This thesis evaluates the utility of a geochemical technique for the investigation of palaeoenvironmental change in south west England. The method, EDMA (Energy Dispersive X-ray Micro Analysis), is a rapid, non-destructive analysis tool, capable of detecting a large range of geochemical elements. This research examines the most appropriate method of sample preparation for organic soils and peats, and investigates the reliability of results gained from EDMA with respect to conventional bulk geochemical techniques. A detailed study focused on a range of different sedimentary sites in south west England where a variety of palaeoenvironmental changes were thought to occur. Pollen analysis was undertaken on the same sedimentary material, and provided complementary information on the nature and scale of vegetation change through time. Sediments from a coastal valley mire near North Sands, Salcombe, revealed information relating to the processes of sea-level change in this part of south Devon and the subsequent autogenic processes as the sediment accumulated through time. A range of sites were located on the granitic upland of Dartmoor. A raised bog, Tor Royal, provided data relating to the changing nature of the central upland landscape from late Mesolithic times to the present day. Two soligenous sites, Upper Merrivale and Piles Copse, sought to investigate the activities of postulated anthropogenic activity at a much smaller spatial scale, with particular interest placed upon the evidence for deforestation activity and the utilisation of the local mineral resources. The last site, Crift Down, a lowland spring fed valley mire utilised geochemical and palynological fluxes within the peat to investigate processes and activities associated with archaeological evidence for Medieval tinworking in this area of Cornwall. The results from the EDMA investigations, and comparable studies using other geochemical methods including EMMA, AAS and flame photometry, suggest the technique to have greatest applicability as a first stage tool in the analysis of general activities of past environmental change. The technique was found to yield reliable results for the major elements (Si, Al, 5, Fe, Ca, K, Na and Mg), but is generally incapable of providing useful data on heavy metal elements. The data from south west England suggest the method to reflect activity at a range of different scales, and as part of a structured programme of analysis may contribute information to allow a more holistic environmental reconstruction to be made.

Ternary indium aluminum nitride (InXAl1-XN) semiconductor is an attractive material with a wide-range bandgap energy varied from ultraviolet (Eg(AlN): 6.2 eV) to near infrared (Eg(InN): 0.7 eV). With tuning composition, it can be widely used to many optoelectronic device applications. In this thesis, I have studied InXAl1-XN film deposited on Si (111) substrate using natural and isotopically enriched nitrogen as reactive gas by reactive magnetron sputter epitaxy (MSE). Four series of experiments were performed, which are I. InAlN presputtering, II. InAlN sputter deposition, III. InAlN direct deposition, and IV. InAlN direct deposition using isotopically enriched nitrogen. The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDX). The θ-2θ XRD scan confirms that the designed composition x = 0.17 of InXAl1-XN film was obtained. TEM images shows that an amorphous interlayer with a thickness ranging from 1.2 nm to 1.5 nm was formed between Si substrate and InXAl1-XN film. However, high-resolution TEM shows that the interlayer actually contains partial crystalline structures. EDX line profile indicates that the chemical composition of the amorphous interlayer is silicon nitride (SiNX). By comparing d-spacing measurement of partial crystalline structures with EDX line profile, it reveals that partial SiNX crystal is formed in the interlayer. Nonetheless, the samples (IAD01, IAD02, IAD03, IAD04), grown without presputtering procedure, contain both crystalline SiNX and InXAl1-XN embedded in the amorphous interlayer. It means that SiNX and InXAl1-XN film can be directly grown on the substrate in the beginning of deposition. Moreover, the samples (IAD01, IAD03), quenched directly after deposition, have less crystalline structures in the interlayer then the samples (IAD02, IAD04), maintained at 800℃ for 20 min.

The observation of graphene’s extraordinary electrical properties has stirred great interest in two dimensional (2D) materials. The rapid pace of discovery for low dimensional materials with exciting properties continue with graphene allotropes, multiple polymorphs of borophene, germanene, and many others. The future of 2D materials goes beyond synthesis and characterization of free standing materials and on to the construction of heterostructures or sophisticated multilayer devices. Knowledge about the resulting local structure and composition of such systems will be key to understanding and optimizing their performance characteristics. 2D materials do not have a repeating crystal structure which can be easily characterized using bulk methods and therefore a localized high resolution method is needed. Electron microscopy is well suited for characterizing 2D materials as a repeating coherent structure is not necessary to produce a measureable signal as may be the case for diffraction methods. A unique opportunity for fine local scale measurements in low dimensional systems exists with a specific class of materials known as ferecrystals, the rotationally disordered relative of misfit layer compounds. Ferecrystals provide an excellent test system to observe effects at heterostructure interfaces as the whole film is composed of interdigitated two dimensional layers. Therefore bulk methods can be used to corroborate local scale measurements. From the qualitative interpretation of high resolution scanning transmission electron microscope (STEM) images to the quantitative application of STEM energy dispersive X-ray spectroscopy (EDX), this thesis uses numerous methods electron microscopy. The culmination of this work is seen at the end of the thesis where atomically resolved STEM-EDX hyperspectral maps could be used to measure element specific atomic distances and the atomically resolved fractional occupancies of a low dimensional alloy. These local scale measurements are corroborated by additional experimental data. The input of multiple techniques leads to improved certainty in local scale measurements and the applicability of these methods to non-ferecrystal low dimensional systems.

