The current trend towards the adoption of retreat longwall mining methods and the associated rapid development of the access drivages has exacerbated the environmental conditions experienced within these workings. The combined use of roof bolt and continuous miner systems has improved the face advance rate within rapid development drivages. In order to maintain adequate dust and gas control it is essential that the auxiliary ventilation and monitoring systems are correctly installed and maintained. The causes of many potential environmental hazards experienced within auxiliary ventilated rapid development drivages, are often attributed to a failure by the workforce and supervisory officials to maintain the correct installation, maintenance and operational standards of the ventilation and mining systems. The potential ventilation hazards encountered may include: the failure to deliver the required fresh air quantity and velocity to rapidly dilute and disperse methane gas liberated in the vicinity of the cutting face, or the failure to maintain sufficient exhaust air quantity in the vicinity of the cut to adequately capture dust produced on cutting and loading of the extracted mineral. Results of recent research studies have demonstrated that validated Computational Fluid Dynamics (CFD) simulation models can adequately replicate examples of good and bad ventilation. CFD models may be constructed and solved to examine the relative ventilation benefits produced by alternative mining and auxiliary ventilation configurations. These models enable the practitioner to predict and visualise the velocity, pressure and contaminant fields within an auxiliary ventilated drivage. This research project has developed a prototype educational aid, which animates and visualises these airflow and pollutant dispersion patterns within a Virtual Reality (VR) model. By introducing a pollutant such as methane into the CFD models, the VR simulation highlights regions of potential methane concentration build-up to the trainee. The application also allows the user to select/investigate the environmental consequences of enacting a number of remedial actions.

Palaeocene high-latitude coals from the Todalen Mbr. Central Tertiary Basin, Svalbard present an opportunity to understand the processes which controlled Arctic peat formation. Coals from this region have produced sub-economic quantities of bitumen during the 1920’s. Previous palaeogeographic models show significant variation between studies favouring deltaic and tidal wetland conditions. In addition, coal geochemistry studies have been limited to characterisation with little integration with palaeogeographic studies. This study utilises a large database of drill-logs to create cross sections and coal isopach maps to examine the spatial relation between seam thickness and palaeotopography. Palaeotopography is defined by mapping a ‘valley indicator’; the Grønfjorden bed, a fluvial conglomerate representing the first Palaeocene sedimentation. In addition, organic petrology organic and inorganic geochemistry were applied to samples from two mine sections and two boreholes to examine how coal quality and oil potential changed both within and between seams. The cross sections and isopach maps reveal that landscape had a significant but diminishing control upon peat accumulation. Thickest peats consistently formed at the break-in slope whilst topographic lows acted as areas of preferential channel formation and conduits for clastic sedimentation. Evolution of the landscape control had a significant control upon groundwater supply. As landscape control decreased the coals moved from isolated, raised bogs (Svea Seam) to laterally expansive minerotrophic fens (Svarteper and Askeladden Seams). Evidence of increasing marine influence and higher groundwater input was also observed from the Svea Seams to the Askeladden seam. In the Svea Nord and Longyear seam, supply of lithophile elements (Al, Ti, Na, K) is shown to be controlled by dust supply controlled by orbital cyclicity. By the Svarteper/Askeladden period lithophile element concentrations are controlled by clastic supply. Ca, Mg and Fe appear to be derived from groundwater. Sulfur concentration primarily reflects the supply of marine sulfur. Upper Todalen coals (Longyear, Svarteper and Askeladden) have significantly more oil potential than the Svea Seams with estimated retorting yields of 170-190kg/ton vs. 50kg/ton respectively. The Longyear seam exhibits relatively high HI values (ca. 300-400 mg/g TOC) consistent with a mixed Type II/III kerogen source. Greatest oil potential is shown to be favoured by formation within a fen environment, with high bacterial degradation (>100μg/g TOC hopanes), marine influence (>0.5wt% sulfur, Fe/S <0.9) and the unique temperate high lattitude Palaeocene climate of Svalbard, leading to preservation of hydrogen rich organic matter via organo-sulfur bond formation.

