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  • 1
    facet.materialart.
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    Analysis of biogenic magnetite nanoparticles (2013)
    PANGAEA
    In:  Supplement to: Byrne, James M; Coker, V S; Moise, S; Wincott, P L; Vaughan, D J; Tuna, F; Arenholz, E; van der Laan, G; Pattrick, R A D P; Lloyd, J R; Telling, N D (2013): Controlled cobalt doping in biogenic magnetite nanoparticles. Journal of The Royal Society Interface, 10(83), 20130134-20130134, https://doi.org/10.1098/rsif.2013.0134
    Details
    Publication Date: 2023-01-13
    Description: Cobalt doped magnetite (CoxFe3-xO4) nanoparticles have been produced through the microbial reduction of cobalt-iron oxyhydroxide by the bacterium Geobacter sulfurreducens. The materials produced, as measured by SQUID, x-ray magnetic circular dichroism, Mössbauer spectroscopy, etc., show dramatic increases in coercivity with increasing cobalt content without a major decrease in overall saturation magnetization. Structural and magnetization analyses reveal a reduction in particle size to 〈4 nm at the highest Co content, combined with an increase in the effective anisotropy of the magnetic nanoparticles. The potential use of these biogenic nanoparticles in aqueous suspensions for magnetic hyperthermia applications is demonstrated. Further analysis of the distribution of cations within the ferrite spinel indicates that the cobalt is predominantly incorporated in octahedral coordination, achieved by the substitution of Fe2+ site with Co2+, with up to 17 per cent Co substituted into tetrahedral sites.
    Type: Dataset
    Format: application/zip, 695.2 kBytes
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    DATA PANGAEA
  • 2
    Electronic Resource
    Electronic Resource
    Sulphur isotopic investigation of lower carboniferous vein deposits of the British Isles (1989)
    Springer
    Mineralium deposita 24 (1989), S. 148-153 
    Details
    ISSN: 1432-1866
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Similar characteristics and age data suggest that the Pb + Zn vein deposits hosted by Lower Palaeozoic and Vendian strata of the British Isles form a genetically related group, coeval with the Lower Carboniferous carbonatehosted base-metal deposits of Ireland. Sulphur isotopic data demonstrate that there were separate sulphide and sulphate sulphur sources for the vein minerals. δ34S values from minerals in individual vein systems are consistent but there is a large variation between deposits, revealing distinctive local sulphur sources. The data suggests that sulphide sulphur (total range of values of δ34SH2S of -6.5 to 18.62‰) was derived from the underlying strata while the sulphate (baryte) sulphur source (δ34Sbaryte mainly in the range 12 to 24‰) was groundwater or surface water that mixed with rising hydrothermal fluids in the upper reaches of the veins.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00206319
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  • 3
    Electronic Resource
    Electronic Resource
    Sulphur isotopic investigation of vein lead-zinc mineralization at Tyndrum, Scotland (1983)
    Springer
    Mineralium deposita 18 (1983), S. 477-485 
    Details
    ISSN: 1432-1866
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The Tyndrum Pb+Zn veins, hosted by late Proterozoic quartzites, were probably generated in the Tournaisian (360 Ma). By determination of sulphur isotopic ratios of vein minerals three aspects of the Tyndrum mineralization were addressed, (i) sulphate sulphur sources; (ii) reduced sulphur source; (iii) isotopic equilibrium in the vein system including geothermometry. Twelve galenas have δ34S values ranging from +3.55 ‰ to +6.38 ‰ (this excludes one value of +11.21 ‰ from a large but nearly barren quartz vein). Other sulphides are enriched or depleted in 34S in the sense expected for isotopic equilibrium although there is no evidence for isotopic equilibrium between the vein minerals. The sulphide sulphur source was probably in the Dalradian metasediments where disseminated pyrite averages +6 ‰. Baryte had δ34S values averaging 14 ‰ and was therefore not in isotopic equilibrium with sulphides: a continental groundwater source is most likely.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00204492
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  • 4
    Electronic Resource
    Electronic Resource
    Floating sulfides: activating and poisoning surfaces (1999)
    Chester : International Union of Crystallography (IUCr)
    Journal of synchrotron radiation 6 (1999), S. 664-666 
    Details
    ISSN: 1600-5775
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0909049599002009
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  • 5
    Electronic Resource
    Electronic Resource
    Gold-Silver vein mineralization at Tyndrum, Scotland (1988)
    Springer
    Mineralogy and petrology 38 (1988), S. 61-76 
    Details
    ISSN: 1438-1168
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Zusammenfassung In der Gang-Vererzung von Tyndrum, Schottland, kommen eine Gold-Silber-Legierung, Hessit, Petzit und Sylvanit vor. Außerdem ergaben Mikrosondenanalysen das Vorhandensein von zwei unbekannten Ag-Te-S Phasen. Die Untersuchungen von Flüssigkeitseinschlüssen zeigen, daß die für die frühe Mineralisation verantwortlichen Lösungen ∼ 7.0% Mol.% CO2 und 7 Gew.% NaCl enthalten haben. Die Homogenisie-rungstemperaturen liegen im Bereich von 295-325°C und weisen auf eine Tiefe der Gangentstehung von ∼ 4 km hin. Die Au-Ag-Te Mineralbildung kam vermutlich durch Abkühlung und Adsorption von Gold auf Pyrit zustande. Δ34S-Werte von + 1.8%0, gemessen an Bleiglanz aus Au-Ag-Te-Gängen deuten eine magmatische Schwefelherkunft an, während die Pb-Zn-Gangmineralisation eine andere Schwefelquelle vermuten läßt. Die Altersdatierung der Gänge von ∼ 380 Mio. Jahren läßt sich derzeit noch nicht sinnvoll interpretieren. Es wird angenommen, daß die Au-Ag-Vererzung von Tyndrum durch hydrothermale Aktivität im Zusammenhang mit einer an spätkaledonische Granite gebundenen Cu-Mo-Vererzung entstanden ist.