The field of X-ray imaging and X-ray diffraction have been combined in a new technique called Tomographic Energy Dispersive Diffraction Imaging (TEDDI). This diffraction imaging technique allows 3D sample images to be obtained, non-destructively, where each imaged point contains the atomic structural information associated with its diffraction pattern. The main drawback of the TEDDI technique is the long collection times needed to produce the images. In order to overcome this obstacle the rapid TEDDI (rTEDDI) system has been developed at the University of Manchester's Material Science Centre. The research and development of rTEDDI has been the focus of this PhD thesis. A proof of concept for the rTEDDI imaging technique was obtained using thin samples on station 7.6 SRS Daresbury. In this case a first generation array collimator was used in conjunction with an energy resolving Si pixelated detector. Structural information such as lattice parameters, crystal system and phase identiffcation were obtained for metal, polymer and deer antler bone samples. The use of high Z semiconductor detector material was investigated in order to increase the potential of TEDDI for larger and more dense samples. To enable penetration of larger samples high energy X-rays needed to be utilized. In order to detect these higher energies with a good efficiency the detector media was changed from Si to CdZnTe (CZT).The second generation rTEDDI, using CZT as the detection media, was intended to be used under high flux/high energy synchrotron radiation conditions. Testing of the system under these conditions on station 16.3 SRS Daresbury showed an inability to produce diffraction imaging. An in depth investigation into detector and collimator array performance showed a two fold cause. The ERD2004 detector was unable to handle the high countrates experienced during high flux/high energy synchrotron radiation conditions. The MK1.2 collimator array was found to become partially transparent to X-ray energies around the absorption edge of W resulting in the swamping of the diffraction signal under high flux/high energy synchrotron radiation conditions. A new detector Application Specific Integrated Circuit (ASIC) design, developed by the detector division and the Rutherford Appleton Laboratory, and Data Aquisition (DAQ) system, developed by Aspect Systems, as well as a number of new collimator array designs were developed and tested. Testing of the new collimator array structures have shown positive results and the new HEXITECdetector which was designed to be able to handle high countrates, have shown an unprecedented inter pixel uniformity and energy resolution which have been attributed to the ASIC performance and the use of better quality CZT material.

The aim of this thesis is to investigate the methodology of three dimensional chemical imaging of nanoparticles through the use of scanning transmission electron microscope (STEM) – energy dispersive X-ray (EDX) spectroscopy. In this thesis, an absorption correction factor is derived for spherical nanoparticles that can correct X-ray absorption effects. Quantification of EDX spectra of nanoparticles usually neglects X-ray absorption within the nanoparticle but may lead to erroneous results, thus an absorption correction is important for accurate compositional quantification. The absorption correction presented is verified through comparison with experimental data of Au X-ray peaks in spherical Au nanoparticles and is found to agree excellently. This absorption correction allows accurate compositional quantification of large ( > 100 nm) particles with STEM-EDX.Three dimensional chemical mapping is achievable through the use of EDX spectroscopy with electron tomography. Here, the methodology of STEM-EDX tomography is fully explored, with a focus on how to avoid artefacts introduced through detector shadowing and low counts per pixel. A varied-time acquisition scheme is proposed to correct for detector shadowing that is shown to provide a more constant intensity over a series of projections, allowing a higher fidelity reconstruction. The STEM-EDX tomography methodology presented is applied to the study of AgAu nanoparticles synthesized by the galvanic replacement reaction. The elemental distribution as a function of the composition of the as-synthesized nanoparticles is characterised and a reversal in the element segregated to the surface of the nanoparticles is found. The composition at which the reversal takes place is shown to correlate with a peak in the catalytic yield of a three component coupling reaction. It is hypothesized that a continuous Au surface results in the optimum catalytic conditions for the reaction studied, which guides the use of galvanically prepared AgAu nanoparticles as catalysts.

Electric and hybrid vehicles uses regenerative braking, where application of the brake triggers the electric motor to work as a generator to produce electricity, which in turn charges the battery. This results in much less use of the friction brake, changing the corrosion and wear behavior of the rotor surface. There is a need for research on this topic, since fully electric or hybrid vehicles are replacing combustion engines due to concerns about global warming and climate change. Here the corrosion behavior of coated cast iron vehicle rotors in 3.5wt% NaCl is studied. The corrosion study has been performed using electrochemical methods such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). All the coated samples were provided by Pure Forge Rotors. Based on the results from SEM and EDX, the coating is atomic forge proprietary coating, and the base material is gray cast iron. Our primary objective is to study the corrosion behavior of coated, non-coated and friction-tested samples. CV experiments indicate a shift in the corrosion potential and corrosion current density due to changes in the nature of the exposed surface. Cross-sectional SEM showed the thickness of the coating to be 16-23 µm. After friction testing, the friction layer created by rubbing the brake pad over the rotor plays a role in corrosion resistance, but this depends on the type of brake pad material (i.e. semi-metallic, non-asbestos organic and low metallic). Results showed that friction film that forms after testing against non-asbestos organic pads provides the highest corrosion resistance amongst the three brake pad materials.

