I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[614]
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Sep 2008
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I18-Microfocus Spectroscopy
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Abstract: The salt films formed on metal surfaces dissolving inside artificial corrosion pits formed in 1 M HCl have been probed with synchrotron X-ray diffraction. NiCl2 · 6H2O is the main phase in the salt film on nickel, whereas salt films on both iron and 316 L stainless steel are predominantly FeCl2 · 4H2O. However, the salt film on iron has a very fine homogeneous crystallite size whereas that on stainless steel is much coarser. The potential-dependence of the film formed on iron has been determined.
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Feb 2008
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I18-Microfocus Spectroscopy
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Jul 2007
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I18-Microfocus Spectroscopy
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Abstract: Core/shell Fe/Cu and Fe/Au nanoparticles were prepared directly by deposition from the gas phase. A detailed study of the atomic structure in both the cores and shells of the nanoparticles was undertaken by means of extended absorption fine structure (EXAFS) measurements. For Fe/Cu nanoparticles, a Cu shell ∼20 monolayers thick appears similar in structure to bulk Cu and is sufficient to cause the structure in the Fe core to switch from body centred cubic (bcc; as in bulk Fe) to face centred cubic. This is not the case for thinner Cu shells, 12 monolayers in thickness, in which there is a considerable contraction in nearest-neighbour interatomic distance as the shell structure changes to bcc. In Fe/Au nanoparticles, the crystal structure in the Fe core remains bcc for all Au thicknesses although there is some stretching of the lattice. In thin Au shells ∼2 monolayers thick, there is strong contraction in interatomic distances. There does not appear to be significant alloying at the Fe/Au interface.
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Sep 2010
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I18-Microfocus Spectroscopy
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Paul
Schofield
,
Andrew
Smith
,
Fred
Mosselmans
,
Hendrik
Ohldag
,
Andreas
Scholl
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Simone
Raoux
,
Gordon
Cressey
,
Barbara
Cressey
,
Paul
Quinn
,
Caroline
Kirk
,
Simon
Hogg
Abstract: This work describes the application of microfocus X-ray absorption spectroscopy (XAS) and X-ray photo-emission electron microscopy (XPEEM) to the study of the complex mineralogical intergrowths within the Santa Catharina meteorite. The Santa Catharina meteorite of this study (BM52283 from the meteorite collection of the Natural History Museum, London, UK) primarily comprises a taenite bulk host phase (Fe:Ni ratio = 70.9 ± 0.8%:29.1 ± 0.8%) with a set of oxide-bearing cloudy zone textured regions (Fe:Ni:O ratio = 40.4 ± 0.3%:49.0 ± 0.7%:10.6 ± 0.8% at the core and Fe:Ni:O ratio = 34.4 ± 1.5%:42.7 ± 0.6%:22.9 ± 1.8% towards the rims) and numerous schreibersite (Fe:Ni:P ratio = 38.6 ± 1.6%:38.4 ± 0.9%:23.0 ± 0.5%) inclusions. Between the schreibersite and the taenite are rims up to 50 μm across of Ni-rich kamacite (Fe:Ni ratio = 93.4 ± 0.4%:6.6 ± 0.5%). No chemical zoning or spatial variations in the Fe and Ni speciation was observed within either the schreibersite or the kamacite phases. The oxide-bearing cloudy zone textured regions mostly comprise metallic Fe-Ni alloy, predominantly tetrataenite. Within the oxide phases, the Fe is predominantly, but not entirely, tetrahedrally co-ordinated Fe3+ and the Ni is octahedrally co-ordinated Ni2+. Structural analysis supports the suggestion that non-stoichiometric Fe2NiO4 trevorite is the oxide phase. The trevorite:tetrataenite ratio increases at the edges of the oxide-bearing cloudy zone textured regions indicating increased oxidation at the edges of these zones. The spatial resolution of the XPEEM achieved was between 110 and 150 nm, which precluded the study of either the previously reported ∼ 10 nm precipitates of tetrataenite within the bulk taenite or any antitaenite.
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Jun 2010
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I18-Microfocus Spectroscopy
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Abstract: Thermal spraying is emerging as the leading route for the deposition of protective coatings onto engineering components to improve operation under extreme conditions of temperature, wear or corrosion. Detailed microstructural assessment is a key element in improving coating performance, and this study demonstrates the application of microfocus X-ray techniques to the determination of elemental and structural variations in the coatings.
