The work in this thesis aims to investigate the ductility of s-HD (solid hydrogenation disproportionation) processed book mould cast NdFeB material in order to develop a novel processing route for producing fully dense magnetic material with a high energy product. A major drawback of NdFeB–based alloys is that they are extremely brittle. Therefore, to produce a fully dense magnet these alloys must be broken down into a powder and hot pressed or sintered followed by cutting and grinding to the desired shape and precise dimensions. This process is time consuming, energy intensive and produces a significant amount of waste which is not readily recyclable. This thesis reports a potentially new application of hydrogen as a promising high temperature processing tool in which the normally brittle Nd\(_2\)Fe\(_1\)\(_4\)B based intermetallic absorbs and reacts with hydrogen, converting it into a ductile, disproportionated condition, which can be subsequently compressed at room temperature. It can then be restored to its original state by removal of the hydrogen under partial vacuum at elevated temperatures. By maintaining a solid form throughout, almost zero waste material is produced and the deformed material exhibits a high coercivity and a useful degree of anisotropy.

Surface damage can be introduced into rotor disc components during assembly, maintenance and overhaul operations for aircraft engines. This is known as handling damage and is often in the form of surface scratches, which are known to reduce total component fatigue life. This work provides a holistic understanding of the effect of artificial scratch damage on the fatigue performance of a nickel-based superalloy used for compressor and turbine disc applications. Following extensive analysis of results from previous test programmes completed at Rolls Royce plc., a series of low cycle fatigue tests were performed on Alloy 720Li specimens. A test matrix was designed to isolate and identify every factor that may contribute to the fatigue properties of scratch damaged components. The geometry of a scratch, which causes a local stress concentration and increases the ‘effective Kt’ at the scratch root, is the most significant factor in controlling fatigue performance. Scratches cause a decrease in crack initiation life, thereby reducing total component fatigue life. Compressive residual stresses induced by shot peening and the scratching process itself are beneficial to component life. Varying levels of scratch damage were fully characterised by scanning electron microscopy, microhardness testing and electron backscatter diffraction to show the severe microstructural modification and increased hardness caused by the scratching process. Computational modelling was carried out to determine geometrical effects of scratches on local stress and strain fields. The ‘effective Kt’ values under scratches were calculated, which helps to predict fatigue performance. This type of comprehensive investigation is important for damage tolerance lifing approaches and helps to minimise premature component retirement.

Field Assisted Sintering Technique (FAST) was used for the crystallisation of ionomer glasses and the production of the relevant glass ceramics. Extrusion was also used as an alternative processing method to produce honeycomb glass ceramics derived from similar glass compositions. Apatite-mullite glass ceramics derived from the general glass composition 4.5SiO\(_2\)-3A1\(_2\)O\(_3\)- 1.5P\(_2\)O\(_5\)-(5-x)CaO-xCaF\(_2\) can be produced by a lost wax method. However, Field Assisted Sintering Technique and Honeycomb Extrusion Technique are never used before and this present work presents the first data on the use of both of the above mentioned techniques. Calcium (Ca), Strontium (Sr) and Magnisium (Mg) containing glass powder compositions were produced and processed by FAST and Extrusion technique. X-ray diffraction of the materials produced by FAST showed the formation of a fluorapatite, mulite and a minor A1PO\(_4\) phase for the calcium glass. Sr-fluorapatite and Sr-aluminium silicate were formed in Sr glass and mullite and wagnerite were formed in Mg glasses. All the crystal phases formed were in good agreement with previous conventional crystallization studies. The FAST sintered glass ceramic properties were improved when compared with conventional sintering. In extrusion technique, the rheological properties were studied using Benow/Bridgwater model for paste parameters. Honeycomb extrusion pressure drop was also studied using a model developed by Blackburn and Bohm. In this study, we used waste glass to model the binder rehology of glass powder and modelled binder rheology in the apatite mullite glass. The measured paste parameters were in good agreement when compared with the experimental results. The produced honeycomb structure was sintered conventionally using a furnace. Microstructural studies and X-ray diffraction were carried out. The results of this studies show a well-defined porous structure and formation of crystal phases similar to the phases observed during conventional sintering.