    Notes: Summary Electrum, hessite, petzite and sylvanite have been recorded from veins at Tyndrum, Scotland. Electron probe micro-analyses have also revealed two un-named Ag-Te-S phases. Fluid inclusion studies suggest that the mineralising fluids responsible for the precious metal mineralization contained ∼ 7.0 mol % CO2 and 7 wt % NaCl. TH (temperature of homogenisation) determinations were in the range 295°C to 325°C and a depth of vein formation ∼ 4 km is indicated. Mineral precipitation was probably caused by cooling and adsorption of gold onto pyrite. Δ34S values of + 1.8%o for galena from the Au + Ag + Te veins suggest a different (possibly igneous) sulphur source to that producing the Pb +Zn vein mineralization in the Tyndrum area. Although an age of ∼ 380 Ma was obtained using K-feldspar in the veins the data are not conclusive. It is argued that the Au + Ag mineralization at Tyndrum is due to hydrothermal activity related to Cu +Mo mineralization associated with the Late Caledonian granites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01162482
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  • 6
    Electronic Resource
    Electronic Resource
    3d transition metal L-edge X-ray absorption studies of the dichalcogenides of Fe, Co and Ni (1996)
    Springer
    Physics and chemistry of minerals 23 (1996), S. 403-408 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract The X-ray absorption spectra of the transition metal L3,2-edges of the dichalcogenides FeS2 (pyrite), FeSe2, FeTe2, CoS2, CoSe2, CoTe2, NiS2, NiSe2 and NiTe2 have been studied. These spectra are compared with theoretical simulations make using the atomic multiplet approach assuming on octahedral site for the metal atoms. The Ni spectra can be closely simulated using this approach but the Fe and Co spectra show less good fits to the experimental data. The reasons for this and its implications for the use of L-edge spectra in the study of such minerals are discussed in terms of the covalency and the ground states of the compounds; these results indicate the mixing of the ground states increases in the order Ni〈Co〈Fe.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00202026
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  • 7
    Electronic Resource
    Electronic Resource
    Oxidation state and electronic configuration determination of copper in tetrahedrite group minerals by L-edge X-ray absorption spectroscopy (1993)
    Springer
    Physics and chemistry of minerals 20 (1993), S. 395-401 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract L-edge X-ray absorption spectroscopy employing a synchrotron radiation source has been used to study the electronic structure and valency of Cu in the chemically and structurally complex tetrahedrite group of minerals. Mechanical mixtures of Cu2+O and Cu+FeS2 were used to estimate the relative cross sections of Cu2+ and Cu+; the absorption of Cu2+ at 931 eV is 25 times greater than that of Cu+ at 945 eV. Using this calibration, Cu2+/Cu ratios were found to vary from 0.00 to 0.054 in the tetrahedrite samples studied; the highest proportion of Cu2+ occurs in synthetic tetrahedrites with a composition close to Cu12Sb4S13. This study reveals the utility of the technique for determining the valence state of copper in complex minerals, allowing the crystal chemistry to be more fully characterised.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00203108
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  • 8
    Electronic Resource
    Electronic Resource
    X-ray absorption near-edge spectra of transition metal disulfides FeS2 (pyrite and marcasite), CoS2, NiS2 and CuS2, and their isomorphs FeAsS and CoAsS (1995)
    Springer
    Physics and chemistry of minerals 22 (1995), S. 311-317 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract Metal K- and L3-, sulfur K- and arsenic K- and L3-edge X-ray absorption near-edge spectra of a series of metal disulfides, FeS2 (both pyrite and marcasite), CoS2, NiS2, and CuS2, and their isomorphs, FeAsS and CoAsS, are presented. The features in this region of these spectra are interpreted using band structure and molecular orbital calculations in terms of the transitions from the 1s or 2p3/2 state to unoccupied states. The 3d transition metal L3-edge spectra of these materials show dependence on the degree of multiplet splitting in the final state, and thus offer less information on the electronic ground state. There are substantial differences in the spectra of the isostructural materials, whereas the spectra of the isotopes pyrite and marcasite show several similarities, illustrating the dependence of near-edge region on electronic structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00202771
