Browsing by Author "Ball, CJ"
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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
- ItemCell parameters and the orthorhombic to cubic transformation in strontium substituted perovskite (CaTiO3)(Australian and New Zealand Institutes of Physics, 1994-02-10) Ball, CJ; Begg, BD; Vance, ERThe departure of the orthorhombic unit cell of perovskite (CaTiO3) from the cubic symmetry can be characterised by the angle of shear, ∅ of the pseudo-cubic sub-cell. We have determined ∅ for a series of strontium-substituted perovskites, of general formula Cai-xSrxTiO3, at room temperature. ∅ decreases linearly with increases in x and extrapolates to zero at x ≈ 0.4, in fair agreement with previous work. For x > 0.4 the structure is cubic, contrary to previous reports.
- 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
- ItemHigh-temperature study of CaZrTi2O7(Elsevier, 1992-08-02) Vance, ER; Cassidy, DJ; Ball, CJ; Thorogood, GJPreviously reported anomalous thermal expansion effects in the 1200–1500°C range for hot-pressed CaZrTi2O7 were shown to be due to irreversible bloating effects, from occluded gases. X-ray diffraction and differential thermal analysis of ordered CaZrTi2O7 did not reveal evidence of a solid-state transformation at temperatures up to 1450°C. © 1992 Elsevier
- ItemIncorporation of uranium in zirconolite (CaZrTi2O7)(John Wiley & Sons, Inc, 2002-07) Vance, ER; Lumpkin, GR; Carter, ML; Cassidy, DJ; Ball, CJ; Day, RA; Begg, BDUp to 0.15 formula unit (f.u.) of U4+ incorporated in the Zr site of zirconolite by firing CaUxZr(1−x)Ti2O7 compositions in argon at 1400°C allows retention of the 2M polytype. Further U4+ substitution for Zr, up to 0.4 f.u., produces the 4M polytype (containing ∼0.4 f.u. of U) plus the 2M polytype containing 0.15 f.u. of U. The pyrochlore structure (containing 0.6 f.u. of U) forms in conjunction with the 4M polytype at U contents of 0.4 f.u. up to 0.7 f.u. Higher U contents give the pyrochlore structure, but the solid-state reactivity of even alkoxide-based preparations becomes increasingly poor for x > ∼0.7 and hot pressing in graphite dies at ∼1250°C is necessary to achieve near single-phase pyrochlore structures for x= 1. When samples of CaUxZr1−xTi2O7 stoichiometry (x= 0.1 and 0.2) are oxidized at 1400°C in air, diffuse reflectance spectroscopy (DRS) shows evidence for U5+ formation at the expense of U4+ via enhanced absorption bands, ∼50 nm in half-width, near 970 and 1500 nm and correspondingly weakened absorption at 1150 and 1660 nm. Weight gains consistent with complete oxidation of U4+ to U5+ are observed when finely powdered argon-fired samples with x= 0.1 and 0.4 are heated in air to 1200°C. Evidence for U valence states higher than +4 in both argon- and air-heated materials containing charge compensators to encourage U5+ or U6+ formation was also derived from DRS (showing U5+ in particular), and XANES. DRS shows weak absorption bands attributable to U4+ in zirconolites containing ∼0.2 f.u. of U incorporated in the Ca site via Mg or Al substitutions in the Ti sites, with the spectrum being closely but not exactly similar to that attributed to U4+ in the Zr site. Zirconolite and pyrochlore compositions which are melted at 1500° or 1550°C in argon and furnace-cooled yield broadly similar phase assemblages to the corresponding sintered materials, but there is evidence of incongruent melting in all materials. © 2002 The American Ceramic Society
- ItemIndexing reflections obtained with a four-circle diffractometer(Australian Atomic Energy Commission, 1979-11) Ball, CJA procedure for indexing reflections obtained when setting up a crystal on a four-circle diffractometer is described, together with a computer program which has been written for implementing part of the procedure.
- ItemInterface phenomena in synroc, a titanate-based nuclear waste ceramic(Elsevier, 1995) Vance, ER; Ball, CJ; Blackford, MG; Day, RA; Lumpkin, GR; Smith, KL; Hart, KP; McGlinn, PJ; Thorogood, GJSeveral aspects of Synroc which fall into the broad class of interface phenomena are discussed. These are radiation damage processes which give rise to interfaces between damage tracks and neighbouring unirradiated material, intergranular films which have deleterious effects on chemical durability, and aqueous leaching of Synroc which takes place primarily at the interface between the solid and groundwater. © 1995 Elsevier B.V.
