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Browsing Journal Articles by Author "Ablott, TA"

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    Boson peak in ultrathin alumina layers investigated with neutron spectroscopy
    (American Physical Society, 2020-06-11) Cortie, DL; Cyster, MJ; Ablott, TA; Richardson, C; Smith, JS; Iles, GN; Wang, XL; Mitchell, DRG; Mole, RA; de Souza, NR; Yu, DH; Cole, JH
    Bulk glasses exhibit extra vibrational modes at low energies, collectively known as the boson peak. The vibrational dynamics in nanoscale alumina glasses have an impact on the performance of qubits and other superconducting devices; however, the frequency of the boson peak has not been previously measured. Here we report neutron spectroscopy experiments on Al/Al2O3 nanoparticles consisting of spherical metallic cores with a radii from 20 to 1000 nm surrounded by a 3.5-nm-thick alumina glass. A low-energy peak is observed at ωBP = 2.8 ± 0.6 meV for highly oxidized particles, indicating an excess in the density of states. The intensity of the peak scales inversely with particle size and oxide fraction, indicating a surface origin, and is redshifted by 3 meV with respect to the van Hove singularity of γ -phase Al2O3 nanocrystals. Molecular-dynamics simulations of α-Al2O3, γ -Al2O3 and α-Al2O3 show that the observed boson peak is a signature of the ultrathin glass surface and the characteristic frequency is reduced compared to the peak in the bulk glass. © 2020 The Authors. Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license.
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    Exploring the influence of pH on the structural intricacies of uranium oxide hydrates containing both Cd(ii) and K(i) ions
    (Royal Society of Chemistry, 2023-05-28) Ablott, TA; Lu, KT; Wei, T; Zhang, YJ
    We report the synthesis of two new dual-cation uranium oxide hydrate (UOH) materials, containing both Cd2+ and K+ ions, along wxrith their characterisation by means of single-crystal X-ray diffraction and a range of other structural and spectroscopic techniques. The materials were found to differ in structures, topology and uranium to cation ratios, with the layered UOH-Cd crystallising in a plate morphology and containing a U : Cd : K ratio of 3 : 1.5 : 1. Conversely, the framework-type UOF-Cd incorporates much less Cd, with a U : Cd : K ratio of 4.4 : 0.2 : 1 and is found as needle-like crystals. A common feature in both structures is the presence of β-U3O8 type layers with a distinct uranium centre which lacks the expected uranyl bonds, highlighting the importance of the β-U3O8 layer in the subsequent self-assembly and preferential formation of a variety of structural types. Most importantly, by exploiting the additional flexibility provided by monovalent cation species (i.e., K+) as secondary metal cations to synthesise these novel dual-cation materials, this work highlights the potential for broadening the scope of viable synthetic UOH phases towards furthering the understanding of these systems in their roles as alteration products in the surrounds of spent nuclear fuel in deep geological repositories. © The Authors - Open Access CC BY Licence
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    Synthesis and structure of oxygen deficient lead-technetium pyrochlore, the first example of a valence V technetium oxide
    (Frontiers Media, 2021-07-01) Kennedy, BJ; Ablott, TA; Avdeev, M; Carter, ML; Losurdo, L; Saura-Múzquiz, M; Thorogood, KJ; Ting, J; Wallwork, KS; Zhang, ZM; Zhu, HL; Thorogood, GJ
    The structure of lead-technetium pyrochlore has been refined in space group F d 3 ¯ m with a = 10.36584(2) Å using a combination of synchrotron X-ray and neutron powder diffraction data and confirmed via Electron Diffraction. The oxide is found to be oxygen deficient with a stoichiometry of Pb2Tc2O7-d. Displacive disorder of the Pb cations is evident from the refinements, as has been observed in Bi2Tc2O7-d. X-ray absorption spectroscopic measurements at the Tc K-edge demonstrate the valence of the Tc is greater than 4.0 as anticipated from the refined oxygen stoichiometry. Raman spectroscopy confirms the presence of disorder leading us to conclude that this pyrochlore is the first example of a valence V technetium oxide. © 2021 Kennedy, Ablott, Avdeev, Carter, Losurdo, Saura-Muzquiz, Thorogood, Ting, Wallwork, Zhang, Zhu and Thorogood. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY).