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Abstract: Fluid catalytic cracking (FCC) is the main conversion process used in oil refineries. An X-ray microscopy method is used to show that metal poisoning and related structural changes in the zeolite active material lead to a non-uniform core–shell deactivation of FCC catalyst particles. The study links the detrimental effect of V and Ni poisoning with zeolite destruction and dealumination in a spatial manner within a single FCC catalyst particle.

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Abstract: Laboratory and synchrotron X-ray fluorescence (XRF) have been used to investigate the microscopic and macroscopic distribution of metallic contaminants in membrane electrode assemblies (MEAs) which were used in proton exchange membrane fuel cell (PEM FC) stacks. The laboratory XRF results were consistent with the synchrotron XRF results. Higher levels of contaminants observed for the areas near to the coolant outlet than the areas near to the coolant inlet. The cathode side of MEAs showed higher levels of contamination than the anode side of the MEAs. Fe was the main contaminant, and there were also significant levels of Ni. Levels of Cu and Cr were significantly lower. Synchrotron XRF maps of the MEA cross sections generally showed higher levels of contaminants on the cathode side compared with the anode side. Fe was mainly observed in the cathode side microporous layers, whereas Ni, Cr and Cu were mostly accumulated in the cathode side or in the membrane. Synchrotron XRF maps of MEA plan views showed a crack-like distribution for Fe and Pt which were similar to cracks in the microporous layer of the MEAs. A novel electrochemical cell that simulated galvanic and crevice corrosion, temperature cycles for a PEM fuel cell, and pressure across the stacks was designed and used to discriminate between the corrosion behaviour of candidate coatings for bipolar plates.

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Abstract: It is well established that oxygen fugacity, fO₂ , is one of the key parameters that needs to be quantified in order to understand igneous processes, model the geophysical behaviour of the core and mantle, to understand the exchange of C-O-H-S gases between the atmosphere and the interior of the Earth, and to further our understanding of other terrestrial planets. Despite this it remains one of the most poorly constrained geochemical variables, limiting our understanding of terrestrial systems. Recent work has focused on using accessory minerals for determining magmatic fO₂ , as a probe to constraining conditions in planetary interiors. Accessory minerals are already important petrological tools for providing insight into magmatic conditions. These minerals may concentrate a variety of trace elements, and hence are crucial in understanding the elemental budget of magmas. Accessory minerals such as zircon and apatite are also some of the hardier minerals found in igneous rocks and are, therefore, less likely to be altered by processes such as chemical weathering, metasomatism or crustal anatexis. Furthermore, study of detrital accessory minerals in ancient sedimentary rocks could provide much needed insight into the evolution of the oxidation state of the early Earth. This work aims to assess how the compositions and structures of two accessory minerals, spinel and apatite, respond to variations in magmatic fO₂ and to determine whether these minerals could act as probes of fO₂ in planetary interiors. Focus has been concentrated on the element manganese, as (1) it is a relatively abundant trace element, (2) it can exist in valence states from Mn²⁺ to Mn⁵⁺ in nature, and (3) recent work has suggested that Mn may become preferentially concentrated in apatite under reduced conditions. In an initial investigation, large single crystals of Mn-rich spinel were synthesised under a variety of fO₂ conditions. X-ray absorption near edge structure (XANES) spectroscopy and structural refinements of single crystal X-ray diffraction data were used to determine Mn valence state and coordination. Results show that Mn is present in spinel as both Mn²⁺ and Mn³⁺, distributed over both octahedral and tetrahedral cation sites. However, in contrast to the Fe⁺²/Fe³⁺ ratio, little variation in Mn valence as a function of fO₂ was observed. Results were, however, useful in testing and refining protocols for modelling Mn XANES data in a simple, model system. In contrast to results from spinel, previous studies have indicated that Mn valence may change significantly in the accessory mineral apatite due to variations in magmatic fO₂ .

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Abstract: We review our work to grow single-crystal silicon materials within the cores of optical fibers. Particular focus is placed on laser-induced crystallization methods that allow for precise control of the fiber's optoelectronic properties.

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Abstract: The sol-immobilisation method, in which metal nanoparticles are ‘preformed’ (stabilised by the polymer, polyvinyl alcohol) before they are anchored to a support material, was adapted in order to prepare monometallic Au/TiO2 and Pd/TiO2 catalysts, with tailored properties. Varied temperature and solvent environments (H2O, mixed H2O:EtOH and EtOH) were employed during colloidal metal formation, generating metal particles with distinct characteristics (metal particle diameter and available metal sites). The metal nanoparticle properties in the resulting catalysts were fully characterised using a range of spectroscopic (XAFS, IR and UV-Vis) and imaging techniques (TEM and HAADF STEM). It was determined that the preparation of metal nanoparticles at −30°C, in a mixed H2O:EtOH solvent afforded the smallest average particle diameter, regardless of the choice of metal (2.0 nm for Au, 1.4 nm for Pd). However, when prepared at 1°C in H2O, a higher population of small Au (< 5 atoms) or Pd clusters (< 20 atoms) existed, compared with any other environment. The performance of the catalysts were tested in three different reactions; Au/TiO2 for the oxidation of glycerol, and Pd/TiO2 for the hydrogenation of furfural and pnitrophenol. For the two former reactions, it was established that metal particle size is not the only factor influencing performance; the highly active isolated metal clusters, as well as the solvent-PVA-metal interaction, are considered very important factors, and are discussed. Understanding colloidal metal formation, including nucleation and growth phenomena, is vital in the future design of metal nanoparticle properties, and was investigated by means of in situ XAFS. A continuous flow method of nanoparticle synthesis was first explored and developed, before a synchrotron based experiment was performed to monitor the nanoparticle generation (colloidal reduction) in a range of reactors fabricated from different materials (silicon/glass, PTFE and PEEK).