Browsing by Author "Thorogood, GJ"
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- ItemAlternative Synroc formulations(Cambridge University Press/Springer Nature, 2011-02-25) Vance, ER; Smith, KL; Thorogood, GJ; Begg, BD; Moricca, SA; Angel, PJ; Stewart, MWA; Ball, CJPerovskite is the least durable of the resistate minerals comprising Synroc-C and it is desirable to reduce its abundance in Synroc. Kinetic limitations and competition with Csapparently affect the incorporation of Sr into hollandite during hot-pressing at 1200°C/20 MPa so that ~ 10% of perovskite (a value below the percolation limit) is probably an optimum target. Zirconolite-rich Synroc formulations have been prepared for actinide-rich wastes. Background XRD and TEM studies have also been performed to study the crystal-chemical behaviour of Nd (a simulant of trivalent actinides) in zirconolite. Either rare-earth compensated perovskite or freudenbergite in Synroc can evidently be used to immobilise Na-bearing HLW. © 1992 Materials Research Society
- ItemAnomalous lattice parameter increase in alkali earth aluminium substituted tungsten defect pyrochlores(Elsevier, 2009-03) Thorogood, GJ; Kennedy, BJ; Peterson, VK; Elcombe, MM; Kearley, GJ; Hanna, JV; Luca, VThe structures of the defect pyrochlores AAl(0.33)W(1.67)O(6) where A = K, Rb or Cs have been investigated using X-ray and neutron powder diffraction methods as well as the ab initio modelling program VASP The three cubic pyrochlores exhibit a non-linear increase in lattice parameter with respect to ionic radius of the A cation as a consequence of displacive disorder of the A-type cations. Solid state Al-27 MAS NMR studies of this pyrochlore system reveal shifts in the delta-21-22 ppm range that are indicative of pseudo-5 coordinate Al environments and emanate frorn distorted Al octahedral with one abnormally long Al. O bond. Solid state K-39, Rb-85, Rb-87 and Cs-133 MAS and static NMR Studies reflect the local cation disorder demonstrated in the structural Studies. © 2008, Elsevier Ltd.
- ItemAntiferromagnetism in a technetium oxide. Structure of CaTcO3(American Chemical Society, 2011-01-16) Avdeev, M; Thorogood, GJ; Carter, ML; Kennedy, BJ; Ting, J; Singh, DJ; Wallwork, KSThe technetium perovskite CaTcO3 has been synthesized. Combining synchrotron X-ray and neutron diffraction, we found that CaTcO3 is an antiferromagnetic with a surprisingly high Neel temperature of ~800 K. The transition to the magnetic state does not involve a structural change, but there is obvious magnetostriction. Electronic structure calculations confirm the experimental results. © 2011, American Chemical Society
- ItemAppendix 2: Metal crystallography(CSIRO Publishing, 2014-10-01) Thorogood, GJThe micrograph in Fig. App 2.1, from the back plate, is a typical example of grain deformation due to the metal being worked below its recrystallization temperature (see also Figs App 2.2, App 2.3). An acetate replica taken edge-on from the breast plate (see photo), however, showed a banded structure. This is due to the original rolling of the metal and indicates that the bulk of the metal has not been heated above the recrystallization temperature. © 2014 CSIRO Publishing.
- ItemAuCuAl shape memory alloys for use in nano-actuators(Australian Institute of Physics, 2010-02-02) Bhatia, VK; Kealley, CS; Thorogood, GJ; Dowd, A; Cortie, MBAlthough Al, Au and Cu each has the face centered cubic structure in elemental solid form, they do not readily alloy with one another, and instead form a series of binary and ternary intermetallic compounds. The ternary system is very interesting and contains, amongst other features, an 18-carat shape memory electron compound sometimes called ‘Spangold’  ( Figure 1). Shape memory alloys are remarkable in that they have the ability to return to their initial state and shape after being deformed. This ability arises from a martensitic (displacive) phase transformation (see Figure 2), which is strongly influenced by temperature, crystal structure and degree of ordering. It is already known that the parent phase of ‘Spangold’ must contain at least a minimum degree of ternary ordering before the reversible displacive transformation needed for the shape memory effect can take place . Furthermore, the parent phase has been found to have the L21 ordered body-centered cubic packing arrangement , while it has been reported that the martensite can be described using a monoclinic unit cell . Here we examine the possibility of using this compound as a nano-actuator. Magnetron sputtering was used to deposit the Au, Cu and Al. The films were then characterized using x-ray reflectometry (see figure 3), grazing incidence X-ray diffraction, scanning electron microscopy and atomic force microscopy. The properties of these films are compared with that of bulk samples.
