In Europe, the rapidly growing thermosetting foam insulation products industry comprises over 11,500 companies employing over a third of a million people and is worth about 6 billion Euros in trade. It is currently estimated 4-7 % of total new UK production is scrapped and goes to landfill. Estimated costs of disposing of this waste foam are of the order of £20 million/annum to the producers of foam panels and insulation blocks. A new strategic direction for rigid polymeric foams waste management has been developed converting the scrapped thermosetting foams into high added value material that can be used in various applications such as fire resistant insulating applications. Thus by this new innovative recycling process the waste is not only eliminated but benefits can be gained from the new material that comes out of it as a structural composite panel. The project involves a new concept that mixes fragmented scrap thermosetting foams materials with a proprietary liquid that cures at ambient temperature to form an incombustible material capable of withstanding high temperatures >1000 C. In this research different kind of polymeric foams used for manufacturing of reconstituted recycled samples. Sodium silicate solution has been chosen as the binder to binds shredded foams together. Due to fastening of sodium silicate curing different kind of acidic powders have been tested. For increasing of post properties after curing variety of fillers as an additive have been tried through out this research. Different foam cutting methods have been tested to find the suitable shredding routine. Rationale for selection of generic binder and its hardeners/fillers has been discussed in this project. Also as post properties evaluation compressive strength, thermal resistance, fire resistance and acoustic properties of recycled structural composite panels have been measured. At last a model for thermal conductivity of composite panels is developed.

TiO2 is widely considered as a promising photocatalyst to degrade various organic pollutants in water, and to harvest sunlight renewable energy application. However, the efficiency of the photocatalytic reaction using TiO2 is not high due to its wide band-gap (3.22 eV, corresponding to the wavelength of 385 nm), which corresponds to the lower end of the wavelengths of solar light. The aim of this project is to use a continuous hydrothermal flow synthesis (CHFS) technique and other post-treatment methods to synthesize and tailor nano-TiO2 and TiO2-related photocatalysts for improved photoactivity. It was demonstrated that the rapid crystallising environment in a CHFS system resulted in the anatase phase of TiO2 (ca. 5 nm) with a high surface area and a high crystallinity. The CHFS system provides a flexible route of doping TiO2 at the atomic level (lattice doping) either to decrease the band-gap or to introduce intra-band gap states, which allow activation by visible-light. The structures of the resulting nanocatalysts were investigated using powder X-ray diffraction (XRD) and Raman spectroscopy. The quantity and chemical nature of the catalyst surface were determined by X-ray photoelectron spectroscopy (XPS). Morphologies of the products were characterized by Transmission Electron Spectroscopy (TEM) and Scanning Electron Spectroscopy (SEM). Band-gap energy was determined by UV-Vis spectrophotometry. A TiO2-CeO2 composite catalyst was successfully synthesized by CHFS. A stable solid-solution was indentified, which leads to a totally different optical property (i.e. with a narrow band-gap) when mixed with a methylene blue (MB) dye solution. All the composites materials show improved photodecolourisation rates. Novel 2D sodium titanate nano-sheets (ca. 400×500 nm) were developed with a high concentration of NaOH into the reactor. This material exhibits the highest photocatalytic efficiency amongst all materials being tested in this project. Several post-treatment methods were also adopted to further modify the CHFS-prepared nano-TiO2 samples. By heat-treating nano-TiO2 powder in air, the crystallinity of the sample was increased. By exposing the nano-TiO2 to ammonia atmosphere at a range of temperatures, products ranging from N-doped anatase TiO2 to phase-pure titanium nitride (TiN) were successfully obtained. N-doped TiO2 materials showed significant red-shift in band-gap. Surface modification of TiO2 in vanadium salt leads to a high surface absorbability and photo-oxidising power. Among all the modified samples, some of them indeed exhibited improved photocatalytic activity over the unmodified nano-TiO2. Moreover, the microwave dielectric properties of selected TiO2 samples (metal ion lattice doped) were also examined using sintered TiO2 discs. The results suggest that a useful dielectric resonator material can be achieved by introduction of certain dopants in combination with a spark plasma sintering (SPS) method.

