic waste (e.g., emulsion droplets, rag layers and sludge) allowed biphasic waste to be magnetically separated. The ability to induce a response in the properties or function (e.g., emulsion or colloidal stability) of a particle can result in smarter processes that are specifically designed to take advantages of changing process conditions. Alternatively, manipulation and separation of responsive (i.e., magnetic) particles can be facilitated by applying an external force (i.e., a magnetic field). By matching a process with an appropriate responsive particle, it is possible to design processes with reduced operating cost, less waste, and fewer environmental and health risks. Specifically, different responsive composite particles were designed and prepared to dewater bitumen emulsions by absorption and enable magnetic separation of emulsions droplets, rag layer and sludge.

This dissertation presents a one-dimensional thermomechanical constitutive model for shape memory alloys based on basic concepts of thermodynamics and phase transformation kinetics. Compared with other developed constitutive relations, this thermomechanical constitutive relation not only reflects the physical essence of shape memory alloys, i.e., the martensitic phase transformation involved, but also provides an easy-to-use design tool for engineers. It can predict and describe the behavior of SMA quantitatively. A multi-dimensional constitutive relation for shape memory alloys is further developed based on the one-dimensional model. It can be used to study the mechanical behavior including shape memory effect of complex SMA structures that have never been analytically studied, and provide quantitative analysis for many diverse applications of shape memory alloys. A general design method for shape memory alloy actuators has also been developed based on the developed constitutive relation and transient thermal considerations. The design methodology provides a quantitative approach to determine the design parameters of shape memory alloy force actuators, including both bias spring SMA force actuators and differential SMA force actuators.