- ItemA carved ivory cylinder from Akchakhan-kala, Uzbekistan: problems of dating and provenance(Elsevier B.V., 2016-02-01) Betts, AVG; Dodson, JR; Garbe, U; Bertuch, F; Thorogood, GJExcavations at Akchakhan-kala in Uzbekistan, a region known in antiquity as Chorasmia, recovered a large, elaborately carved and heavily burned cylinder of some very solid material. Its poor condition made identification of the raw material difficult. Here we used neutron tomography to examine the internal structure in a non-destructive way, and X-ray Diffraction to determine the main chemical composition of the material which confirmed it as ivory. This was followed by preparation for stable isotope and radiocarbon analysis. The stable isotope analysis suggests a tropical or subtropical grassland source for the ivory, which is unlikely to be from Uzbekistan. The dating shows the ivory to be much earlier than the context in which it was found. Whatever its origin, the ivory travelled far to reach Chorasmia, perhaps in its raw state, and perhaps also for some time in its carved form. © 2015 Elsevier Ltd.
- ItemCation antisite disorder in uranium-doped gadolinium zirconate pyrochlores(Elsevier, 2014-09-01) Gregg, DJ; Zhang, ZM; Thorogood, GJ; Kennedy, BJ; Kimpton, JA; Griffiths, GJ; Guagliardo, PR; Lumpkin, GR; Vance, ERThe incorporation of uranium into gadolinium zirconate (Gd2Zr2O7) is investigated by synchrotron X-ray powder diffraction and X-ray absorption near-edge structure (XANES) spectroscopy. The results suggest that the uranium cation is largely located on the pyrochlore B-site instead of the targeted A-site. Cation disorder in Gd2Zr2O7 and U-doped Gd2Zr2O7 is investigated by positron annihilation lifetime spectroscopy (PALS) which demonstrates the absence of cation vacancies in these systems. This work provides direct evidence for cation antisite (A- and B-site mixing) disorder in U-doped and off-stoichiometric Gd2Zr2O7 pyrochlore. © 2014, Elsevier B.V.
- ItemCation disorder in NaW2O6+δ·nH2−zO post-ion exchange with K, Rb, Sr, and Cs(Pergamon-Elsevier Science Ltd, 2011-06-01) Thorogood, GJ; Kennedy, BJ; Avdeev, M; Peterson, VK; Hanna, JV; Luca, VThe structure of the defect pyrochlore NaW2O6+delta center dot nH(2-z)O after ion exchange with K, Rb, Sr or Cs for Na has been investigated using thermal analysis, solid-state nuclear magnetic resonance, laboratory X-ray and neutron diffraction methods. Neutron diffraction studies show that both the A-type cations (Na+, K+, Rb+, and/or Cs+) and the water molecules reside within the channels that form in the 111 direction of the W2O6 framework and that these strongly interact. The analytical results suggest that the water and A-type cations compete for space in the tunnels within the W2O6 pyrochlore framework, with the total number of water molecules and cations being approximately constant in the six samples investigated. The interplay between the cations and water explains the non-linear dependence of the a lattice parameter on the choice of cation. It appears that the ion-exchange capacity of the material will be controlled by the amount of water initially present in the sample. Crown Copyright (C) 2011 Published by Elsevier Ltd. All rights reserved.