The room temperature sol-gel processing technique was employed for the first time in the present work to fabricate the novel binary compound of the calcia-alumina (C12A7) system consisting of calcium oxide (CaO) and aluminium oxide (Al2O3) in a 12:7 ratio. The highest level of homogeneity and transparency of the C12A7 solution in ethanol was achieved by optimizing pH values, reaction dynamics and modified precursor structures. Studies were performed on this binary oxide in both thin film and powder forms. By using High Temperature X-Ray Diffraction (HTXRD) and Simultaneous Thermal Analyzer (STA), phase transformations in C12A7 powder were examined in situ under continuous heat treatment from room temperature to 1200°C. The samples were found to be amorphous at room temperature. As the temperature was increased, crystallisation was completed at 1100°C. The purity of C12A7 and the removal of redundant chemical by-products were confirmed by independent Fourier Transform InfraRed (FTIR) and Raman Spectroscopic measurements. C12A7 thin films were spin coated on single crystal MgO <100> substrates and the effect of heat treatment on crystallinity were investigated using XRD. Initial signs of the crystallisation of C12A7 thin film were observed at 800˚C and the complete crystallisation was achieved on heat treatment at 1100°C for 3 hours. Optical absorption spectroscopy measurements were made in the UV-Visible region and experimental data were analyzed to evaluate the dependence of the band structure of C12A7 crystalline phase on annealing temperature.

Offshore wind farm structures may have the potential to affect marine navigation and communication systems by reflecting radar signals. With ever increasing size of wind turbines it is necessary to better understand the influence of radar signals on wind turbine blades in order to minimise the radar reflecting potential. One possible way of reducing radar reflection is to use radar absorbing materials. In this thesis, epoxy composite materials reinforced with five different types of nano-size additives: carbon nanotubes (CNTs), carbon blacks (CBs), silver, tungsten carbide and titanium oxide are manufactured and tested to investigated their potential as wind turbine blade material that absorb radar signals. Nanoadditives/epoxy composites with additives content ranging from 0.05-1 wt. % were fabricated by a simple cast moulding process. The nanoadditives were dispersed in the epoxy resin by sonication method. The degree of nanoadditives dispersion was observed by examining the surface of the composite materials using scanning electron microscope (SEM). Complex permittivity of the nanoadditives/epoxy composites was studied using a free wave transmittance only method at a frequency range of 6.5-10.5 GHz. The effect of the percolation threshold of the direct current conductivity on the composite permittivity was analysed and discussion. In order to get a better insight in the importance of the results they were compared to existing models (Maxwell- Garnett, Bruggeman, Bottcher, Lichtenecker and Lichtenecker-Rother). A new model based rule of mixtures is developed to predict the complex permittivity of the composite. A model of wind turbine rotor blade made of the nanoadditives/epoxy composite was developed using Comsol-multiphysics software. The data obtained from the experimental work was inputted in to the model to generate result of backscattered energy verses composite permittivity as a function of nanoadditives content. A decrease in backscattered energy was noticed with increasing nanoadditives content. The results demonstrate that radar reflecting signals will be significantly reduced by incorporating nanoadditives in the composite materials.

Gas sensors based on different principles have been developed for the applications of environmental monitoring, industrial processing, aerospace and the human body. Carbon nanotubes (CNTs) demonstrate a detectable electrical properties change upon gas molecules absorption. This has been extensively studied and used in chemiresistors and chemical field-effect transistors. Simultaneous response to different types of gases was reported. The aim of this study is to develop a new type of gas sensor by replacing the gate metal of a field-effect capacitor with a carbon nanotubes network. This novel sensor will combine resistivity measurements with potentiometric measurements, which should ideally lead to increased functionality and selectivity. The substrates (Al/Si/SiO2/Si3N4 or Al/Si/SiO2/Si3N4/LaF3) were fabricated with two gate electrode structures (interdigitated and two-line). CNTs in different solvents were drop or spray coated on to the substrates. Platinum coating on the CNTs was also introduced. The resistive measurements indicated an increase in the resistance of CNTs networks with increased oxygen concentration, and a decrease in the resistance of CNTs networks with increased hydrogen concentration with humidity interference. Evenly distributed CNTs film was achieved by spray coating which allowed the use of CNTs network as gate materials for potentiometric measurements. The potentiometric measurements suggested that the C-V curve shifted towards a lower voltage with an increased hydrogen concentration, and a higher voltage with an increased oxygen concentration. However, the response time was too long for practical applications. Pt deposition significantly improved the hydrogen response rate. A voltage shift of -450 mV with an equilibration time of 2 minutes was achieved when the hydrogen concentration increased from 1 to 100%. The C-V curve shifted by 500 mV with increased oxygen concentration (1-100%).

