I18-Microfocus Spectroscopy
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Abstract: The Moa Bay NiCo laterite deposits, placed in the so-called MayariBaracoa ophiolitic belt (eastern Cuba), are oxide type. Despite its geological relevance and economical impact no detailed studies exist with regards to cristallochemical characterization of Ni incorporated in (or attached to) the main Ni-containing minerals forming the lateritic profile. A sample corresponding to the ore limonite horizon has been studied by microfocus Raman, micro X-ray diffraction (μXRD), electron probe micro analysis (EPMA) and synchrotron radiation microfocus X-ray absorption spectroscopy (XAS) to gain structural and chemical information on Ni. The data obtained has revealed that Ni is preferably accumulated in quantities up to 21 wt.% in lithiophoriteasbolane intermediates. The local environment of Ni shows NiMn distances ∼3.5 Å suggesting that Ni is sorbed mostly in inner-sphere complexes sitting on Mn vacancies and at the edge of the Mn layers. However it is shown that in the presence of Al the Ni is incorporated within the lithiophoriteasbolane intermediate by developing brucite-like interlayers. The understanding of Ni sorption mechanisms within the limonite horizon suggests that combined physicochemical factors such as soil porosity and pH regime have important implications for Ni mobility across the profile.
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Jun 2010
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I18-Microfocus Spectroscopy
Detectors
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Abstract: The long-wavelength MX beamline I23 currently under design at Diamond Light Source will be optimized in the X-ray energy range between 3 and 5 keV. At the moment no commercial off-the-shelf detector with high quantum efficiency and dynamic range is available to cover the large area required for diffraction experiments in this energy range. The hybrid pixel detector technology used in PILATUS detectors could overcome these limitations as the modular design could allow a large coverage in reciprocal space and high detection efficiency. Experiments were carried out on the Microfocus Spectroscopy beamline I18 at Diamond Light Source to test the performance of a 100K PILATUS module in the low-energy range from 2.3 to 3.7 keV.
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Jun 2010
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I18-Microfocus Spectroscopy
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Mary
Finnegan
,
Joanna
Collingwood
,
Jon
Dobson
,
Vijay
Antharam
,
Albina
Mikhailova
,
Mark
Davidson
,
JP
Bullivant
,
John
Forder
,
Chris
Batich
,
Naomi
Visanji
,
Fred
Mosselmans
,
Paul
Quinn
Diamond Proposal Number(s):
[4911]
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Jun 2010
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I18-Microfocus Spectroscopy
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Abstract: Implant-derived material from metal-on-metal (MOM) hip arthroplasties may be responsible for an unexplained tissue inflammatory response. The chemical form of the metal species in the tissues is predominantly chromium (Cr), but the currently used techniques have not been able to determine whether this is Cr(III) phosphate or Cr(III) oxide. The analytical challenge must overcome the fact that the metal in the tissues is at a relatively low concentration and tissue preparation or the microscopy beam used can affect the results. Microfocus X-ray spectroscopy using a synchrotron beam is useful in addressing both these issues. Using this technique we compared tissue from failed MOM hips with: (1) tissue from metal-on-polyethylene (MOP) hips; (2) chemical standards; (3) metal discs cut from MOM hips. The most abundant implant-related species in all MOM hip tissues contained Cr. Comparison with standards revealed the chemical form was Cr(III) phosphate, which did not vary with manufacturer type (four types analysed) or level of blood metal ions. Cobalt (Co) and molybdenum (Mo) were occasionally present in areas of high Cr. Co was normally found in a metallic state in the tissue, while Mo was found in an oxidized state. The variety of metallic species may have arisen from corrosion, wear or a combination of both. No evidence of Cr(VI) was seen in the tissues examined.
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Jun 2010
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I18-Microfocus Spectroscopy
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Paul
Schofield
,
Andrew
Smith
,
Fred
Mosselmans
,
Hendrik
Ohldag
,
Andreas
Scholl
,
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: A factory in Colonie (NY, USA) emitted c. 4.8 ± 1 tonnes of depleted uranium (DU) particulates into a suburban environment during 1958 – 1984. These particulates were initially dispersed by prevailing winds. Quadrupole inductively coupled plasma mass spectrometry (ICP-MS), laser ablation multicollector (LA-MC-) ICP-MS, scanning electron microscopy (SEM) and microfocus extended X-ray absorption fine structure (?EXAFS) spectroscopy have been used to characterise soils, dusts, vegetation, and individual particles. The concentration range of natural uranium in Colonie soils is 0.7 — 2.1 ?g g-1; with total uranium up to 500 ± 40 ?g g-1 in DU contaminated soils. Bioturbation can account for dispersal of contaminant from the soil surface. Primary morphologies are described for uraniferous particles from soils and dusts. Polycrystalline, often hollow microscopic uranium oxide spheres are similar to particles produced by DU munitions impacting armoured targets. These survive as UO2+x and U3O8, the least bioaccessible oxides of uranium. Fruit and wood samples were contaminated by DU, demonstrating limited bioavailability. Deviation of 235U/238U from the natural isotope ratio allows detection of DU in soils to at least 5.6 km from site. The average DU ‘end-member’ composition aggregated in soil samples comprises (2.05 ± 0.06) x10-3 235U/238U, (3.2 ± 0.1) x10-5 236U/238U, and (7.1 ± 0.3) x10-6 234U/238U. Individual uranium oxide grains were analysed by LA-MC-ICP-MS, all of which were from DU, with variable isotopic compositions (236U/238U, 235U/238U & 234U/238U). There is no evidence of enriched uranium in Colonie soils and dusts. The isotopic compositions of the Colonie particles can be explained by the inhomogeneous mixing of at least seven batches of tails from the Paducah gaseous diffusion plant, which are identified as the origins of the DU feedstocks used by National Lead Industries at Colonie. LA-MC-ICP-MS is recommended for nuclear forensic applications. This case-study is an attractive analogue for battlefield contamination.