This thesis is concerned with the fabrication and characterisation of lead free piezocomposites and transducers for use in high frequency medical ultrasound imaging applications. A water based gel casting and micro moulding approach has been developed to fabricate 1-3 composites with a random pillar structure in the lead free and lead based piezoelectric material. High frequency transducers incorporating the random composites as the active components have been fabricated, characterised and demonstrated in real tissue imaging environments. A water based gel casting system has been used incorporating Hydantoin Epoxy resin, amine hardener (Bis (3-aminoproply) amine) and dispersant. Viscosities of the 50BCZT and PZT systems were minimised by the addition of 2.4 and 1 wt% of dispersant respectively. The highest values of piezoelectric and dielectric properties corresponded to 50BCZT samples fabricated with a gel casting slurry incorporating 30 wt% resin and sintered at 1425 °C, with d33 and kp values of 330 pC/N and 0.43, respectively. 1-3 composites were successfully fabricated from the BCZT and PZT bristle block structures and only one resonance peak corresponding to the thickness mode was observed. PZT composites offered generally higher thickness coupling coefficients than 50BCZT composites, where the highest value of 0.78 was measured for samples sintered at temperature 1425 °C. Focused PZT, focused 50BCZT, unfocussed PZT and unfocussed 50BCZT transducers were successfully fabricated using the composites with randomised structure, and have operating frequencies of 35, 40, 50 and 35 MHz respectively.

The atmospheric corrosion of 304L and 3 16L austenitic stainless steels was investigated in conditions relevant to the storage of intermediate level nuclear waste (I L W). Thin electrolyte films were created via automated droplet deposition, allowing multiple tests to be conducted in parallel. In-situ monitoring of droplet arrays on stainless steel samples was conducted with the use of a flat-bed document scanner, allowing large-scale, automated monitoring of corrosion processes. The initiation time for individual corrosion processes was established, showing that corrosion was slower to initiate under less aggressive conditions, and allowing 'true corrosion site lifetimes to be recorded, and compared with their depths. The presence of precipitated species within an electrolyte film was shown to affect the corrosion processes within that film. Both NaCl precipitates and glass shards acted as barriers to ion transport. This affected both the propagation of corrosion, and the electrochemical potential within the droplets; a higher precipitate content decreased the average corrosion depth and the extent of corrosion. The presence of nitrate and sulphate salts, both known corrosion inhibitors in full- immersion conditions, was shown to inhibit atmospheric corrosion when the inhibitor:chloride ratio was above a certain value. This was independent of the absolute amounts of salts, but dependent on the exposure humidity of the test.

Ion irradiation has been investigated as a route for the preparation of mechanically stable and highly durable cross linked sulphonated PEEK for fuel cell application. The formation of cross linking was confirmed by solvent extraction using the well known Charlsby–Pinner equation. The DSC results indicated that the cross links retard the crystallization, but no changes were observed in the mechanism of crystallization. The thermal kinetic data for irradiated PEEK quantitatively suggest that these films still have sufficient thermal stability for long term applications as fuel cell membranes. Analysis of the dielectric response by Cole-Cole, Havrilak and Negami and Williams and Watts equations indicated that the dipole relaxation was broadened and becoming more asymmetric with cross link density. The sulphonation of the cross linked PEEK in concentrated sulphuric acid indicated that the rate of reaction decreased with cross linking density and was consistent with diffusion control kinetics. Increasing cross link density resulted in more bound water in the equilibrated membranes and the nano-structure present was comparable to that of Nafion. Cross linking improved the chemical stability of PEMs in particular in methanol solution.The measurement of power output and energy efficiency suggested that the cross linked PEMs produced are promising candidates to replace Nafion membranes but more information are required, in particular on their long term stability under fuel cell operating conditions.

The recovery of metals from secondary resources is increasing to alleviate supply risks associated with primary sources. Thermal plasma is widely used for platinum group metal recovery from automotive catalysts, but the mixing of various catalyst types makes their processing difficult. It was found that it was possible to separate silicon carbide based catalysts from cordierite based catalysts by a combination of magnetic and electrostatic separation processes resulting in a cordierite fraction of over 98 % purity, which would result in a more consistent feed material to the plasma process enhancing metal recovery. The flexibility of plasma means that the operational conditions in the furnace can be controlled to suit the chemistry of less noble metals such as rhenium and drive gas phase reactions. The technology was used to recover platinum and rhenium from spent petrochemical catalysts via a novel pyrometallurgical process with over 98 % recovery efficiencies of both metals. The plasma process produces a large amount of slag as a by-product which can be used in higher value applications to avoid waste and improve business models. Plasma derived slag was shown to be an effective, low carbon cement replacement which can potentially obtain a market value of £50/tonne.