- ItemPu, U, and Hf incorporation in Gd silicate apatite(John Wiley & Sons, Inc, 2004-12-20) Vance, ER; Ball, CJ; Begg, BD; Carter, ML; Day, RA; Thorogood, GJTrivalent Pu can be incorporated in the silicate apatite structure to form Ca2Pu8(SiO4)6O2 by sintering under reducing conditions, while the incorporation of tetravalent Pu in the Ca/rare earth sites in oxidizing or neutral conditions is limited to only 0.6 formula units (f.u.). The d-spacings and intensities of the X-ray pattern of hexagonally structured Ca2Pu8(SiO4)6O2 after firing at 1250°C are given, and the a and c lattice parameters are 0.95611 and 0.70281 nm, respectively. The respective solid solubility limits of U and Hf in Ca2Gd8–x(U/Hf)x(SiO4)6O2 apatite samples were 0.3 and 0.2 f.u. © 2004 The American Ceramic Society
- ItemStructures in the system CaTiO3/SrTiO3(Elsevier, 1998-09) Ball, CJ; Begg, BD; Cookson, DJ; Thorogood, GJ; Vance, ERAt room temperature the sequence of phases with increasing amounts of strontium in the system CaTiO3/SrTiO3is orthorhombic (Pnma), orthorhombic (Bmmb), tetragonal (I4/mcm), and cubic (Pm3m). All phase boundaries shift toward smaller strontium contents with increase of temperature. Volume changes resulting from phase transformations are small for all compositions. Shape changes are greatest (∼0.3%) for theBmmb/I4/mcmtransition, but would probably be accommodated by microtwinning and so are unlikely to affect the mechanical integrity of a specimen. ©1998 Academic Press
- ItemTables relating to texture in materials with cubic crystal symmetry(Australian Atomic Energy Commission, 1979-07) Ball, CJTables have been prepared giving: 1. the coefficients of augmented Jacobi polynomials to order 22; 2. the relations between coefficients of associated Legendre polynomials used to represent pole figures and the coefficients of the augmented Jacobi polynomials that represent the corresponding crystallite orientation distribution function, for various sets of lattice planes; 3. The relations between coefficients of augmented Jacobi polynomials representing crystallite orientation distribution functions before and after transformation according to three common transformation laws.
- ItemTexture determination with a four-circle diffractometer(Australian Atomic Energy Commission, 1979-05) Ball, CJA fully automatic method of plotting pole figures, using data obtained with a computer-controlled four-circle diffractometer, is described.
- ItemThermal expansion coefficients of zirconolite (CaZrTi2O7) and perovskite (CaTiO3) from x-ray powder diffraction analysis(Elsevier, 1992-08-02) Ball, CJ; Thorogood, GJ; Vance, ERThe thermal expansion coefficients of zirconolite, both ordered and disordered, and perovskite, were measured by X-ray powder diffraction analysis in the temperature range 25–1200°C. The principal results are: (1) The mean thermal expansion coefficients (K−1) of ordered zirconolite are:αa = (11.35±0.25) × 10−6;αb = (8.72± 0.22) × 10−6;αc = (10.0 ±0.5) × 10−6. (2) The mean thermal expansion coefficients (K−1) of disordered zirconolite areα∥ = (9.89±0.15) × 10−6 in the (001) plane and α⊥ = (9.37±0.14) × 10−6 normal to (001). (3) The mean thermal expansion coefficients (K−1) of perovskite are:αa = (7.86±0.30) × 10−6;αb = (13.46±0.17) × 10−6;α c = (16.55±0.26) × 10−6. © 1992 Published by Elsevier B.V.
- ItemThe use of internal standards for measurement of temperature in BigDiff(Australian Institute of Physics, 2002-01-29) Ball, CJ; Thorogood, GJA simple furnace has been constructed to enable X-ray diffractograms to be obtained at elevated temperatures in BigDiff, on the Australian beamline at the Photon Factory, Tsukuba, Japan. Measurement of the specimen temperature presents a problem, and this poster describes an attempt to measure the temperature using the thermal expansion of an internal standard. α-alumina was chosen as the internal standard, but because of uncertainty regarding its coefficients of thermal expansion it was decided to compare temperatures based on α-alumina with those based on tungsten, using a composite specimen. Data in BigDiff are recorded on image plates. It has long been known that the direction of reading of an image plate is not strictly parallel to its edge, with the result that the starting angles of strips across the width of a plate are not exactly the same. To overcome this problem exposures at the same temperature were recorded on opposite sides of the plate. Comparison of these diffractograms revealed that the pixel spacing also varied across the width of the plate, and down the length of a strip. As a result it was not possible to calculate cell parameters with sufficient accuracy using Rietveld refinement of the data. Instead, temperatures have been calculated from the shifts of individual lines from their supposed positions at the reference temperature. Comparing temperatures calculated from different lines showed that at each temperature the entire pattern had been shifted parallel to its length by an amount on the order of 50 μm, but not the same for all patterns, presumably because movement of the cassette in BigDiff was not strictly parallel to the guide rails. After making allowance for the above effects temperatures can be measured to a precision of ±2K, but the biggest uncertainty, almost an order of magnitude greater, remains lack of knowledge of the coefficients of thermal expansion.
- ItemAn x-ray investigation of austenite reversion in maraging steels(Australian Atomic Energy Commission, 1984-04) Ball, CJReversion of martensite to austenite in maraging steels has been investigated in the range 400 to 800oC. Austenite formed at temperatures up to ~680oC does not transform back to martensite on cooling to room temperature, and the amount of such austenite is, in some cases, greater than 65 per cent. Lattice parameter measurements indicates that substantial amounts of molybdenum and/or titanium remain in solutions after completion of the age-hardenin precipitation reaction, and that the solubility of these elements is greater in austenite than in martensite at temperatures of ~700oC.
- ItemThe x-ray powder diffraction pattern and lattice parameters of perovskite(Australian Nuclear Science and Technology Organisation, 1988-02) Ball, CJ; Napier, JGThe interplanar spacings and intensities of all lines appearing in the X-ray powder diffraction pattern of perovskite have been calculated. Many of the lines occur in groups with a large amount of overlap. As an aid to identifying the lines which are observed the intensity profiles of the major groups have been plotted. Those lines which are relatively free of overlap and can be identified unambiguously have been used to calculate the lattice parameters with the results a=5.4424 +- 0.0001 A b=7.6417 +- 0.0002 A c=5.3807 +- 0.0001 A.