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Oct 2010
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I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[1115]
Abstract: The influence of soil organisms on metal mobility and bioavailability in soils is not currently fully understood. We conducted experiments to determine whether calcium carbonate granules secreted by the earthworm Lumbricus terrestris could incorporate and immobilise lead in lead- and calcium- amended artificial soils. Soil lead concentrations were up to 2000 mg kg-1 and lead:calcium ratios by mass were 0.5-8. Average granule production rates of 0.39 + 0.04 mgcalcite earthworm-1 day-1 did not vary with soil lead concentration. The lead:calcium ratio in granules increased significantly with that of the soil (r2 = 0.81, p = 0.015) with lead concentrations in granules reaching 1577 mg kg-1. X-ray diffraction detected calcite and aragonite in the granules with indications that lead was incorporated into the calcite at the surface of the granules. In addition to the presence of calcite and aragonite X-ray absorption spectroscopy indicated that lead was present in the granules mainly as complexes sorbed to the surface but with traces of lead-bearing calcite and cerussite. The impact that lead-incorporation into earthworm calcite granules has on lead mobility at lead-contaminated sites will depend on the fraction of total soil lead that would be otherwise mobile.
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Feb 2011
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I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[1125]
Abstract: Disregulation of transition metal ions is implicated in many neurodegenerative disorders,
and altered status may both affect disease progression and hold biomarker potential. The analytical
challenges in this field often lead to isolated evidence for altered concentration, distribution, chemical or
mineral state, limiting the conclusions that can be drawn. Combining methods that are highly sensitive to
a range of these properties can give new insight.
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Mar 2011
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I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[4842]
Abstract: Timescales of magma chamber assembly and recharge are investigated here by applying 1D and 2D diffusion modeling techniques to high-resolution maps of titanium in quartz from a large-volume ignimbrite eruption in the Taupo Volcanic Zone, New Zealand. We compare quartz zonation patterns and associated diffusion timescales from the ?340?ka Whakamaru super-eruption (magma volume ?1000?km3) with the Younger Toba Tuff super-eruption, 74?ka (2000?km3), Sumatra, and the smaller volume ?50?ka Earthquake Flat eruption (10?km3), Okataina Caldera Complex, New Zealand. Two principal timescales are presented: that of chamber recharge and eruption triggering events, and that of magma generation (involving long-term assembly, stirring and reactivation). Synchrotron micro-X-ray fluorescence maps of core–rim quartz transects provide a high-resolution record of magma chamber conditions throughout quartz crystallization. Quartz crystals from the Whakamaru magma display complex zonation patterns indicating fluctuating pressure–temperature conditions throughout the crystallization history. Toba and Earthquake Flat, in contrast, display simple quartz-zoning patterns and record slightly longer periods of crystal residence in the chamber that fed the eruption. We apply Lattice Boltzmann 2D diffusion modeling to reconstruct the timescales of quartz crystal zonation, accounting for crystal boundary complexities. Quartz crystal orientation is also accounted for by using geometry constraints from the synchrotron data. Our calculations suggest that crystal-mush reactivation for the main Whakamaru magma reservoir occured over a period of the order of 103–104 years. Both the Earthquake Flat and Toba eruptions experienced a significant recharge event (causing a temperature and pressure change), which occurred within ?100 years of eruption. In comparison, the complex Whakamaru quartz zoning patterns suggest that the magma body experienced numerous thermal and compositional fluctuations in the lead-up to eruption. The final magma recharge event, which most probably triggered the eruption, occurred within ?10–60 years of the eruption. Even though the volume of these systems spans two orders of magnitude, there does not appear to be a relationship between magma volume and diffusion timescale, suggesting similar histories before eruption.
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Apr 2012
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I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[1793]
Abstract: Al3Ti, Al13Cr2 and Al13Fe4 are important intermetallics in a number of Al alloy systems including complex ultra-high-strength systems with excellent elevated-temperature performance. A full knowledge of their properties and crystallographic structures is a key factor for the understanding of these complex alloys. In the present study samples of the three pure intermetallics were prepared and regions of interest identified in a billet of Al93Fe3Cr2Ti2 alloys and 20 × 10 × 2 µm samples extracted utilizing a Focussed Ion Beam Transmission Electron Microscopy (FIB TEM) sample preparation technique. Using the microfocus spectroscopy beamline I18 at Diamond Light Source we were able to examine 5 µm sections of the samples using X-ray Diffraction (?-XRD) and Extended X-ray Absorption Fine Structure (?-EXAFS) in an attempt to describe the local structure of the second-phase particles and characterized the microstructure of the FIBed samples to selectively illuminate the different phases.
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Nov 2010
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