The process of sheet metal forming is commonly used to create 3-D surfaces in, e.g., aircrafts and automobiles. Stamping is one of most common sheet metal forming processes but traditional forming processes which have been developed for mass production are inflexible and expensive, and economically unsuitable for small-scale production. More appropriate for small-batch and prototype production are flexible forming methods such as multi-point forming (MPF) which have been developed in recent years. A pair of opposed reconfigurable tools containing pin matrices could replace traditional solid stamping tools. Based on this technique, the construction of sheet metal forming tools becomes flexible and fast. Springback, caused by elastic recovery and release of residual stress, is an unavoidable issue in all sheet metal forming and significantly affects the geometrical precision of the products. Springback is a defect, and if it is beyond permissible tolerance it will adversely affect the assembly process such as distortion of sub-assemblies and poor fit-up during welding. Estimation of springback remains an important and challenging issue for the sheet metal industry. Based on the ABAQUS software, 3-D finite element models were generated, with the required constraints and boundary conditions described and applied in the simulation. The process of multi-point forming and springback were simulated by combining explicit and implicit algorithms. The influence of some significant working parameters, such as radius of forming curvature, blank holder force and elastic cushion thickness on final product quality (springback, thickness variation and wrinkling) has been investigated.

Experimental results and analyses have shown that significant improvements in coal grindability (reductions in Relative Work Index) can be achieved by exposing coals to microwave radiation. Experimental data have indicated that low rank coals are highly responsive to microwave radiation, possibly due to their higher inherent moisture content. There is evidence to suggest that gaseous evolution (water vapour and volatile matter) and localised zones of differential expansion (arising for example from occluded mineral matter) in coal during heating give rise to crack formation and hence are the probable causes for the measured increase in coal grindability. The composition of the various coals treated by microwave radiation remained relatively unaltered and there was no significant change in coal calorific value or the proximate and ultimate analyses (dry, mineral matter free basis). Initial (laboratory-scale) microwave trials and pilot-scale testwork demonstrated an improvement in the grindability of various coals. However, the gross energy input for these tests were excessively high (220k WhIt) in comparison to that used mechanically for pulverised coal production (15-20kWhlt). Improvements in microwave cavity design and increased electric field strengths may increase the energy efficiency of the process; however, further work would be required. Additional studies were carried out to evaluate the potential use of microwave technology for coal desulphurisation. The results were encouraging and show that substantial improvements in pyrite separation can be achieved with some coals. Fundamental studies have shown that there is significant change in coal flowability following microwave exposure.

Highly conductive (3.0 - 5.0 x 10 \(^{-4}\) \( \Omega\) cm) and transparent (80 – 85% ) ITO films were successfully fabricated on glass and polymer substrates (PET, PEN and PC) by pulsed laser deposition at low temperatures (24 – 150 °C). The influence of deposition conditions on the structural and physical properties of ITO-coated glass substrates was studied. The samples were investigated using Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), X-Ray Diffraction (XRD), the fourpoint probe and a spectrophotometer. Sol-gel derived ITO films dip-coated on glass substrates were also studied. The optimum film obtained at a firing temperature of 600 °C had a resistivity of 1.8 x 10 \(^{-2}\) \( \Omega\) cm, and optical transmittance of 80%. The electro-mechanical behaviour of ITO/polymer systems was investigated under uniaxial tension and controlled buckling in tension and compression. The resistance changes were monitored in situ. Cracking and buckling delamination failure modes were observed for all samples investigated at critical strains raging from 2.8 to 3.4%, and from 7.0 to 8.0%, respectively. The results showed that the dominant critical failure mode depends on the applied stress conditions. The ITO/PEN samples showed high flexibility; the samples were buckled in tension down to a 2.6 mm radius of curvature before cracks start to occur.