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  • 9
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    Radiation damage in biotite mica by accelerated {alpha}-particles: A synchrotron microfocus X-ray diffraction and X-ray absorption spectroscopy studyk (2016)
    Mineralogical Society of America
    Details
    Publication Date: 2016-04-02
    Description: A critical radiation damage assessment of the materials that will be present in a Geological Disposal Facility (GDF) for radioactive waste is a priority for building a safety case. Detailed analysis of the effects of high-energy α-particle damage in phyllosilicates such as mica is a necessity, as these are model structures for both the clay-based backfill material and the highly sorbent components of a crystalline host rock. The α-radiation stability of biotite mica [general formula: K(Mg,Fe) 3 (Al,Si 3 O 10 )(F,OH) 2 ] has been investigated using the 5 MV tandem pelletron at the University of Manchester’s Dalton Cumbrian Facility (DCF) and both the microfocus spectroscopy (I18) and core X-ray absorption spectroscopy (B18) beamlines at Diamond Light Source (U.K.). Microfocus X-ray diffraction mapping has demonstrated extensive structural aberrations in the mica resulting from controlled exposure to the focused 4 He 2+ ion (α-particle) beam. Delivered doses were comparable to a-particle fluences expected in the highly active, near-field of a GDF. At doses up to 6.77 displacements per atom (dpa) in the region of highest particle fluence, biotite mica displays a heterogeneous structural response to irradiation on a micrometer scale, with sequential dilation and contraction of regions of the structure perpendicular to the sheets, as well as a general overall contraction of the phyllosilicate layer spacing. At the peak of ion fluence, the structure collapses under a high point defect density and amorphous areas are pervasive among altered domains of the original lattice. Such structural alterations are likely to affect the material’s capacity to sorb and retain escaped radionuclides over long timescales; increased edge site availability may favor increased sorption while interlayer uptake will likely be reduced due to collapse. Radiation-induced reduction of structural iron at the region of highest structural damage across an α-particle’s track has been demonstrated by Fe K -edge X-ray absorption near edge spectroscopy (XANES) and local structural disorder has been confirmed by analysis of both potassium K -edge XANES and Fe K -edge extended X-ray absorption fine structure analysis. An infrared absorption study of deformations in the OH – stretching region, along with electron probe microanalysis complements the synchrotron data presented here.
    Print ISSN: 0003-004X
    Electronic ISSN: 1945-3027
    Topics: Geosciences
    Published by Mineralogical Society of America
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  • 10
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    High-resolution imaging of biotite using focal series exit wavefunction restoration and the graphene mechanical exfoliation method (2015)
    Mineralogical Society of Great Britain and Ireland
    Details
    Publication Date: 2015-07-03
    Description: We have applied mechanical exfoliation for the preparation of ultra-thin samples of the phyllosilicate mineral biotite. We demonstrate that the ‘scotch tape’ approach, which was made famous as an early method for production of single-atom-thick graphene, can be used for production of sheet-silicate specimens that are sufficiently thin to allow high-resolution transmission electron microscope (HRTEM) imaging to be achieved successfully while also being free from the specimen preparation artefacts that are often caused by ion-beam milling techniques. Exfoliation of the biotite parallel to the (001) planes has produced layers as thin as two structural TOT units thick (~2 nm). The minimal specimen thickness enabled not only HRTEM imaging but also the application of subsequent exit wavefunction restoration to reveal the pristine biotite lattice. Exit wavefunction restoration recovers the full complex electron wave from a focal series of HRTEM images, removing the effects of coherent lens aberrations. This combination of methods therefore produces images in which the observed features are readily interpreted to obtain atomic resolution structural information.
    Print ISSN: 0026-461X
    Electronic ISSN: 1471-8022
    Topics: Geosciences
    Published by Mineralogical Society of Great Britain and Ireland
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