Composites are normally composed of two distinct phases: reinforcement and matrix. In recent years, a new class of “self-reinforced” polymer composites or “all-polymer” composites, which are based on similar or identical materials for both reinforcement and matrix have generated increasing interests in both academia and industries due to their advantages in terms of processing, interfacial properties and recyclability. Current research trend in this field is to investigate the potential possibilities of all-polymer composites based on high-performance polymer fibres. In this thesis, all-poly(ethylene terephthalate) composites (Part 1) and all-aramid composites (Part 2) were prepared. In Part 1, Chapter 3 describes the melt spinning and drawing of poly(ethylene terephthalate) (PET) into highly oriented fibres, with moduli of 20GPa and tensile strengths of 925MPa. The effects of spinning and drawing conditions on the mechanical properties of PET fibres were studied. In the following Chapters 4 and 5, all-PET composites were prepared from 1) hot compaction of bi-component multifilament PET yarns; and 2) a film stacking technique, i.e. combining PET tapes unidirectionally with copolyester adhesive films in an alternating “brick-wall” layer-by-layer structure. The effects of processing conditions on mechanical properties were investigated. In Part 2 Chapter 7, all-aramid composites were prepared by a selective surface dissolution method where aramid fibres were partially dissolved to form a matrix phase to bond remaining fibres together into composites. The structure, morphology and mechanical properties were characterized by X-ray diffraction, scanning electronic microscopy, dynamic mechanical analysis and tensile testing. Compared to traditional aramid/epoxy composites, these all-aramid composites show significantly high mechanical properties, even at elevated temperatures. In Chapter 8, the effects of processing conditions on various properties of all-aramid composites were studied and an optimum condition was found. By replacing high concentration sulphuric acid as a solvent, a mild mixed solvent was used to dissolve aramid fibre surfaces in Chapter 9. In this way, all-aramid composites with prolonged immersion times were prepared and characterized. Potential future work including all-PET composites from post-consumer PET waste, microstructural characterization of all-aramid composites and woven all-aramid composites are discussed in Chapter 10.

A comprehensive study of domain switching process in different ferroelastic and ferroelastic/ferroelectric perovskite structured ceramics has been performed. The effects of thermal fluctuations on domain switching dynamics were investigated in the ferroelastic and in the ferroelectric case under static and dynamic electric and mechanical conditions. In the ferroelastic case, domain switching behaviour was investigated for different compositions, using different types of mechanical tests. Compression tests were carried out to characterize the ferroelastic properties, such as coercive stress, hysteresis loop and irreversible strain. Creep experiments were performed to study the domain switching time dependence at different stress levels. Domain switching kinetics during creep was characterized by implementing a rate model, based on thermal activation rate theory, which allowed the activation volume to be estimated. A Rayleigh-type analysis was performed to study the effects of stress amplitude, loading rate, temperature and composition on ferroelastic switching. Rayleigh-type relationships were proposed to fit the results and the rate model developed was applied to quantify the effect of the loading rate on the Rayleigh loops. Alternative methodologies were developed to assess the effects of rate and temperature on the coercive stress, providing original sets of data. A further application of the rate model provided an estimation of the activation parameters (volume and enthalpy). In PZT 5A at the coercive field the activation volume was calculated to be 2.44 nm3, with a reasonable consistency with the value obtained from creep tests (7.49 nm3). In the ferroelectric case, domain switching was studied by generating P-E and butterfly hysteresis loops and by analysing creep-relaxation curves. In creep experiments, the polarization and the strain were measured simultaneously, during the application of a constant electric field. An insight into the evolution of domain structure and on domain switching mechanisms was gained, highlighting analogies and differences with the ferroelastic case. Experiments at different frequencies, allowed the activation volume to be estimated at the coercive field (77 nm3). The relatively large value indicates small rate dependence and suggests a domain structure with broad and mobile domain walls, being the preferred sites for the nucleation.

