I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[9597]
Open Access
Abstract: The Fe–Mg exchange coefficient between olivine (ol) and melt (m), defined as KdFe𝑇−Mg
Kd
Fe
T
−
Mg
= (Feol/Fem)·(Mgm/Mgol), with all FeT expressed as Fe2+, is one of the most widely used parameters in petrology. We explore the effect of redox conditions on KdFe𝑇−Mg
Kd
Fe
T
−
Mg
using experimental, olivine-saturated basaltic glasses with variable H2O (≤ 7 wt%) over a wide range of fO2 (iron-wüstite buffer to air), pressure (≤ 1.7 GPa), temperature (1025–1425 °C) and melt composition. The ratio of Fe3+ to total Fe (Fe3+/∑Fe), as determined by Fe K-edge µXANES and/or Synchrotron Mössbauer Source (SMS) spectroscopy, lies in the range 0–0.84. Measured Fe3+/∑Fe is consistent (± 0.05) with published algorithms and appears insensitive to dissolved H2O. Combining our new data with published experimental data having measured glass Fe3+/∑Fe, we show that for Fo65–98 olivine in equilibrium with basaltic and basaltic andesite melts, KdFe𝑇−Mg
Kd
Fe
T
−
Mg
decreases linearly with Fe3+/∑Fe with a slope and intercept of 0.3135 ± 0.0011. After accounting for non-ideal mixing of forsterite and fayalite in olivine, using a symmetrical regular solution model, the slope and intercept become 0.3642 ± 0.0011. This is the value at Fo50 olivine; at higher and lower Fo the value will be reduced by an amount related to olivine non-ideality. Our approach provides a straightforward means to determine Fe3+/∑Fe in olivine-bearing experimental melts, from which fO2 can be calculated. In contrast to KdFe𝑇−Mg
Kd
Fe
T
−
Mg
, the Mn–Mg exchange coefficient, KdMn−Mg
Kd
Mn
−
Mg
, is relatively constant over a wide range of P–T–fO2 conditions. We present an expression for KdMn−Mg
Kd
Mn
−
Mg
that incorporates the effects of temperature and olivine composition using the lattice strain model. By applying our experimentally-calibrated expressions for KdFe𝑇−Mg
Kd
Fe
T
−
Mg
and KdMn−Mg
Kd
Mn
−
Mg
to olivine-hosted melt inclusions analysed by electron microprobe it is possible to correct simultaneously for post-entrapment crystallisation (or dissolution) and calculate melt Fe3+/∑Fe to a precision of ≤ 0.04.
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Oct 2020
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I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[21717]
Abstract: Corrosion research related to CO2-containing environments has focused over the past few decades on siderite formation (FeCO3) as a main corrosion product on carbon steel, yet the influence of Ca and other ions on its chemical and structural characteristics is not fully understood. Metal-localized corrosion is the biggest industrial challenge because of the unknown and unpredictable character of this phenomenon that frequently leads to failure. We report here the role of Ca and formation of iron-calcium carbonate (FexCayCO3) through a spiral growth model as in the calcite system and quantify the replacement of Fe2+ by Ca2+ ions in the structure of FeCO3 to form FexCayCO3. The incorporation of Ca2+ inhibits the completion of spiral segments on the growth of the rhombohedral crystals of FeCO3, promoting an enlargement of its structure along the c-axis. This leads to distortions in the chemical structure and morphology affecting the chemical and mechanical properties. Under flow conditions over time in an undersaturated environment, Ca is leached out from the expanded structure of FexCayCO3 increasing the solubility of the crystals, weakening the mechanical properties of the resulting corrosion films and stimulating localized corrosion.
