In this thesis aluminium alloys containing small additions of both tin (~ 0.1 wt %) and gallium (~ 0.05 wt %) dissolve anodically at high rates in brine media; at room temperature, current densities > 0.2 A cm-2 can be obtained at potentials close to the open circuit potential, ~ -1.5 V vs SCE. Alloys without both tin and gallium do not dissolve at such a negative potential. The tin exists in the alloys as a second phase, typically as ~ 1 μm inclusions throughout the aluminium structure. Anodic dissolution leads to rounded pits around the tin inclusions. The pits are different in structure from the crystallographic pits observed with Al and other alloys. Clearly, the AlMgSnGa alloys dissolve by a different mechanism. Although the distribution of the gallium in the alloy could not be established, it is essential to the formation of these pits and maintaining dissolution. In addition to the composition, mechanical working and heat treatment influence both the stability of the alloys to open circuit corrosion and the overpotential for high rate dissolution, factors critical to battery performance. The correlation between performance and alloy microstructure has been investigated. Imaging with a high speed camera with a resolution of 10 – 20 μm was used to observe the dissolution of AlMgSnGa alloys. Using microelectrodes with only a few Sn inclusions in their surface, allows confirmation that hydrogen evolution occurs only from the Sn inclusions and also showed that the evolution of H2 is not continuous. Therate of H2 evolution correlates with shifts in potential between - 1.5 V and much less negative potentials. The performance of a laboratory Al-air battery with 2 M NaCl electrolyte was limited by both the performance of the O2 cathode and the extent of dissolution of the alloy. Using a cell with a low electrolyte volume/surface area ratio, dissolution of the anode stopped after the passage of 1000 C cm-2 due to a high impedance, thick film of crystals clinging to the surface. Removal of this film allowed the dissolution to recommence. The charge limitation depends on cell design but a high charge density would be difficult to achieve with a low volume battery.

This thesis aims to describe the ultra-rapid synthesis of a number of important transition metal carbides as well as investigating their reaction mechanisms. 4 binary systems are discussed; Nb-C, Mo-C, Ta-C and W-C, and work carried out on the ternary system, Nb-Ta-C, is also evaluated. Carbide production was investigated from both the oxide and elemental precursors. Ultra-rapid synthesis has been achieved through the development of a reproducible experimental technique and the investigation into a plethora of reaction variables as well as microwave applicators and powers. This resulted in, specifically within the single mode cavity, the completion of the majority of reactions within 20 s. Further development was then built upon the direct relationship observed between phase fraction results (obtained from Powder X-ray Diffraction (PXD) data), in-situ temperature and ex-situ dielectric property measurements; allowing reaction profiles of the various carbides to be mapped, as well as a crucial understanding of the effects of microwave energy on materials at various temperatures. Powder Neutron Diffraction (PND) was also used to evaluate product purity and the C occupancy of the final products, revealing non-stoichiometry which relates directly to the Tc onset observed for the superconducting transition metal carbides. This, in turn, allowed the trends observed for the ternary carbides to be explained, a linear trend does not exist between Tc and C occupancy. In an effort to develop on the understanding of solid state microwave heating, in-situ reaction monitoring techniques were investigated. Through the use of thermal imaging and high speed photography, the W-C system was observed during the crucial initial stages of the reaction process. The information obtained both corroborated previously collected data and allowed a possible reaction mechanism to be alluded to. The observation of localised heating, prior to the beginning of carbide formation, suggests possible high temperatures far exceeding those observed by optical pyrometry. This could well explain the rapid reaction times as well as suggest an interaction mechanism between carbon, an efficient microwave absorber, and tungsten, a low dielectric loss metal.

This dissertation presents the findings of a project where, following investigation and assessment, a million tonnes of sand and gravel at a contaminated former US Air Force Base was excavated for use as aggregate. The process required on-site screening for petroleum hydrocarbons of over 7,000 soil samples and provided an opportunity to assess the efficiency of the investigation, assess the application of geophysics of hydrocarbon contaminated sites, and look at the role of aggregate extraction in the contaminated land industry.