<p>The flow of thickened mine tailings within a tailings storage facility is a complex interaction between unconstrained viscoplastic free surface flow and possible coarse particle settling within the flow depth. The broad focus of this work is developing a robust framework for modelling tailings beach flows. Modelling tailings flow evolution in three dimensions within a storage facility will ultimately provide greater understanding of beach slope formation, as well as the ability to optimize deposition sequencing. This thesis focuses on the first step of developing a tailings model considering the transport and settling of mono-sized coarse particles within two dimensional (length and depth) laminar viscoplastic carrier fluid sheet flow. The 2D model consists of a semi-implicit finite difference shallow water sheet flow model for predicting the viscoplastic flow depth and discharge down the beach. The coarse particle transport and hindered settling within the flow are predicted using a scalar transport model. The scalar transport and shallow water flow model are coupled together using coarse particle rheology augmentation. Two key novel advancements were made through the model development. The first is coupling the coarse particle rheology augmentation within the free surface flow to the coarse particle hindered settling behavior with depth. This coupling allows for the rheology augmentation due to the coarse solid fraction to be incorporated seamlessly into both the fluid flow solver and the particle settling model. The second advancement is expanding the rheology augmentation and hindered settling coupling to particle flows beyond the Stoke?s flow regime. Ultimately, the 2D model results are compared against Spelay?s (2007) laminar settling experimental measurements for oil sand thickened tailings (TT) and composite tailings (CT) slurries, along with Spelay?s 1D settling model. The 2D model provides improved prediction of the particle concentration profiles within the fluid flow compared to the 1D model. The 2D model is also able to predict the increase in flow depth due to the particle accumulation on the bed, as well as the downslope particle transport and settling behavior.

To understand the formation of bimodal ferrite grain structures (i.e. mixed coarse + fine grain sizes) in TMCR HSLA steel plates, as-continuously cast HSLA steel slabs with varying microalloying additions (Ti, Nb and V) were reheated to temperatures in the range 1000-1300 °C and deformed at 1110 °C and 980 °C temperatures in Gleeble 3500. The interdendritic segregation during continuous casting and the consequent inhomogeneous microalloying precipitate distributions (with interdendritic regions being the precipitate-rich regions) has resulted in severely bimodal austenite grain structures under certain reheat conditions (due to the significantly higher pinning force in solute-rich regions compared to solute-poor regions). The segregation of microalloying elements can also promote bimodality during deformation by affecting the local recrystallisation kinetics. Notch-bend fracture tests were performed at –160 °C to investigate the effect of a bimodal grain size distribution on fracture toughness by comparing local fracture stress values for uniformly fine, uniformly coarse and bimodal ferrite grain structures. Analysis of local fracture stress values suggests that bimodality can raise the scatter in the fracture test results and therefore, it is undesirable. Current methods of measuring bimodality are not useful at consistently quantifying small differences in bimodality between microstructures of steel, and hence, two easy-to-measure parameters (peak height ratio, PHR and peak grain size range, PGSR) have been suggested in this study to quantify bimodality in HSLA steels.

In the current study, copper nanowires are fabricated by filling the nanochannels of anodic aluminium oxide (AAO) templates using electrodeposition. The nanowires with different growth orientations as well as twin boundaries in some cases are obtained. Cu micropillars are machined from bulk materials using focused ion beam (FIB) milling. The micropillars oriented in the [235] and [156] directions, with and without a twin boundary, with a cylindrical or square shape and with different sizes are prepared. These pillars are then compressed by a nanoindenter equipped with a flat tip, and the stress-strain curves are obtained. The morphologies of the pillars are observed using scanning electron microscopy (SEM). Thin foils of the pillars are prepared by FIB and examined using transmission electron microscopy (TEM) and scanning TEM (STEM). Finally, the dislocation structures are analysed to shed light on the investigation of the deformation mechanisms.

Since mechanical properties of cast Al-Si-Mg alloys are directly influenced by microstructural defects, understanding the characteristics of these defects and any interactions between them is important for improving the properties of castings. This research studied the effect of the most common defects normally found in cast aluminium alloys namely, double oxide films, Fe-rich phase, and porosity. A different level of each defect was introduced into the castings to investigate their effects on tensile properties with the results analysed by Yate’s algorithm and Weibull statistical analysis to determine their relative effects. The most important defect in this research was the oxide film that had an effect on UTS and elongation of about 21 MPa and 0.9% respectively and on the UTS Weibull modulus and elongation Weibull modulus of about 37 and 3 respectively. Increasing Fe content from 0.1 to 0.5 wt% influenced the tensile properties of the castings by decreasing the UTS and elongation by about 28 MPa and 1.7 % respectively. Although Fe-rich phases produced the greatest effect on tensile properties, their relatively high Weibull modulus showed that the reliability of the castings was at least predictable compared to the effects associated with oxide films. The porosity defects caused by an increase in hydrogen content from 0.1 to 0.45 ml/100g metal were the least detrimental to tensile properties. The most important interaction found in this research was the interaction between oxide films and porosity suggesting a mechanism for porosity formation in which entrained oxide film acted as initiation sites for pore formation in the castings. The main factor in the formation of porosity was hydrogen and shrinkage, since both could encourage the expansion of the oxide film defects to become gas porosity or shrinkage porosity in the castings. The other interaction between the microstructural defects observed in this research was that oxide films were found to be substrates for the nucleation and growth of Fe-rich phases, particularly the β-Al5FeSi phase. An interaction between all three defects were also observed and it further influenced the tensile properties of the cast Al-Si-Mg alloys by decreasing UTS and elongation by about 5 MPa and 0.5% respectively and the UTS Weibull modulus and elongation Weibull modulus of about 8 and 0.6 respectively.