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Oct 2020
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I18-Microfocus Spectroscopy
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Thomas
Christiansen
,
Marine
Cotte
,
Wout
De Nolf
,
Elouan
Mouro
,
Juan
Reyes-herrera
,
Steven
De Meyer
,
Frederik
Vanmeert
,
Nati
Salvado
,
Victor
Gonzalez
,
Poul Erik
Lindelof
,
Kell
Mortensen
,
Kim
Ryholt
,
Koen
Janssens
,
Sine
Larsen
Diamond Proposal Number(s):
[23348]
Open Access
Abstract: A hitherto unknown composition is highlighted in the red and black inks preserved on ancient Egyptian papyri from the Roman period (circa 100 to 200 CE). Synchrotron-based macro–X-ray fluorescence (XRF) mapping brings to light the presence of iron (Fe) and lead (Pb) compounds in the majority of the red inks inscribed on 12 papyrus fragments from the Tebtunis temple library. The iron-based compounds in the inks can be assigned to ocher, notably due to the colocalization of Fe with aluminum, and the detection of hematite (Fe2O3) by micro–X-ray diffraction. Using the same techniques together with micro-Fourier transform infrared spectroscopy, Pb is shown to be associated with fatty acid phosphate, sulfate, chloride, and carboxylate ions. Moreover, micro-XRF maps reveal a peculiar distribution and colocalization of Pb, phosphorus (P), and sulfur (S), which are present at the micrometric scale resembling diffused “coffee rings” surrounding the ocher particles imbedded in the red letters, and at the submicrometric scale concentrated in the papyrus cell walls. A similar Pb, P, and S composition was found in three black inks, suggesting that the same lead components were employed in the manufacture of carbon-based inks. Bearing in mind that pigments such as red lead (Pb3O4) and lead white (hydrocerussite [Pb3(CO3)2(OH)2] and/or cerussite [PbCO3]) were not detected, the results presented here suggest that the lead compound in the ink was used as a drier rather than as a pigment. Accordingly, the study calls for a reassessment of the composition of lead-based components in ancient Mediterranean pigments.
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Oct 2020
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I02-Macromolecular Crystallography
I13-1-Coherence
I13-2-Diamond Manchester Imaging
I18-Microfocus Spectroscopy
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Abstract: Background: Skogsbergia lerneri (Kornicker, 1958) is a species of ostracod which, like all crustaceans, has a protective exoskeleton (or carapace). As well as being used for a protective function, the S. lerneri carapace is also transparent. Understanding how the carapace is transparent while retaining its protective function was the primary aim of this thesis.
Results: Ultrastructural analysis showed that the carapace consisted of an epicuticle, exocuticle and an endocuticle split into a calcified, crystalline endocuticle and a laminated endocuticle. Numerous structural adaptations were seen to minimise refractive index changes at the layer intersections. These layers developed along with growth of the ostracod, maintaining similar proportions throughout. Microstructural analysis identified a chitin based second harmonic generated signal from the carapace. Pixel analysis of this signal showed a consistent level of chitin expression (~60-80% of the total carapace) throughout all the developmental stages except instar 4, which showed a lower level of expression. Elemental analysis showed that the calcified, crystalline layer comprised mainly calcium, oxygen and magnesium, leading to the assumption that the structures were calcium carbonate. X-ray absorption near edge structure analysis revealed that the calcium carbonate consisted of entirely amorphous calcium carbonate in the early to middle stages of development and a mix of amorphous and aragonite in the later stages. Unlike most crustaceans, calcite was not seen in any carapaces. Optical testing showed a consistent refractive index across all stages (1.401-1.406) leading to a mean 99.94% transmission of light at the carapace surface in seawater. Spectrophotometric results showed that light transmission increased at longer wavelengths in the younger samples but maintained a consistent level by the adult stage.
Conclusions: Through the various structural adaptations of the carapace, in combination with the rare calcium carbonate polymorph distribution and its overall thinness, the S. lerneri is able to maintain its transparency without sacrificing many of its physical properties.
