Conference Publications

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Browsing Conference Publications by Subject "Absorption spectroscopy"

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    Ferric iron geometry and coordination during hydrolysis and ferrihydrite precipitation
    (Mineralogical Society of Great Britain & Ireland, 2011-10-01) Collins, RN; Rose, AL; Glover, CJ; Boland, DD; Payne, TE; Waite, TD
    Definitive structural characterisation of ferrihydrite has challenged scientists primarily due to its nanosized particles and inherent long-range structural disorder which challenges analytical methodology (and modelling) typically employed to determine the structure of minerals. Here we report on the application of a synchrotron quick-scanning X-ray absorption spectroscopy (XAS) approach, which allows the collection of Extended X-ray Absorption Fine Structure (EXAFS) spectral data to k = 15 Å-1 in < 1 minute, to obtain unparalleled iron Kedge data on the hydrolysis of FeIII(H2O)6 and ferrihydrite precipitation. Modelling of the pre-edge and EXAFS data: 1) supports theoretical studies which have suggested the existence of a monomeric penta-coordinated FeIII hydrolysis species and; 2) corroborates recently proposed structural models of ferrihydrite that contain tetrahedral FeIII. Modelling results indicate that ferrihydrite consists of 15 to 25 % tetrahedral FeIII and suggest that this geometry must be included in any comprehensive structural model of ferrihydrite and, furthermore, should be considered when evaluating the reactivity, stability and other structure-property relationships of this mineral. © 2011 The Authors.
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    Status of the x-ray absorption spectroscopy (XAS) beamline at the Australian synchrotron
    (American Institute of Physics, 2007-02-02) Glover, CJ; McKinlay, J; Clift, M; Barg, B; Boldeman, JW; Ridgway, MC; Foran, GJ; Garrett, RL; Lay, PA; Broadbent, A
    We present herein the current status of the X-ray Absorption Spectroscopy (XAS) Beamline at the 3 GeV Australian Synchrotron. The optical design and performance, details of the insertion device (Wiggler), end station capabilities and construction and commissioning timeline are given.
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    Synroc derivatives for the Hanford waste remediation task
    (Materials Research Society, 1997) Vance, ER; Hart, KP; Day, RA; Carter, ML; Hambley, M; Blackford, MG; Begg, BD
    Three wt% each of Cs and Tc were mixed with the standard Synroc precursor and the ceramic was formed by hot-pressing. Attempts were made to incorporate the Tc as either metal or Tc 4+, using different redox conditions in processing. Volatile losses of Tc during calcination were < 0.1% in all cases. Short-term Tc leach rates when the Tc was present as a metal alloy were in the order of 10−4 g/m /d at 90°C with frequently changed water, and decreased with increasing leaching time. The valence of the Tc was monitored by X-ray absorption spectroscopy at the drying and calcination stages of the production. The general viability of Synroc/glass composites for immobilising the Hanford HLW sludges is further demonstrated by using further refinements of additive schemes for the inactive “All-blend” formulation and initial studies using the U-containing “All-blend” waste formulation. © Materials Research Society 1997