Five API grade steels designed for linepipe applications produced using different processing routes and with varying microstructures were studied against differences in work hardening and work softening behaviour obtained from mechanical data. The rolling history and wt % additions of alloying elements will determine how the microstructures perform under reverse deformation schedules commonly seen during large diameter linepipe fabrication as steels can undergo work softening in the reverse direction of deformation, otherwise known as the Bauschinger effect. The Bauschinger effect is known to be dependent on the initial forward pre-strain, volume fraction (VF) of carbo-nitride particles and initial dislocation density. The effects of grain size and solid solution strengthening are a matter of debate in the literature and the combined effects of all five strengthening mechanisms have rarely been quantified. TEM investigations determined the dislocation densities to be between 2.2 x1014 m-2 - 5.8 x1014 m-2 in the as received condition. Observed trends presented and discussed in this body of work have given a greater insight into the influence microstructure has on the mechanical properties across a wide range of HSLA steels of similar strength grades, which are of important consideration for future development of low carbon steels designed for the petrochemical industry.

Blends of poly(ethylene terephthalate) (PET) and polycarbonate (PC) have been prepared by twin-screw extruder with and without added a transesterification catalyst - lanthanum acetylacetonate hydrate. The blends without added catalyst are completely immiscible over the study range while the blends with added catalyst show partial miscibility. The mechanical properties are slightly improved in the latter blends. Studies were made on the crystallization and melting behaviour of PET and both of blends. It has been found that the crystallisation was inhibited in the presence of PC, particularly in the blends with added catalyst for which the equilibrium m.pt. showed considerable depression greater than the other samples. Multiple melting endotherms are due to dual lamellar thickness distributions and recrystallisation during heating. Miscibility, melting and crystallisation were also studied by MTDSC which proved to be a powerful tool separating reversing and non-reversing events. The crystallinities of PET and blends were measured using the First Law method and consistent with those measured by density and WAXD procedures. Both blends annealed at higher temperature the thermal properties, phase structure and transesterification have been investigated as a function of time. Kinetics parameters were also determined.

To improve the efficiency of turbine aero engines, higher operating temperatures and weight savings are being investigated. Alloys such as RR1000 are being trialled as they perform better at higher temperatures than current nickel-based superalloys. To achieve weight savings, inertia welding is being trialled for turbine discs but current post weld heat treatments reduce fatigue life. In this investigation, a number of novel post weld heat treatments were trialled aimed at improving post weld microstructure and fatigue properties. Extensive microstructural characterisation and mechanical testing were used to assess the effect of these treatments on both parent and weld materials. Post weld heat treatment (PWHT) was found to have a great effect on the size and distribution of γ' and carbides, particularly when a PWHT temperature of 980ºC or above was used. The effect of this microstructural change on the hardness of the weld and parent material has also been characterised. Extensive total life fatigue testing was carried out at 650ºC. It was found that failure can occur in both the parent and weld material, although it is deduced that the yield stress of the weld needs to be surpassed to see weld failure (plasticity in the weld). Increasing dwell time at peak load reduced the life of these components. Two mechanisms for crack growth were observed with initiation either at the surface or at a large Hf rich particle subsurface. Oxidation was found to have a large effect on both initiation and growth of fatigue cracks. By introducing a sharp pre-fatigue crack into samples, static load testing was used to determine a threshold value of K (stress intensity factor) for growth and growth rates were plotted at different K values. It was seen in these tests that PWHT had a large effect on growth rates and threshold values of K.

Co-Cr alloys are the most widely used metallic biomaterials for metal-on-metal joint prostheses. However, concerns about increased revision rate associated with metal-on-metal replacements have been raised recently. This research was aimed at studying the response of medical grade ASTM Fl537 Co-28Cr-6Mo alloy with different phase constituents to low-temperature plasma carburising (LTPC) to address the tribocorrosion problems of the current metal-on-metal joint prostheses. To this end, n series of heat treatments were designed to produce samples with an a-FCC dominated (>95%), an c-HCP dominated (>97%) and a dual phased (40% c-HCP) microstructures. An optimised low-temperature plasma carburising (LTPC) treatment wns applied to the heat-treated samples. The microstructure of the plasma carburised surface layers were characterised by XRD, GDS, SEMIEDX and TEM, and the properties of the surface carburised layers were evaluated using micro- a•nd nano-indentation, reciprocating wear and electrochemical corrosion tests, and tribocorrosion tests a t different electrochemical potentials. The experimental results have showed that the response of the Co-28Cr-6Mo alloy to the LTPC treatment is highly dependent on the phase constituent. The LTPC treatment can significantly increase the hardness, load bearing capacity and dry wear resistance and tribocorrosion properties of all the Co-28Cr-6Mo samples with different phase constituents.