- ItemCation order/disorder and local structures in alkaline earth pyrochlores(International Union of Crystallography (IUCr), 2008-08-23) Thorogood, GJ; Kennedy, BJ; Peterson, VK; Elcombe, MM; Kearley, GJ; Hanna, JVMaterials that form the A2-yB2O7-x pyrochlore structure have various applications including use as catalysts, fuel cells, piezoelectrics, ferroelectric devices and ferro-magnets; have a wide range of electrical and ionic conductivities, including metallic, semi and super; can be used in nuclear-waste immobilisation due to radiation toughness, and have ion exchange properties. The degree of disorder of the A-cation is important and may play the major role in the effectiveness of these materials ion exchange properties; and contribute to the high relative permittivities displayed by (Bi,Zn)2(Zn,Nb)2O7. Previous Neutron and X-ray diffraction studies suggest that the disorder involves displacement of the A-cation along the six <112> or <110> directions. Our observation of diffuse scattering in electron diffraction patterns of CsTi0.5W1.5O6 pyrochlores suggests there are strong local correlations among the disordered ions. Movement of O at 48f away from 0.375 reduces the interaction between the two networks and so may increase the amount of disorder of the A-cation. The structures of the defect pyrochlores AAl0.33W1.67O6 where A= K, Rb or Cs have been investigated using an array of advanced structural probes; X-ray and neutron diffraction methods, NMR spectroscopy as well as the ab-initio modeling using VASP. The structures do not show a simple correlation between the radius of the A-type cation and the cubic lattice parameter. Our structural studies suggest that this may reflect the degree of local disorder of the A-cation. The results of these studies will be presented in this presentation. © 2008 International Union of Crystallography
- ItemCeramic conversion and densification of zirconium phosphonate sorbent materials(Elsevier, 2018-04-01) Veliscek-Carolan, J; Thorogood, GJ; Gregg, DJ; Tansu, M; Hanley, TLThe simple conversion of zirconium phosphonate sorbent materials, with known affinity for lanthanide elements, to durable ceramic waste forms via thermal treatment has been demonstrated. The use of zirconium phosphonate enables both removal of targeted elements from spent nuclear fuel and immobilisation into leach resistant solid products to be achieved using a single material. Thermal conversion was performed on the zirconium phosphonate both before and after loading with europium, which acted as a surrogate for the chemically similar minor actinides. Without europium loaded, the zirconium phosphonate sorbent formed predominantly KZr2(PO4)3 upon heating, independent of the processing conditions used. A maximum relative density of 87% was achieved with cold isostatic pressing (200 MPa) and sintering at 1200 °C for 12 h. When the zirconium phosphonate sorbent was loaded with europium, the phase composition formed upon thermal treatment was more complex. Specifically, mixtures of ZrP2O7, Eu0.33Zr2(PO4)3, EuPO4 and Zr2O(PO4)2 were formed, with phase compositions depending on the temperatures and pressures used. The simplest phase composition for the europium loaded material was achieved via uniaxial pressing (120 MPa) and sintering at 1300 °C for 1 h, although the ceramic pellet produced under these conditions had a relative density of only 53%. The loaded europium deported primarily to a EuPO4 phase, which is known to be highly stable and leach resistant. As such, these zirconium phosphonate materials have potential utility for treatment of nuclear wastes. © 2019 Elsevier B.V.
