As a result of the increasing energy demand but a heavy dependence on easy-to-produce conventional oil, vast reserves of recoverable heavy oil have been left untapped. According to the International Energy Agency, IEA, fossil fuels – oil, coal, natural gas – will still predominate, despite a decline in their overall share, towards meeting the increasing world energy demand. While heavy oil has been predicted to account for an increasing share, contributions from conventional light oil have been predicted to drop from 80% to 53% in the next two decades (IEA, 2013b). Therefore, the large reserves of the under-utilised heavy oil, if extracted cost-effectively and in an environmentally friendly manner, will facilitate the meeting of both the short and long term energy demands. In this work, different thermal heavy oil recovery processes were reviewed with particular attention given to the air injection processes. In-situ combustion, ISC, has been identified as the most efficient and environmentally friendly technique used to recover heavy oil. Until the last decade, there was only a small interest in the conventional ISC. This is due to the complex nature of the processes taking place during ISC and the lack of success recorded over the years. The successful pilot scale testing of the Toe-to-Heel Air Injection, THAI, by Petrobank has revived interest both industrially and in the academic environment. Experimentally, THAI has been consistently proven to exhibit robust and stable combustion front propagation. Among the advantages of THAI is the ability to incorporate the in-situ catalytic upgrading process, THAI-CAPRI, such that further catalytic upgrading is achieved inside the reservoir. To realise the theoretical promise offered by THAI-CAPRI, there is a need to develop a reliable numerical simulation model that can be used to scale laboratory experiments to full field scale. Even for 3D combustion cell experiments, only one such model exists and it is incapable of predicting the most critical parameters affecting the THAI process. Therefore, the subject of this work was the development and identification of an accurate and reliable laboratory scale model that can then be used to develop field scale studies and investigate the effect of reservoir geology on the THAI process. However, because of the significant uncertainty introduced by the kind of kinetics scheme used and the fact that the main mechanism through which fuel deposition takes place is still a contentious issue, three different kinetics schemes, based on Athabasca bitumen, have been tested for the model of the 3D combustion cell experiment. All the models offered an insight into the mechanism through which oxygen production begins. They revealed that oxygen production was as a result of the combustion front propagating along the horizontal producer (HP). They also showed that the presence of coke inside the horizontal producer is an essential requirement for stable combustion front propagation. It was also observed that LTO is not the main mechanism through which fuel is deposited as oxygen does not bypass the combustion front. The models also showed that the temperature around the mobile oil zone (MOZ), where catalytic reaction in the CAPRITM is envisaged to be located, will not be sufficient to make the hydro-treating catalysts effective. Therefore, it is concluded that some form of external heating must be used in order to raise the temperature of the catalyst bed. Two out of the three different Arrhenius kinetics schemes that were successfully used to history-match the 3D combustion cell experiment were adjusted and implemented in field scale simulations. This is because the kinetics parameters obtained from the laboratory scale model cannot be used directly for the field scale simulation as they led to excessive coke deposition. A comparative study, between the two kinetics schemes, showed that the adjusted direct conversion kinetics predicts higher oil rate, and higher air rate can be injected right from the initiation of the combustion compared to in the case of the split conversion kinetics. The direct conversion kinetics was then used to study the field performance because it provided a more realistic representation of the physicochemical processes than the split conversion kinetics. The study revealed that even if the combustion front swept the whole reservoir length, it has to propagate along the horizontal producer for oxygen production to take place. It was observed that the combustion zone does not only have to cover the whole reservoir length but also has to expand laterally in order to produce the whole reservoir. For heterogeneous reservoirs, the THAI process was found to have larger air-oil ratio (AOR) in reservoir containing a discontinuous distribution of shale lenses compared to the homogeneous model. However, overall, the THAI process is only marginally affected in terms of cumulative oil recovery. The combustion front was found to propagate in a stable manner just like in the homogeneous model. However, further study is needed to investigate the effect of different permeability distributions would have on the THAI process. This should allow the optimum location of the wells to be determined. Studies of the effect of bottom water (BW) on the THAI process have shown that the oil recovery is heavily affected depending on the thickness of BW zone. It was found that the location of the HP well relative to the oil-water interface significantly affects the oil production rate and hence the cumulative oil produced. More oil is recovered when the HP well is located inside the BW zone. It was found that a ‘basal gas layer’, just below the oil-water interface, is formed when the HP well is located in the BW zone. The study has shown that there is a limit to BW thickness above which the THAI process cannot be applied to a BW reservoir. However, future work is needed to determine this BW thickness. The reservoir cap rock, depending on it is permeability and porosity, only marginally affects the oil recovery in the THAI process. It was found that the cap rock aids in heat distribution to the extent that most of the upper oil layer is mobilised. However, the effect is observed to be less pronounced with increased permeability and porosity. Future work should look into whether longer operation period has an adverse effect on the stability of the combustion front, and thus on the overall performance of the THAI process.