This thesis investigates both experimentally and numerically the oxidation, sintering, melting and solidification processes of different nanoparticles under various thermodynamic scenarios, with a background for energy applications. Two sets of main techniques are adopted in this work, which are isoconvensional kinetic analysis and molecular dynamics simulation. Based on the techniques of simultaneous Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC), for first time the isoconvensional kinetic analysis is applied to study the oxidation of nickel and tin nanoparticles. This method is demonstrated capable of modelling one-step nanoscale oxidation and revealing underling kinetic mechanisms. Moreover, some distinct features of nanoparticle oxidation compared with their bulk counterparts are found such as melting depression, oxidation kinetic change in the vicinity of Curie point of nickel and pressure-related two-step oxidation of tin nanoparticles. The detailed study from Molecular Dynamics (MD) simulation establishes a three-stage sintering process of two nickel nanoparticles, which is unable to be described by bulk continuum-level models. MD is applied to study the interaction between nickel and aluminium and its consequent thermo-mechanical and structural property evolution in a nickel-coating aluminium particle in a heating and cooling cycle. The simulation successfully predicts the atomic diffusion during melting and the formation of glass and crystal phases, and allows for the estimation of interior core-shell pressure. Reactive MD is then applied to simulate the oxidation of silicon nanoparticles. It predicts well the exothermal reaction process and experimentally reveals the oxygen exchange process.

In materials science, the traditional methodological framework is the identification of the composition-processing-structure-property causal pathways that link hierarchical structure to properties. However, all the properties of materials can be derived ultimately from structure and bonding, and so the properties of a material are interrelated to varying degrees. The work presented in this thesis, employed artificial neural networks (ANNs) to explore the correlations of different material properties with several examples in different fields. Those including 1) to verify and quantify known correlations between physical parameters and solid solubility of alloy systems, which were first discovered by Hume-Rothery in the 1930s. 2) To explore unknown crossproperty correlations without investigating complicated structure-property relationships, which is exemplified by i) predicting structural stability of perovskites from bond-valence based tolerance factors tBV, and predicting formability of perovskites by using A-O and B-O bond distances; ii) correlating polarizability with other properties, such as first ionization potential, melting point, heat of vaporization and specific heat capacity. 3) In the process of discovering unanticipated relationships between combination of properties of materials, ANNs were also found to be useful for highlighting unusual data points in handbooks, tables and databases that deserve to have their veracity inspected. By applying this method, massive errors in handbooks were found, and a systematic, intelligent and potentially automatic method to detect errors in handbooks is thus developed. Through presenting these four distinct examples from three aspects of ANN capability, different ways that ANNs can contribute to progress in materials science has been explored. These approaches are novel and deserve to be pursued as part of the newer methodologies that are beginning to underpin material research.

The conventional materials discovery is a kind of empirical (“trial and error”) science that of handling one sample at a time in the processes of synthesis and characterization. However, combinatorial methodologies present the possibility of a vastly increased rate of discovery of novel materials which will require a great deal of conventional laboratory work. The work presented in this thesis, involved the practice of a conceptual framework of combinatorial research on BaTiO3-based positive temperature coefficient resistor (PTCR) materials. Those including (i) fabrication of green BaTiO3 base discs via high-throughput dip-pen printing method. Preparation and formulation of BaTiO3 inks (selection of dispersant and binder/volume fraction) were studied. The shape of drying residues and the morphogenesis control of droplet drying were discussed. (ii) investigation of a fast droplet-doping method, which induced the dopant precursor solution infiltrating into the porous BT base disc. Various characterization methods were used to examine the dopant distribution in the body of disc. (iii) devising a high-throughput electrical measurement system including an integrated unit of temperature control and automatic measurement operation, and an arrayed multichannel jig. (iv) synthesis of donor-doped BaTiO3 libraries, which involved lanthanum, erbium, yttrium as donor elements and manganese as an acceptor dopant element respectively. Their temperature dependant resistivities were also explored. The work successfully developed an integrated tool including high-throughput synthesis of a large batch of libraries and high-throughput electrical property measurement for combinatorial research on BaTiO3-based PTCR ceramics. The Abstract ii combinatorial method, thus validated, has the potential to deliver dopant-doped BTbased PTCR libraries rapidly with a very wide range of dopant mixtures and concentrations for electrical property measurement and deserves to be applied to other low level dopant ceramic systems. These approaches are novel and paving the way for other new materials selection and materials research.