No / Solvent influences on the crystallization of polymorph and hydrate forms of the nootropic drug piracetam (2-oxo-pyrrolidineacetamide) were investigated from water, methanol, 2-propanol, isobutanol, and nitromethane. Crystal growth profiles of piracetam polymorphs were constructed using time-resolved diffraction snapshots collected for each solvent system. Measurements were performed by in situ energy dispersive X-ray diffraction recorded in Station 16.4 at the synchrotron radiation source (SRS) at Daresbury Laboratory, CCLRC UK. Crystallizations from methanol, 2-propanol, isobutanol, and nitromethane progressed in a similar fashion with the initial formation of form I which then converted relatively quickly to form II with form III being generated upon further cooling. However, considerable differences were observed for the polymorphs lifetime and both the rate and temperature of conversion using the different solvents. The thermodynamically unstable form I was kinetically favored in isobutanol and nitromethane where traces of this polymorph were observed below 10°C. In contrast, the transformation of form II and subsequent growth of form III were inhibited in 2-propanol and nitromethane solutions. Aqueous solutions produced hydrate forms of piracetam which are different from the reported monohydrate; this crystallization evolved through successive generation of transient structures which transformed upon exchange of intramolecular water between the liquid and crystalline phases

Trapping centres and their distributions in as-grown TlGaSeS layered single crystals were studied using thermally stimulated current (TSC) measurements. The investigations were performed in the temperature range of 10&ndash / 160 K with various heating rates between 0.6&ndash / 1.2 K/s. Experimental evidence has been found for the presence of three electrons trapping centres with activation energies 12, 20, and 49 meV and one hole trapping centre located at 12 meV. Their capture cross-sections and concentrations were also determined. It is concluded that in these centres retrapping is negligible as confirmed by the good agreement between the experimental results and the theoretical predictions of the model that assumes slow retrapping. The optical properties of TlGaSeS layered single crystals have been investigated by measuring the transmission and the reflection in the wavelength region between 400 and 1100 nm. The optical indirect transitions with a band gap energy of 2.27 eV and direct transitions with a band gap energy of 2.58 eV were found by analyzing the absorption data at room temperature. The rate of change v of the indirect band gap with temperature was determined from the transmission measurements in the temperature range of 10&ndash / 300 K. The oscillator and the dispersion energies, the oscillator strength, and the zero-frequency refractive index were also reported. The parameters of monoclinic unit cell and the chemical composition of TlGaSes crystals were found by X-ray powder diffraction and energy dispersive spectroscopic analysis, respectively.

Concrete, due to its low cost, durability and fire resistance, is one of the world’s most widely used construction materials. Concrete is typically reinforced with steel bars and welded wire mesh. Since the cost of steel is increasing and steel corrosion is a significant contributor to structural failure, it is advantageous to find an alternative replacement reinforcement material which can not only replace the steel, but also resist corrosion. Over the past few decades, polymeric fibres have been used as concrete reinforcement. The chemical bond between the polymeric fibre and the cementitious matrix is an important factor in the fibre’s performance as a concrete reinforcement. Despite the great importance of the chemical bonding at the polymeric fibre/concrete interface, the chemical bonding at the interface is not well understood. To investigate the chemical interactions between polymeric materials and concrete, model systems of polymeric powder/white cement and polymeric fibre/white cement were chosen, where white cement was chosen for its suitability for nuclear magnetic resonance (NMR) experiments. The chemical interactions between poly(ethylenevinyl acetate) (EVA), poly(ether imide) (PEI), and poly(vinylidene fluoride) (PVDF) polymeric powders were studied via 13C NMR spectroscopy. It was found that EVA admixture undergoes hydrolysis in a cementitious matrix and follows a pseudo-second order kinetics model up to 32 days of cement hydration. PEI was also found to undergo hydrolysis at the imide functional group in a cementitious matrix. PVDF powder undergoes dehydrofluorination in the cementitious environment, producing a brown coloured polymer which is a result of conjugation of the polymer backbone. The interfacial transition zone between fluoropolymeric powder/white cement and steel and polymeric fibres (high density polyethylene/polypropylene, poly(vinyl alcohol), PEI, PVDF, and Nylon 6.6) was studied at short range using 19F, 27Al, and 43Ca NMR spectroscopy and at long range using the scanning electron microscopy/energy dispersive spectroscopy method. It was concluded that the chemistry of polymeric fibres themselves can alter the surrounding interfacial transition zone such that the calcium silicate hydrate favours a tobermorite or jennite-like structure, which could contribute to a strong or weak interface.

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