Additive manufacturing of aluminium alloys using selective laser melting (SLM) is of research interest nowadays because of its potential benefits in industry sectors such as aerospace and automotive. However, in order to demonstrate the credibility of aluminium SLM for industrial needs, a comprehensive understanding of the interrelation between the process parameters, produced microstructure, and mechanical behaviour is still needed. This thesis aims at contributing to developing this comprehensive understanding through studying the various aspects of the process, with investigation of the powder raw material to the near fully dense samples, focussing on the alloy AlSi10Mg. The primary building blocks in the SLM process are the single tracks. Their formation is affected by the physical properties of the material that control the laser-material interactions. Keyhole mode melting was found to be dominant when processing AlSi10Mg, producing conical-shaped melt pools. Porosity was not evident in single tracks and individual layers. Satellites and balling defects, however, were observed on top of the tracks and layers at higher scan speeds, which contribute to porosity formation with layer progression. The combination of process parameters controls the amount of porosity formed, with the scan speed controlling the type of pore; metallurgical or keyhole pore. A pre-melt scan strategy significantly reduced porosity and successfully produced 99.8% dense samples. Furthermore, the pre-melt scan strategy was seen to effectively reduce the number of pores developed when using powder that does not fully comply with the process standards. The gas flow rate within the process chamber controlled laser spatter and condensate removal during processing, which in its turn affected the degree of porosity in the samples. The SLM process resulted in an AlSi10Mg alloy with a characteristically fine microstructure, with fine equiaxed grains at the melt pool core and coarser elongated grains at the boundary. The material showed a strong texture, owing to directional solidification. Cellular dendritic Al with inter-dendritic Si was observed. The material was subjected to a T6 heat treatment that transformed the microstructure into spheroids of Si in the Al matrix. This study investigated, for the first time, the local mechanical properties within the SLM material using nanoindentation. This showed a uniform nano-hardness profile that was attributed to the fine microstructure and good dispersion of the alloying elements. Spatial variation within the material was recorded after the T6 heat treatment due to phase transformation. This study is also the first to report on the compressive behaviour of solid SLM material, which is important for developing prediction and simulation models. The heat treatment softened the material and provided it with an increased ductility under indentation, tensile, and compressive types of loading. In addition, the material showed good fatigue performance, which was further improved by heat treatment and machining to obtain a smoother surface roughness. This investigation has, therefore, developed an understanding of the various aspects of the SLM process yielding near fully dense parts and defined the microstructure-mechanical property interrelation promoting the process for Al alloys in a number of industrial sectors.

Fluidised bed combustion (FBC) has been identified as one of the best technologies available for lump coal combustion. A major drawback during prolonged operation of FBC systems particularly bubbling fluidised bed (BFB) systems is sintering and agglomerate formation of bed material that affects performance efficiency and reliability in industrial applications as exemplified at Associated British Sugar (AB Sugar). The mechanisms responsible for sintering and agglomerate formation in this type of system need to be understood, to promote continual use of this technology for efficient coal utilisation. The first set of investigations focused on agglomeration properties of bed material (Garside 14/25 sand) used in Industrial FBC at AB Sugar. Bed material was calcinated between 800 and 1200°C in a high temperature furnace in the absence and presence of coal (three types of bituminous coals) or coal ash. Results showed sintering and agglomerate formation of bed material can occur in the absence of coal or coal ash at a calcination temperature near 1200°C. Addition of coal or coal ash further promotes sintering and agglomerate formation at 1000°C. Combustion stages appears to influence surface morphology, chemistry and mechanisms of agglomerated bed material based on similarities observed in the agglomerated bed material formed from calcination of Garside 14/25 sand bed material mixed with coal, and those formed in industrial scale FBC during combustion of lump coal. The second set of investigations used two different lump bituminous coals classified as washed (undergone washing process to remove mud/shale stone) or unwashed (still containing the mud/shale) from the same mine (Blyth, typically referred to as Blyth coals) as those used in the AB Sugar industrial FBC. Combustion of washed and unwashed Blyth lump coals (9 to 19 mm particle size) was investigated in a 30 kW pilot scale bubbling fluidised bed combustor (PSBFBC) during normal combustion and crash stop combustion runs. This simulated conditions in the AB Sugar Industrial FBC system with a thermal rating of approximately 30 MW, which uses larger coal particle size of 12 to 25 mm. Results reveal unwashed Blyth lump coal in the PSBFBC and industrial FBC causes some sintering and agglomerate formation of the bed material over short operation periods of 52 and 240 hours respectively, which was not observed in the washed Blyth coal system over a similar operating period. Observed sintering and agglomeration formation in unwashed Blyth coal is mainly attributed to accumulation of mud/shale stones in the bed, which would have been mostly removed by the washing process. The crash stop combustion run, done to simulate the fan trip scenario in the industrial FBC system, promoted sintering and agglomerate formation in the PSBFBC, possibly due to the 30 to 50°C temperature rise in the bed when fluidised air was stopped. Continuous deposition and increasing concentration of mud/shale stones in the bed affects the localised temperature as well as the fluidising properties and quality, eventually promoting sintering and agglomerate formation. PSBFBC bed height, bed material particle size and measured pressure drop also increase with increasing operating time and mud/shale stones deposition in the bed. Deposition of coal ash to the surface of the bed material (sand) in the PSBFBC was analysed by the use of SEM-EDX and XRF. The deposition of ash to the surface of PSBFBC bed material sand increases as the operation times increases, as identified by increasing concentration of Al, K and Ca on fluidised bed sand particle surfaces in their stable oxide forms of Al2O3, K2O and CaO respectively.