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Mar 2010
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I18-Microfocus Spectroscopy
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Feb 2010
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I18-Microfocus Spectroscopy
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Abstract: We have used synchrotron Fe-XANES, XRS, microRaman, and SEM-TEM analyses of Stardust track 41 slice and track 121 terminal area slices to identify Fe oxide (magnetite-hematite and amorphous oxide), Fe-Ti oxide, and V-rich chromite (Fe-Cr-V-Ti-Mn oxide) grains ranging in size from 200 nm to ∼10 μm. They co-exist with relict FeNi metal. Both Fe-XANES and microRaman analyses suggest that the FeNi metal and magnetite (Fe2O3FeO) also contain some hematite (Fe2O3). The FeNi has been partially oxidized (probably during capture), but on the basis of our experimental work with a light-gas gun and microRaman analyses, we believe that some of the magnetite-hematite mixtures may have originated on Wild 2. The terminal samples from track 121 also contain traces of sulfide and Mg-rich silicate minerals. Our results show an unequilibrated mixture of reduced and oxidized Fe-bearing minerals in the Wild 2 samples in an analogous way to mineral assemblages seen in carbonaceous chondrites and interplanetary dust particles. The samples contain some evidence for terrestrial contamination, for example, occasional Zn-bearing grains and amorphous Fe oxide in track 121 for which evidence of a cometary origin is lacking.
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Feb 2010
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I18-Microfocus Spectroscopy
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Abstract: We present Ba L3-X-ray Absorption Fine Structure (XAFS) data from a suite of barium carbonates (witherite, alstonite, barytocalcite), hydroxides, sulfate(vi) (barite) and a Ba-bearing organic compound to explore whether Ba L3-XAFS could be used to fingerprint structural states in biominerals such as celestite, aragonite and calcite. Although there is a general similarity between all X-ray Absorption Near Edge Structure (XANES), subtle differences are observed in detail, which allow almost all phases to be distinguished. The XANES are considered as composites of four components, termed ‘A’ (5255 eV), ‘B’ (5258 eV), ‘C’ (5268 eV) and ‘D’ (5273 eV). ‘A’ is observed in barium hydroxides and most visible in the first derivatives of the XANES data. The minimum after the Ba L3 white line lies at 5257 eV for most materials but higher (5261 eV) for barium hydroxides due to the influence of the ‘A’ component. ‘B’ is present in aragonite-group minerals (witherite and alstonite) and may be a fingerprint of that structural state. ‘C’ and ‘D’ overlap and form a board hump at ∼ 5270 eV, but the relative proportions of ‘C’ and ‘D’ are variable between phases and are to some degree diagnostic. Refinement of Extended X-ray Absorption Fine Structure (EXAFS) allows estimates of first shell (Ba–O) bond distances in all materials, which are within 4% of average distances estimated from diffraction studies. Subsequent shells (Ba–S for barite; Ba–metal in witherite, alstonite and barytocalcite) can be resolved. The state of Ba:Ca order in alstonite and barytocalcite is successfully modelled and both are found to be fully ordered. The significant static disorder in Ba-bearing minerals is accommodated successfully by large Debye–Waller values in the refinements. Combinations of XANES and EXAFS allow all phases to be identified, with the exception that the two hydrated barium hydroxides cannot be distinguished from each other. The XANES of a celestite (SrSO4 containing ∼ 100 ppm Ba) is comparable to the barite spectra after only seven cycles (collected over < 5 h), showing that XANES can be resolved in samples with low Ba concentrations. However we were unable to analyse successfully an aragonitic Porites coral skeleton (containing ∼ 3–4 ppm Ba) using the current instrumentation due to the proximity in energy of Ca Kα secondary X-radiation to the Ba Lα energy and which overloaded the X-ray detector. The use of multilayer crystal detectors will be required to resolve the Ba Lα energy in calcium carbonate samples containing low Ba concentrations. Alternatively Ba EXAFS may be accessible through the Ba K edge.
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Jan 2010
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I18-Microfocus Spectroscopy
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J. Frederick W.
Mosselmans
,
Paul
Quinn
,
Andy
Dent
,
Stuart
Cavill
,
Sofia
Diaz-moreno
,
Andy
Peach
,
Pete
Leicester
,
Stephen
Keylock
,
Simon
Gregory
,
Kirk
Atkinson
,
Josep
Roque Rosell
Abstract: The design and performance of the microfocus spectroscopy beamline at the Diamond Light Source are described. The beamline is based on a 27 mm-period undulator to give an operable energy range between 2 and 20.7 keV, enabling it to cover the K-edges of the elements from P to Mo and the L(3)-edges from Sr to Pu. Micro-X-ray fluorescence, micro-EXAFS and micro-X-ray diffraction have all been achieved on the beamline with a spot size of similar to 3 mu m. The principal optical elements of the beamline consist of a toroid mirror, a liquid-nitrogen-cooled double-crystal monochromator and a pair of bimorph Kirkpatrick-Baez mirrors. The performance of the optics is compared with theoretical values and a few of the early experimental results are summarized.
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Nov 2009
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