- ItemCharge trapping and defect segregation in quartz(AIP Publishing, 1999-06-14) Stevens Kalceff, MA; Thorogood, GJ; Short, KTIrradiation induced charging of wide band gap materials may significantly influence the development of radiation damage and associated defect migration. Charge trapped at irradiation induced and/or pre-existing defects induces a localized electric field within the irradiated volume of specimen. The powerful combination of cathodoluminescence microanalysis and electric force microscopy allows direct monitoring of the development of the irradiation induced charge distribution and its effect on the microscopic spatial segregation of defects. These techniques have been used to demonstrate the important influence of the induced local field on the microscopic defect structure of quartz. © 1999 American Institute of Physics
- ItemColor centers in K–Na–Cl crystals induced by pulsed intense relativistic electron beam at 77 K(IOP Publishing, 2022-01-25) Namioka, Y; Kurosaki, T; Kikuchi, T; Dung, DTM; Nakayama, T; Suematsu, H; Thorogood, GJIn order to reproduce the irradiation environment of Europa, NaCl-0-2mol%KCl crystals were grown and irradiated with pulsed intense relativistic electron beams at RT and 77 K in the optical absorbance spectra. The peak wavelength of the F-center was shortened by decreasing the measurement temperature and the KCl content. This phenomenon can be explained by the changes of the lattice constant and utilized to determine temperature and KCl content in the sea of Europa. © 2022 The Japan Society of Applied Physics
- ItemColor centers in NaCl single crystals induced by pulsed intense relativistic electron beams to simulate radiation bursts in Europa(IOP Publishing, 2019-03-26) Toba, R; Kikuchi, K; Imada, G; Thorogood, GJ; Hayashi, N; Maynard-Casely, HE; Suematsu, H; Nakayama, T; Suzuki, T; Niihara, KTo simulate the burst irradiation environment of Europa, single crystals of NaCl were irradiated by pulsed intense relativistic electron beams (PIREBs) with a peak energy of 6 MeV, a current of −800 A, and a pulse width of 70 ns. After irradiation, the optical absorption of the samples was measured, and results indicated that the irradiation induced F- and F2-centers. The density of F-centers was estimated to be 8.9 × 1016 cm−3 from 1 shot of PIREB irradiation with 6 MeV. The absorbed energy to form F-centers by PIREB was comparable but slightly higher than those induced by conventional direct current accelerators. The effect of pulsed heating, which should be taken into account for the detection of NaCl on Europa, is discussed. © 2019 The Japan Society of Applied Physics
- ItemComparing results of X-ray diffraction, µ-Raman spectroscopy and neutron diffraction when identifying chemical phases in seized nuclear material, during a comparative nuclear forensics exercise(Springer Nature, 2018-01-24) Rondahl, SH; Pointurier, F; Ahlinder, L; Ramebäck, H; Marie, O; Ravat, B; Delauney, F; Young, EL; Blagojevic, N; Hester, JR; Thorogood, GJ; Nelwamondo, AN; Ntsoane, TP; Roberts, SK; Holliday, KSThis work presents the results for identification of chemical phases obtained by several laboratories as a part of an international nuclear forensic round-robin exercise. In this work powder X-ray diffraction (p-XRD) is regarded as the reference technique. Neutron diffraction produced a superior high-angle diffraction pattern relative to p-XRD. Requiring only small amounts of sample, µ-Raman spectroscopy was used for the first time in this context as a potentially complementary technique to p-XRD. The chemical phases were identified as pure UO2 in two materials, and as a mixture of UO2, U3O8 and an intermediate species U3O7 in the third material. © The Author(s) 2018. This article is an open access publication.
- ItemComparison of thermal expansion of Tc and Re salts(Materials Research Society (MRS), 2017-10-29) Thorogood, GJ; Kennedy, BJ; Reynolds, EM; Poineau, F; Yu, M; Injac, S99Tc is the most significant long-lived product of uranium fission, producing the largest fraction of the total long-lived radiation emissions of nuclear waste. Tc 7+ compounds are highly mobile in the environment. Relatively little is known regarding the solid state chemistry of Tc. Recently we studied the structural properties of (NH4)TcO4 (Tc7+) and confirmed that this is isostructural with (NH4)ReO4 adopting a tetragonal scheelite type structure in space group I41/a. The unit cell parameters of (NH4)TcO4 are strongly temperature dependent with the structure showing negative thermal expansion along both the a- and c-axis, albeit at different temperatures This behavior is significantly different to that previously reported for the isostructural oxide (NH4)ReO4, although we note that the data for (NH4)ReO4 was collected at much lower resolution. Nevertheless it is clear in the literature that the thermal expansion behavior of (NH4)ReO4 is highly anisotropic. Despite the difference in the thermal expansion between what we have observed for (NH4)TcO4 and that described by others for (NH4)ReO4 it is likely that the origin of the anomalous thermal expansion in is the same in both cases, namely it is a consequence of re-orientation of the ammonium ions in the surrounding cage of eight oxygen atoms. To verify this for (NH4)TcO4 requires we replace the ammonium cation with another small cation. Therefore we have compared the thermal behavior of AReO4 with ATcO4 to determine if Re oxides are suitable surrogates to predict the behavior of Tc oxides and how they may behave in the environment.