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Sep 2020
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I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[22876]
Abstract: Fly ash represents a promising alternative source of rare earth elements (REE). However, information on REE containing mineral phases and their association with other fly ash components, vital for REE recovery from fly ash, is currently lacking. Herein, the mass fraction, distribution, crystallography and solid-state chemistry of REE, U and Th in Nigerian simulated fly ash samples were characterised using a range of laboratory and synchrotron x-ray based analytical techniques to underpin future extraction methodologies. Inductively coupled plasma mass spectrometry following full-acid digest of forty-five samples revealed recoverable average total REE content which ranged between 442 mgkg−1and 625 mgkg−1, comprising over 30 wt% of the critical REE Nd, Eu, Tb, Dy, Y and Er. These REE within the fly ash samples were found to be most frequently associated with discrete monazite, xenotime and Y-bearing zircon mineral particles, with the former the most detected, which could be beneficiated through gravity separation. Analysis of monazite particles isolated from the composite samples through a complimentary suite of analytical synchrotron radiation techniques revealed a core-shell pattern, with the shell rich in colocalised Ce, Nd and La, and the core enrich in both U and Th. Ce in monazite was found to exist in a mixed trivalent and tetravalent oxidation state, with the monazite structure amorphized due to the high temperature combustion process. Such results demonstrate the strong co-association and physical distribution of REE, U and Th within monazite in fly ash; knowledge of which can subsequently be used to optimise or develop a more selective, cost-effective and environmentally friendly solvent extraction methodology, by targeting the strongly colocalised and surface bound REE in fly ash monazite particles.
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Aug 2020
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I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[7254]
Open Access
Abstract: In this work, the effects of the protozoan Neospora caninum on the bioenergetics, chemical composition, and elemental content of human brain microvascular endothelial cells (hBMECs) were investigated. We showed that N. caninum can impair cell mitochondrial (Mt) function and causes an arrest in host cell cycling at S and G2 phases. These adverse effects were also associated with altered expression of genes involved in Mt energy metabolism, suggesting Mt dysfunction caused by N. caninum infection. Fourier Transform Infrared (FTIR) spectroscopy analysis of hBMECs revealed alterations in the FTIR bands as a function of infection, where infected cells showed alterations in the absorption bands of lipid (2924 cm−1), amide I protein (1649 cm−1), amide II protein (1537 cm−1), nucleic acids and carbohydrates (1092 cm−1, 1047 cm−1, and 939 cm−1). By using quantitative synchrotron radiation X-ray fluorescence (μSR-XRF) imaging and quantification of the trace elements Zn, Cu and Fe, we detected an increase in the levels of Zn and Cu from 3 to 24 h post infection (hpi) in infected cells compared to control cells, but there were no changes in the level of Fe. We also used Affymetrix array technology to investigate the global alteration in gene expression of hBMECs and rat brain microvascular endothelial cells (rBMVECs) in response to N. caninum infection at 24 hpi. The result of transcriptome profiling identified differentially expressed genes involved mainly in immune response, lipid metabolism and apoptosis. These data further our understanding of the molecular events that shape the interaction between N. caninum and blood-brain-barrier endothelial cells.
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Aug 2020
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I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[18676]
Abstract: The in-situ formation of lead-sulfur inorganic compounds in historical oil paintings can have a strong detrimental effect on an artwork’s physical and visual integrity. In this paper, paint micro-samples collected from several paintings from the Rijksmuseum (Amsterdam) and Mauritshuis (The Hague) collections were probed at the micro-scale using a combination of synchrotron micro-XRD and XRD-CT. This permitted to precisely identify the chemical nature of the in-situ formed crystalline compounds as well as to chart their distribution within paint layers at the microscopic level. This provided new information on the origin of the ions involved in the crystallization of the various newly formed mineral lead-sulfur products. The formation of palmierite K2Pb(SO4)2, anglesite PbSO4 and lanarkite Pb2(SO4)O in historical samples can thus be connected to paint stratigraphic build-up, environmental conditions and potential past restoration treatments.