Die wear is always an important issue in hot forming processes, such as in forging and extrusion. Die life affects the economics of process to product and in order to optimise die life, the mechanism of wear should be approached scientifically. The aim of this work is to provide a systematic method for predicting and quantifying wear occurring in the extrusion of INCONEL 718 (IN718), nickel superalloy. To characterise wear, the process prediction which contributes to it must be identified and quantified. First, material characterisation was carried out using the Gleeble physical materials simulator. Then a set of unified viscoplastic constitutive equations was developed suitable for modelling microstructural evolution of IN718, i.e. evolution of average grain size, dislocation density and recrystallisation under hot forming conditions, which enabled resulting flow stress to be calculated and the microstructure of formed parts to be predicted. Second, heat transfer and friction during the forming process were investigated, by upsetting cylinders and performing ring tests on IN718. The heat transfer experimental work centres rounded the development of a reliable method for the measurement of the sub-surface temperatures in the bottom die during upsetting. The experimental values of sub-surface temperatures under various lubrication and forging conditions were analysed. A theoretical approach was proposed for the determination of the values of effective heat transfer coefficient and effective friction factor, and comparisons of experimental results and those from FE simulations were made and satisfactory matchings were obtained. Finally, integration of the material model and derived boundary conditions using subroutines for FEA are presented. Qualitative studies of abrasive die wear carrying out in a FE package, DEFORM, on the effect of various hot forming cases are shown. The numerical results are compared with the observations from mechanical measurements and metallurgical examinations for the studied die. Good correlations are found for most cases, which prove the presented methods can be used effectively in the prediction of die wear. Also, further work is suggested to enhance the modelling capabilities.

Small-angle scattering technique uses the scattering of radiation (e.g. neutrons or X-rays) at small angles to probe large-scale structures withjn matter, up to thousands of Angstroms. It is proven a valuable tool for investigating precipitation in reactor pressure vessel (RPV) steels and Fe-Ga alloys offering a statistical average over a large volume of samples. RPV steels, being of crucial importance for the longevity of a nuclear reactor, have been a long-standing theme for investigations. The main topics of such investigations are the effects of irradiation upon the steels and the consequent implications on their macroscopic properties. In this thesis, small-angle neutron scattering is employed to investigate irradiation induced precipitates in low- and high-Cu RPV steels. After irradiations with protons to low damage levels, precipitates could be clearly observed only in the high-Cu RPV steels. Stable preirradiation formed features are attributed to precipitation of carbides. Fe-Ga binary alloys have attracted much attention due to the still unexplained high magnetostriction they exhibit. To investigate the composition of nanoheterogeneities in a Fe-Ga sample, anomalous small-angle X-ray scattering is employed exploiting the energy dependence of the Fe and Ga atoms near their respective absorption edges. The nanoprecipitates are found to have a Fe3Ga stoichiometry.

We study the low temperature magnetic ordering of rare-earth pyrochlores. The dominant magnetic interaction: nearest neighbour antiferromagnetic Heisenberg exchange, is frustrated with a macroscopic ground-state degeneracy. This degeneracy is lifted by weaker interactions, stabilising long-range order. First we study the dipolar governed gadolinium stannate with an external magnetic field. Factorising the Hamiltonian in terms of ten quadratics provides exact solutions to the over-constrained model with fields orientated along highly symmetrical directions. Next we study the isostructural gadolinium titanate: the much more complex magnetism is indexed by a different propagation-vector to gadolinium stannate due to further neighbour exchange interactions. This material is controversial: elastic neutron scattering and Mössbauer experiments have been using contradictory interpretations. We propose a new state which appears to resolve this inconsistency. Finally we model erbium titanate, which is approached differently due to the dominant crystal-field. Existing elastic neutron scattering data is reexamined and found inconsistent with the state currently discussed in the literature so we suggest an unusual multiple-q state. The spins are not orientated along the expected crystal-field direction: a consequence of frustration. Energetics are studied phenomenologically. We suggest that experimentally observed gapless spin-waves control transfer of spin density between different q-points of the proposed state.