- ItemThe composition of cement hydrating at 60 deg C from synchrotron radiation(Australian X-ray Analytical Association, 2002-07-01) Auld, J; Turner, KS; Thorogood, GJ; Ball, CJ; Aldridge, LP; Taylor, JCCement consists of 5 phases C3S, C2S, C3A, C4AF (where C denotes CaO, S denotes SiO2, A denotes AI2O3 and F denotes Fe2O3) and gypsum. When cement hydrates it forms an amorphous calcium silicate hydrate (C-S-H) as well as the crystalline ettringite and calcium hydroxide. The x-ray diffraction pattern of the hydrated cement is difficult to interpret because of its complexity. In addition, the overlapping lines from the remaining cement compounds make it difficult to quantify the amount of the crystalline components present. Using Rietveld analysis we have been able to interpret the patterns obtained from synchrotron x-ray diffraction patterns obtained at the Photon Factory at the Australian National Beamline Facility using BIGDIF. The changes in the composition of the hydrated cement paste were determined as a function of time during hydration at 60 deg C. © 2002 Australian X-ray Analytical Association Inc
- ItemCrystal chemistry and phase manipulation in Synroc(Trans Tech Publications Ltd, 1991) Vance, ER; Moricca, SA; Thorogood, GJ; Lumpkin, GRSynroc is a multi-phase ceramic designed for geological immobilisation of radioactive waste produced by reprocessing nuclear fuel from power reactors . The main crystalline phases are hollandite, perovskite, zirconolite, and reduced titanium oxide. The compositions of these phases and the nuclides they can incorporate in solid solution are shown in Table 1. Table 1. Principal Phases comprising Synroc Phase Nominal Composition Waste nuclides incorporated Estimated wt%*  Hollandite Ba1.14(Al, Tr3+)2.28Ti6O16 Cs, Sr, Rb 25 Perovskite CaTio3 Sr, RE, An 20 Zirconolite CaZrTi2O7 RE, An 20 Titanium Oxide TinO2n-1 - 35 *No HLW present RE = rare earths, An = actinides. The main (Synroc-C) formulation is designed for Purex reprocessing waste and the standard composition is wt%: Al2O3(4.3); BaO(4.4); CaO(8.8); ZrO2(5.6); TiO2(57.9); waste oxides (20). The loading of high-level waste (HLW) oxides can be varied if desired, but probably cannot exceed a value of 30-35% . Several variants of this composition have been formulated at the laboratory scale, with Synroc-D, E and F being directed towards Savannah River (U.S.A.) military waste, encapsulation of high-level nuclear reprocessing waste and unreprocessed spent fuel respectively. © 1991 Trans Tech Publications Ltd.
- ItemCrystal chemistry of the orthorhombic Ln2TiO5 compounds with Ln=La, Pr, Nd, Sm, Gd, Tb and Dy(Elsevier, 2015-07-01) Aughterson, RD; Lumpkin, GR; Thorogood, GJ; Zhang, ZM; Gault, B; Cairney, JMThe crystal structures of seven samples of orthorhombic (Pnma) Ln2TiO5 compounds with Ln=La, Pr, Nd, Sm, Gd, Tb and Dy were refined by Rietveld analysis of synchrotron X-ray powder diffraction (S-XRD) data. With increasing size of the lanthanide cation, the lattice parameters increase systematically: c by only ~1.5% whereas both a and b by ~6% from Dy2TiO5 to La2TiO5. The mean Ti–O bond length only increases by ~1% with increasing radius of the Ln cation from Gd to La, primarily due to expansion of the pair of Ti–O3 bonds to opposite corners of the Ti–O5 square based pyramid polyhedra. For Dy2TiO5 and Tb2TiO5, a significant variation in Ti–O1 and Ti–O4 bond lengths results in an increased deformation of the Ti–O5 base. The particular configuration consists of large rhombic shaped tunnels and smaller triangular tunnels along the b axis, which have implications for defect formation and migration caused by radiation damage or the ionic conductivity. © 2017 Elsevier B.V.