This thesis presents research into the binding, extraction and transport of the hexachloroplatinate anion, [PtCl6]2-, by organic receptors in a solvent extraction process. The target anion is produced during the processing of platinum-containing ores and the aim was to develop reagents that can selectively extract [PtCl6]2- to optimise the recovery of platinum. Chapter One outlines reasons for the interest in [PtCI6]2-and provides an overview of the processes and techniques used to refine precious metals. An introduction to anion coordination chemistry relevant to the research project is also presented. Chapter Two discusses the design features incorporated into organic receptors to enable strong and selective binding of [PtCl6]2-. These features include a tertiary amine protonation site, hydrogen-bond donor groups and organic solubilising moieties. The synthesis of a series of functionalised tripodal tris(2-aminoethyl)amine based receptors with sulfonamide, amide, urea, thiourea or pyrrole NH hydrogenbond donor groups are reported. Complexation reactions between the receptors and H2PtCl6 to form [(LH)2PtCl6] ion pairs are discussed. Crystallographic analysis of the [(LH)2PtCl6]complexes with TREN-based sulfonamide, urea and amide receptors confirms the presence of hydrogen-bonds between the NH donor groups and the outer-sphere of [PtCl6]2-. The low organic solubility of the complexes prevented the study of these systems in solvent extractions. Chapter Three describes the variation of terminal substituents of the tripodal receptors with the aim of improving the organic solubility of the extractants and their [PtCl6]2-complexes. In these "second generation" receptors the terminal substituents assessed include 3, 5-dimethylphenyl, 4-iso-propylphenyl, 4-tert-butylphenyl, 3, 5- dimethoxyphenyl, 3, 4 dimethoxypheynl and 3, 4, 5-trimethoxyphenyl. Through reaction of the receptors with H2PtCl6 the solubility of the resultant complexes are assessed. Chapter Four describes the development of an optimised solvent extraction method to study the extractive behaviour receptors. A pH swing mechanism is utilised to control the uptake and release of [PtCl6]2-. The extraction results for trioctylamine and the soluble tripodal urea and amide receptors are compared. Attempts are also made to confirm the stoichiometry of the complex in solution. Chapter Five describes the synthesis of tris(2-aminoethyl)amine based receptors with hydrogen- and halogen-bond donor groups with the aim of increasing the strength of the interaction between a receptor and [PtCI6]2-. Receptors with an extended tripodal scaffold based on a tris(3-aminopropyl)amine with urea and amide moieties are also presented. The results of the complexation reactions and solvent extraction studies with these modified extractants are presented. Chapter Six presents the design and synthesis of bipodal and monopodal receptors in order to assess the role of the number of hydrogen-bond donor functionalised arms. The results of the solvent extraction studies with these receptors are discussed and comparisons made between tripodal, bipodal and monopodal extractants. The crystallographic analysis of the [(LH)2PtCl6] complexes formed between the bipodal urea and amide receptors is described. Chapter Seven highlights the important findings from this work. Conclusions are drawn as to the optimum receptor system developed and this is compared to the extractant system thought to be in current use for the extraction and transport of [PtCl6]2-.

Low temperature plasma surface alloying with nitrogen (nitriding), carbon (carburising) and both (carbonitriding) has been successfully employed in hardening medical grade ASTM F138, ASTM F1586 and ASTM F2581 as well as engineering grade AISI 316 by the formation of a modified layer better known as S-phase or expanded austenite. In this study, systematic plasma treatments and characterisation were performed on medical grade stainless steel in order to establish the optimised treatment conditions, especially temperature, which can maximise the hardened case depth without any detriment in corrosion resistance. The surface of a biomaterial must not adversely affect its biological environment and return the material surface must not be adversely affected by the surrounding host tissue and fluids. Experimental results have shown that this duality of concern can be addressed by creating S-phase. It has been shown that low-temperature nitriding (430°C), carburising (500°C) and carbonitriding (430°C) improved the localised corrosion, corrosion-wear and fretting-wear resistance of these medical grade stainless. Also biocompatibility studies have proved that these hardened surfaces were biocompatible under the realms of the tests conducted in this study therefore the use of hardened medical grade austenitic stainless steel might be suitable in implant applications.

This thesis reports on an environmentally-friendly pultrusion technique for the production of fibre-reinforced composites, termed as “clean pultrusion”. In this new manufacturing technique, the resin bath used in the conventional pultrusion was replaced with a custom-built resin impregnator. The resin impregnator was designed and built to impregnate the rovings using a combination of pin, injection and capillary-based impregnation. An integral aspect of the clean pultrusion process was spreading of the filaments in the rovings, via mechanical means, prior to impregnation. An automated fibre spreading rig was designed and built based on “tension-release” process. The rig-design was optimised using Taguchi method. The physical, mechanical and thermo-mechanical properties of the composites pultruded using the clean and conventional techniques were compared. It was found that the composites manufactured using the clean pultrusion exhibited lower void and better mechanical properties. A life cycle assessment (LCA) was also performed to compare the environmental impact of the clean and conventional pultrusion processes. The LCA demonstrated conclusively that the clean pultrusion technique offers several environmental advantages over the conventional resin-bath pultrusion. The new pultrusion technique was demonstrated as being a viable method to pultrude composites without using a resin bath.