This thesis presents the work done to characterise two superconducting materials. We study BiPd, a non-centrosymmetric superconductor which is theoretically expected to show signs of spin singlet and triplet mixing due to the strong spin-orbit scattering of its composing elements. We map the field-temperature superconducting phase diagram along two crystal directions using Small Angle Neutron Scattering (SANS), magnetisation and \(µ\)SR measurements and determine the microscopic parameters defining the superconducting state. We also uncover a rare behaviour displayed in low-\(k\) superconductors, the Intermediate Mixed State, which causes domains of vortex lattice with constant spacing to coexist with Meissner domains at low applied fields. Finally we show evidence that, unlike what was expected, the superconductivity in BiPd behaves conventionally. The second material studied is Nb3Sn, widely used to produce large magnetic fields in various devices such as MRI machines. We investigate the superconducting state of several polycrystalline samples with different tin concentrations, as recent evidence point towards a lack of change of the upper critical field with varying Sn doping, in contradiction with older measurements that see a drop in H\({c2}\) associated with the apparition of a structural (martensitic) crystalline transition. Using SANS, we show that these recent results were likely not measuring the bulk state of Nb3Sn and that we find large variation of H\({c2}\) with Sn concentration. We also present indications that the vortex lattice is influenced by non-local effects at large fields by measuring the change in the vortex lattice structure with field. Lastly, our measurements are consistent with a full single gap behaviour in Nb3Sn.

The grain growth behaviour during reheating between 950 ºC and 1300 ºC of as-cast Al-Nb steel (containing 0.019 wt% Nb and 0.057 wt% Al) and rolled Nb-containing steel (containing 0.028 wt% Nb and 0.031 wt% Al) have been investigated. In particular the role of microalloying element segregation during casting and, hence the spatial distribution of microalloying precipitates, on grain boundary pinning during reheating has been considered. The Al-Nb containing steel has been examined in separate initial conditions, including as-cast (segregated structure), homogenised and forged (reduced separation of segregated bands) samples. It was found that microalloy segregation occurred between the dendritic and interdendritic regions, where the secondary dendrite arm spacing (SDAS) was 150 ± 50 μm. Nb showed strong segregation into the interdendritic regions resulting in a higher number density of Nb(C,N) precipitates (2.64 × 104 /mm2) compared to the dendritic region (0.73 × 104 /mm2). However, Al did not show strong segregation resulting in relatively well-distributed AlN precipitates in the matrix (1.29× 104 /mm2 in the interdendritic region and 1.89× 104 /mm2 in the dendritic region). After forging, the separation between the segregated bands was reduced to 65 ± 10 μm from the previous 150 ± 50 μm in the as-cast sample. The increased Nb content in the rolled Nb-containing steel compared to the Al-Nb steel gave a greater extent of segregation in the solute-enriched regions resulting in a larger number density of Nb(C,N) present (5.9× 104 /mm2), whilst the separation between in the segregated bands in the as-rolled Nb-containing steel was 35 ± 10 μm.

Electronic structure calculation methods, coupled with unbiased global optimization schemes are developed and employed, for the exploration of the energy landscape of subnanometre scale metallic clusters of noble metals. Structure prediction, along with statistical analysis of the potential energy surfaces for ultrasmall metallic and bimetallic particles of the coinage metals (Cu, Ag, Au) and platinum group metals (Pd, Pt) is undertaken, to determine favourable cluster geometries. Prediction of energetic and electronic properties, including charge distributions, electronic and configurational densities of states, binding, adsorption and mixing energies are made, in order to support the predictions of novel experimental work on a potential catalytic and optoelectronic systems. The environment of the particle is a focus, with surface-bound, ligated and gas phase clusters all considered, in addition to modelling of the adsorption of small molecules. Subnanoscale metal systems show promise in a range of reactive and electronic roles, and by producing accurate theoretical predictions of optical, binding and electronic properties, we contribute to the rational design of such new materials.

Shot peened steel tubing made from 304HCu-grade austenitic stainless steel was exposed to temperatures of 600-750°C in three atmospheres: vacuum, deoxygenated atmospheric pressure steam and deoxygenated 70bar steam. The microstructural changes and oxide morphologies of the shot peened material were observed with SEM, TEM, microhardness testing and TKD mapping. An estimate of the lifetime of the shot peened microstructure in service conditions was made based on service temperature. MnCr2O4 spinel was observed on oxidized samples and the consequences of this are discussed.