- ItemCrystal structure and phase transitions in the uranium perovskite, Ba2SrUO6(Elsevier, 2013-02-01) Reynolds, EM; Kennedy, BJ; Thorogood, GJ; Gregg, DJ; Kimpton, JAThe structure of one of the oxides proposed to be present in the grey phase of irradiated mixed oxide fuel, the double perovskite Ba2SrUO6 has been investigated from room temperature to 1300 K using synchrotron X-ray powder diffraction methods. The divalent strontium and hexavalent uranium are found to be fully ordered in the double-perovskite arrangement of alternating octahedra sharing corner oxygen atoms. At room temperature Ba2SrUO6 adopts a monoclinic structure in space group P21/n. Heating to above 900 K induces a first order transition to a rhombohedral structure, and further heating to above 1200 K results in a continuous transition to a cubic structure. The sequence of structures is associated with the progressive loss of cooperative tilting of the corner sharing SrO6 and UO6 octahedra. © 2012, Elsevier B.V.
- ItemDeglacial mesophotic reef demise on the Great Barrier Reef(Elsevier Science BV, 2013-12-15) Abbey, E; Webster, JM; Braga, JC; Jacobsen, GE; Thorogood, GJ; Thomas, AL; Camoin, G; Reimer, PJ; Potts, DCSubmerged reefs are important recorders of palaeo-environments and sea-level change, and provide a substrate for modem mesophotic (deep-water, light-dependent) coral communities. Mesophotic reefs are rarely, if ever, described from the fossil record and nothing is known of their long-term record on Great Barrier Reef (GBR). Sedimentological and palaeo-ecological analyses coupled with 67 C-14 AMS and U-Th radiometric dates from dredged coral, algae and btyozoan specimens, recovered from depths of 45 to 130 m, reveal two distinct generations of fossil mesophotic coral community development on the submerged shelf edge reefs of the GBR. They occurred from 13 to 10 ka and 8 ka to present. We identified eleven sedimentary fades representing both autochthonous (in situ) and allochthonous (detrital) genesis, and their palaeo-environmental settings have been interpreted based on their sedimentological characteristics, biological assemblages, and the distribution of similar modern biota within the dredges. Facies on the shelf edge represent deep sedimentary environments, primarily forereef slope and open platform settings in palaeo-water depths of 45-95 m. Two coral-algal assemblages and one non-coral encruster assemblage were identified: 1) Massive and tabular corals including Porites, Montipora and faviids associated with Lithophylloids and minor Mastophoroids, 2) platy and encrusting corals including Porites, Montipora and Pachyseris associated with melobesioids and Sporolithon, and 3) Melobesiods and Sporolithon with acervulinids (foraminifera) and bryozoans. Based on their modem occurrence on the GBR and Coral Sea and modem specimens collected in dredges, these are interpreted as representing palaeo-water depths of <60 m, <80-100 m and >100 m respectively. The first mesophotic generation developed at modern depths of 85-130 m from 13 to 10.2 ka and exhibit a deepening succession of <60 to >100 m palaeo-water depth through time. The second generation developed at depths of 45-70 m on the shelf edge from 7.8 ka to present and exhibit stable environmental conditions through time. The apparent hiatus that interrupted the mesophotic coral communities coincided with the timing of modem reef initiation on the GBR as well as a wide-spread flux of siliciclastic sediments from the shelf to the basin. For the first time we have observed the response of mesophotic reef communities to millennial scale environmental perturbations, within the context of global sea-level rise and environmental changes. © 2013, Elsevier Ltd.