Microstructural analysis and mechanical property assessment have been carried out on hot isostatically pressed (HIPped) and heat treated samples of RR 1000 powder to assess Net Shape HIPping as a process-route for aero engine components. HIPping led to (Hf,Zr)-rich oxides and carbides on prior particle boundaries (PPBs) which could be coarsened, but not eliminated by changing the HIP procedure. HIPping above the γ′ solvus resulted in coarser grains with serrated boundaries and in the formation of irregular-shaped secondary γ′ and fan-type γ-γ′ structures. Factors which influence the growth and morphology of γ′ particles are considered and it is shown that particle impingement dominates in the formation of irregular γ′ during continuous cooling from supersolvus. Solution treatment near the HIPping temperature led to thermally induced pores (TIP) but lower temperatures avoided TIP and changed the γ′ size, distribution and morphology giving a large volume fraction of finer cuboidal secondary γ′ and medium-sized spherical tertiary γ′.

Between 50% and 70% of the total energy used in the extraction process may be attributed to comminution. Microwave pre-treatment has been suggested as a means to decrease the energy requirements. A variety of mineral ores have been investigated and the effects of microwave radiation quantified in terms of the mineralogy, changes in the Bond Work Index, flotability and magnetic separation. It has been shown that microwave pre-treatment is most effective for coarse grained ores with consistent mineralogy consisting of good microwave absorbers in a transparent gangue (up to a 90% decrease in Bond work index for Palabora copper ore) whereas fine grained ores consisting predominantly of good absorbers are not affected as well (a reduction of only 25% in work index for Mambula ore). Although the mineralogy of minerals are affected by exposure to microwave radiation, flotability and magnetic separation characteristics have been shown not to be adversely affected, unless the microstructure is completely destroyed after prolonged microwave exposure. Computer simulations have shown that significant changes to comminution circuits are possible as a result of microwave induced work index reductions (three mills reduced to one). Purpose-built microwave units may hold the solution for more efficient mineral extraction in the near future.

Linear friction welding (LFW) of two α - β titanium alloys, Ti-6Al-4V (Ti64) and Ti-6Al-2Sn-4Zr-6Mo (Ti6246) was studied, focusing on micro-hardness measurement, microstructure and texture characterisation. It has been found that in the as-welded condition Ti6246 has lower micro-hardness values in the weld region than in the base material, while for Ti64 the weld region is harder. The change in hardness is greatly related to the microstructures formed after welding. In cnetre weld zone (CWZ), in the autogenous Ti6246 weld, the microstructure consists of fine β grains with needle shape orthorhombic α″. In the autogenous Ti64 weld, relatively large acicular martensitic α′ phase was found. A very strong texture component, where the basal pole is concentrated in the sample normal direction and one of the {11 20}α poles is concentrated in the oscillation direction, is identified in both the CWZ and thermo-mechanically affected zone. Comparison between the α texture and the β texture suggests that the strong texture component T is the consequence of the deformation β texture developed at high temperature and the preferred variant selection during the β→α transformation. The texture was found to have significant influence on the fracture toughness of the weld region.

Lithium is considered a borderline strategically important metal for the UK due to the limited availability of primary deposits, of sufficient grade, for economic processing (Naden, 2012). The rising demand, of approximately 10% yearly, has promulgated investigations for the development of secondary sources of lithium in order to secure long term reserves for the UK and Europe (Jaskula, 2015). The British Geological Survey (1987) estimated that the St Austell granite contained up to 3.3 million tonnes of recoverable lithium. Imerys Ltd also identified lithium-bearing mineral in their kaolin waste material in Beauvoir, containing up to 0.89 wt.% Li2O. The lithium-bearing minerals identified were; lepidolite (K(Li,Al)3(Si,Al)4O10(F,OH)2) and zinnwaldite (KLiFeAl(AlSi3)O10(F,OH)2), which can contain between 3.0 to 7.7 wt.% Li2O and 2.0 to 5.0 wt.% Li2O, respectively (Garrett, 2004). Lithium flotation concentrates containing up to 5.0 wt.% Li2O were optimised for the Beauvoir waste material with up to 80% lithium recoveries, whereas a lower flotation grade of 0.5 wt.% Li2O was found for the St Austell material. The St Austell waste materials did not prove viable to process via conventional flotation routes hence a novel process route for the bio-recovery of lithium from lithium rich micas was developed. Extraction of lithium by bioleaching has demonstrated the ability of fungi, of Aspergillus niger group, to leach lithium from the lepidolite in significant quantity, achieving 125mg/L of lithium in solution after twelve weeks of bio-leaching, at a recovery of 45%. Following this research, Imerys are applying to build a pilot plant, securing funding through the Innovative UK grant.