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  1. No Access

    Article

    Raman spectroscopy, vibrational analysis, and heating of buergerite tourmaline

    Polarized Raman spectra were collected for single crystal buergerite (NaFe3Al6(BO3)3Si6O18(O0.92(OH)0.08)3F) from room temperature to near 1,375°C. Vibrational assignments to features in the room temperature spec...

    David A. McKeown in Physics and Chemistry of Minerals (2008)

  2. Article

    Thermoelectric Properties of NaCo2 − x Fe x O y

    Biprodas Dutta, Jugdersuren Battogtokh, David A. McKeown… in Journal of Electronic Materials (2007)

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  3. No Access

    Article

    Tc and Re Behavior in Borosilicate Waste Glass Vapor Hydration Tests

    Technetium (Tc), found in some nuclear wastes, is of particular concern with regard to long-term storage, because of its long-lived radioactivity and high mobility in the environment. Tc and rhenium (Re), comm...

    David A. McKeown, Andrew C. Buechele, Wayne W. Lukens… in MRS Online Proceedings Library (2007)

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    Article

    X-ray Absorption Fine Structure Studies of Speciation of Technetium in Borosilicate Glasses

    A series of glass samples were prepared analogously to high level waste glass using either glass frit or glass precursors combined with a high level waste surrogate containing NaTcO4. Three different technetium s...

    Wayne W. Lukens, David K. Shuh, Isabelle S. Muller… in MRS Online Proceedings Library (2003)

  5. No Access

    Article

    Vibrational analysis of palygorskite and sepiolite

    Lattice dynamic calculations for the sepiolite and palygorskite structures using polarized Raman and FTIR spectra provide a fundamental basis for interpreting spectral features by assigning vibrational modes. ...

    David A. McKeown, Jeffrey E. Post, Edgar S. Etz in Clays and Clay Minerals (2002)

  6. No Access

    Article

    X-ray Absorption Studies of Vanadium Valence and Local Environment in Borosilicate Waste Glasses

    XANES and EXAFS data were collected and analyzed to characterize vanadium in borosilicate glasses used for immobilization of sulfur-containing nuclear wastes. Earlier studies suggested that adding vanadium to ...

    David A. McKeown, Isabelle S. Muller, Keith S. Matlack… in MRS Online Proceedings Library (2002)

  7. No Access

    Article

    Formulation, Testing, and Structural Characterization of High-Zirconium High-Level Waste Glasses

    A range of compositions of high-zirconia borosilicate glasses were formulated and their structures investigated by a combination of techniques. These compositions have potential applications for high-level nuc...

    David A. McKeown, Isabelle S. Muller, Andrew C. Buechele… in MRS Online Proceedings Library (1999)

  8. No Access

    Article

    Linked four-membered silicate rings: vibrational analysis of Gillespite

    Raman spectra and lattice dynamics calculations are presented for the silicate mineral gillespite, BaFeSi4O10, which contains sheets of linked four-membered silicate rings. The results are analyzed in relation to...

    David A. McKeown, Michael I. Bell in Physics and Chemistry of Minerals (1998)

  9. No Access

    Article

    Vibrational analysis of dioptase Cu6Si6O18 · 6(H2O) and its puckered six-membered ring

    The normal modes of vibration and their frequencies are calculated for dioptase, a mineral whose crystal structure (space group R $$\...

    David A. McKeown, Charles C. Kim, Michael I. Bell in Physics and Chemistry of Minerals (1995)

  10. No Access

    Article

    X-ray Absorption Spectroscopic Study of Copper in an Amorphous Copper-Silicate: Chrysocolla

    XANES and EXAFS data indicate that chrysocolla does not contain domains of Cu-metal or Cu-oxides as previously hypothesized, but is most similar to dioptase, a chemically homogeneous crystalline Cu-silicate. T...

    David A. McKeown in MRS Online Proceedings Library (1993)

  11. No Access

    Article

    X-ray Absorption Analysis of Ge and Ga Environments in Ba-Gallogermante Glasses

    X-ray absorption spectroscopy has been used to characterize the local structure surrounding Ga and Ge in BaO-Ga2O3-GeO2 glasses. Based on comparisons with results for crystalline standards of known structure, Ge ...

    Celia I. Merzbacher, David A. McKeown in MRS Online Proceedings Library (1993)

  12. No Access

    Article

    Aluminum X-ray absorption near-edge spectra of some oxide minerals: Calculation versus experimental data

    Al X-ray absorption K-edge spectra were calculated for atom clusters which simulate Al surrounded by oxygens in tetrahedral and octahedral environments in five minerals, and are compared with experimental Al K...

    David A. McKeown in Physics and Chemistry of Minerals (1989)

  13. No Access

    Chapter and Conference Paper

    Local Coordination Environment of Na in a Series of Silica-Rich Glasses and Selected Minerals Within the Na2O-Al2O3-SiO2 System

    Photoelectron total yield Na EXAFS spectra were gathered on the JUMBO mono-chromator line at SSRL to characterize the Na environment for a collection of Na2O-Al2O3-SiO2 minerals and glasses. Included in the colle...

    David A. McKeown, Gordon E. Brown Jr.… in EXAFS and Near Edge Structure III (1984)