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Jul 2020
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I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[23210]
Abstract: Mankind is facing a phosphorus (P) crisis. P recycling from anthropogenic waste is critical to close the P loop. Pyrolysis could be the ideal treatment for materials, such as sewage sludge, producing a safe, nutrient-rich biochar product while sequestering the inherent carbon (C). However, pyrolysed sewage sludge typically contains low levels of potassium (K) and plant available P making the material rather unsuitable for use as fertiliser. Here, a novel treatment was investigated to produce an optimised P and K biochar fertiliser. We doped sewage sludge with a low-cost mineral (2 and 5% potassium acetate) and pyrolysed it at 700°C. The percentage water-extractable of the total P content in biochar increased by 237-times with 5% K addition compared to the undoped biochar. After six water-extractions, all the K and 16% of P was obtained. Further optimisation is feasible through adjustments of the biochar pH or doping the feedstock with other forms of K. Using XANES and synchrotron XRF mapping, we identified highly soluble potassium hydrogen phosphate up to 200-300 µm below the biochar surface. This simple and cost-effective modification enables the use of sewage sludge as safe biochar fertiliser with tailored P availability that also supplies K, improves soil properties and sequesters C.
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Jul 2020
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I18-Microfocus Spectroscopy
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Abstract: Sulfur is a key volatile element in magmatic systems that exists in many phases (e.g. melt or gas), in multiple-oxidation states (S²⁻, S⁴⁺ and S⁶⁺), and has more than one stable isotope (e.g. ³²S and ³⁴S). Therefore, by measuring S, information regarding the conditions of a magma can be acquired. The aim of this work is to investigate what S can tell us about the behaviour of late-stage lunar basaltic magmas. An analytical protocol was developed to simultaneously measure S and Cl abundances and isotopes of lunar apatite in eleven lunar basalts with nano-scale secondary ion mass spectrometry (NanoSIMS). Additionally, a method was developed to measure the oxidation state of S in apatites of five mare basalts with X-ray absorption near-edge structure (XANES) spectroscopy at the S K-edge, making it possible to compare S oxidation state and S isotopes of lunar apatite for the first time.
Lunar apatites contain ~20–2,800 ppm S, with δ³⁴S values between -33.3 ± 3.8‰ and +36.4 ± 3.2‰ (2σ). The Cl abundance is ~350–7,230 ppm, with δ³⁷Cl values of +6.5‰ ± 0.9‰ to +36.5‰ ± 1.1‰ (2σ). All of the apatites have S⁶⁺/ΣS(tot) ratios of >0, with average S⁶⁺/ΣS(tot) values between 0.05 and 0.55.
An absence of correlation between S and Cl isotopes suggests a lack of evolutionary relationship between S and KREEP-rich components. The direction of S isotope fractionation, negative or positive, can be explained by degassing of H₂S and SO₂ from a relatively reduced (S²⁻) or oxidized (SO₄²⁻) late-stage silicate melt, respectively. The historical existence of relatively oxidized late-stage silicate melts is also evidenced by the presence of S⁶⁺ in lunar apatite. A positive trend is apparent between S⁶⁺/ΣS(tot) and δ³⁴S which is indicative of the dependence of S isotope fractionation on the oxygen fugacity of the late-stage silicate melt.
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Jul 2020
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I18-Microfocus Spectroscopy
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Antonios
Vamvakeros
,
Dorota
Matras
,
Simon D. M.
Jacques
,
Marco
Di Michiel
,
Stephen W. T.
Price
,
Pierre
Senecal
,
Miren
Agote Aran
,
Vesna
Middelkoop
,
Gavin B. G.
Stenning
,
J. Frederick W.
Mosselmans
,
Ilyas Z.
Ismagilov
,
Andrew M.
Beale
Diamond Proposal Number(s):
[14525]
Abstract: In this work, we present the results from multi-length-scale studies of a Mn-Na-W/SiO2 and a La-promoted Mn-Na-W/SiO2 catalyst during the oxidative coupling of methane reaction. The catalysts were investigated from the reactor level (mm scale) down to the single catalyst particle level (μm scale) with different synchrotron X-ray chemical computed tomography techniques (multi-modal chemical CT experiments). These operando spatially-resolved studies performed with XRD-CT (catalytic reactor) and multi-modal μ-XRF/XRD/absorption CT (single catalyst particle) revealed the multiple roles of the La promoter and how it provides the enhancement in catalyst performance. It is also shown that non-crystalline Mn species are part of the active catalyst component rather than crystalline Mn2O3/Mn7SiO12 or MnWO4.
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Jun 2020
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