Browsing by Author "Wang, YD"

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    Direct observation of charge order and an orbital glass state in multiferroic LuFe2O4
    (American Physical Society, 2009-08-14) Mulders, AM; Lawrence, SM; Staub, U; García-Fernández, M; Scagnoli, V; Mazzoli, C; Pomjakushina, E; Conder, K; Wang, YD
    Geometrical frustration of the Fe ions in LuFe2O4 leads to intricate charge and magnetic order and a strong magnetoelectric coupling. Using resonant x-ray diffraction at the Fe K edge, the anomalous scattering factors of both Fe sites are deduced from the (h/3 k/3 l/2) reflections. The chemical shift between the two types of Fe ions equals 4.0(1) eV corresponding to full charge separation into Fe2+ and Fe3+. The polarization and azimuthal angle dependence of the superlattice reflections demonstrate the absence of differences in anisotropic scattering revealing random orientations of the Fe2+ orbitals characteristic of an orbital glass state. © 2009, American Physical Society
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    Localisation of trace metals in hyperaccumulating plants using μ-PIXE
    (Australian Institute of Nuclear Science and Engineering (AINSE), 2007-11) Siegele, R; Kachenko, AG; Wang, YD; Ionescu, M; Bhatia, NP; Cohen, DD
    PIXE is a very sensitive technique that can fast and reliably measure a wide range of elements simultaneously with high sensitivity. Using a focused microbeam elemental distributions can be mapped with high spatial resolution. We demonstrate high resolution mapping of metals in plant leafs at 5 um resolution and it's application in detecting sites of metal accumulation in metal-accumulating plant tissues. The importance of biological sample preparation is discussed by direct comparison of freeze-substitution and freeze-drying routinely used in biological sciences. The advantages and limitations of quantitative elemental imaging using these techniques are also discussed.
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    Localisation of trace metals in metal-accumulating plants using μ-PIXE
    (Wiley-Blackwell, 2008-03) Siegele, R; Kachenko, AG; Bhatia, NP; Wang, YD; Ionescu, M; Singh, B; Baker, AJM; Cohen, DD
    Particle induced x-ray emission (PIXE) is a very sensitive technique that can quickly and reliably measure a wide range of elements simultaneously with high sensitivity. Using a focused microbeam, elemental distributions can be mapped with high spatial resolution. We demonstrate high-resolution mapping of metals in plant leaves at 5 mu m resolution and its application in detecting sites of metal accumulation in metal-accumulating plant tissues. The importance of biological sample preparation is discussed by direct comparison of freeze-substitution and freeze-drying techniques routinely used in biological sciences. The advantages and limitations of quantitative elemental imaging using these techniques are also discussed. © 2008, Wiley-Blackwell.
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    Micrometer-Scale 2D Mapping of the Composition and Homogeneity of Polymer Inclusion Membranes
    (CSIRO Publishing, 2011) St John, AM; Best, SP; Wang, YD; Tobin, MJ; Puskar, L; Siegele, R; Cattrall, RW; Kolev, SD
    A new method for determining variations in composition at the micrometer level of polymer inclusion membranes (PIMs) using synchrotron-based Fourier-transform infrared (FTIR) microspectrometry is described and used to investigate the relationship between PIM composition and the reproducibility of formation of optically clear, 'homogeneous' polymer membranes. Membranes based on Aliquat 336 and poly(vinyl chloride) (PVC), di(2-ethylhexyl) phosphoric acid and PVC, and Aliquat 336 and cellulose triacetate give highly reproducible PIMs with excellent optical properties which are chemically homogeneous on the micrometer scale. The close relationship between the spatial distribution of the extractant in the PIM and the extracted species was demonstrated by proton-induced X-ray emission microspectrometry (mu-PIXE) examination of chemically homogeneous membranes loaded with uranium. There is a high correlation between the homogeneity of the distributions of extracted uranium, polymer, and extractant, both on the surface of the PIM and over its cross-section. This approach provides a quantitative basis for the evaluation and optimization of PIMs and similar composite materials. © 2011, CSIRO Publishing
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    Rheology of ε-iron up to 19 GPa and 600 K in the D-DIA
    (American Geophysical Union, 2007-12-07) Nishiyama, N; Wang, YD; Rivers, ML; Sutton, SR; Cookson, DJ
    Stress-strain curves, i.e., relations between the differential stress and macroscopic sample strain, of polycrystalline ε-iron have been obtained at pressures of 17(±1) GPa, three different temperatures (600, 400, and 300 K), and various strain rates between 3.8 × 10−6 and 2.3 × 10−5 s−1 using the deformation-DIA coupled with monochromatic X-rays. Five independent stress-strain curves were obtained on axial shortening and the sample exhibited ductile behavior in all. Above 4% axial strain, sample stresses reach saturation and the sample exhibited steady-state deformation. Stress exponents at temperatures of 400 and 600 K were determined to be ∼31 and ∼7, respectively. These results indicate that ε-iron deforms in plasticity regime below 400 K and that the dominant deformation mechanism at 600 K may be low temperature power-law creep. The overall deformation behavior for ε-iron is consistent with that of zinc, suggesting that the deformation mechanism map of ε-iron resembles those of other hexagonal metals. © 2007, American Geophysical Union