Browsing by Author "Izaola, Z"

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    Diffuse scattering and QENS study of copper chalcogenides
    (Australian Institute of Physics, 2009-02-05) Danilkin, SA; Avdeev, M; Studer, AJ; Ling, CD; Macquart, RB; Russina, M; Izaola, Z
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    High water diffusivity in low hydration plasma-polymerised proton exchange membranes
    (Trans Tech Publications, 2010-08-02) Peterson, VK; Corr, CS; Kearley, GJ; Boswell, RW; Izaola, Z
    This paper compares proton diffusion through plasma-polymerised proton-exchange membranes (PEMs) produced using traditional wet-chemical methods (Nafion®) and those produced using plasma-polymerisation. Using quasielastic neutron scattering and a simple model of proton motion we find the measured diffusion-rate of protons in the plasma-polymerised material and Nafion® is the same (within 1 standard error) even though the plasma-polymerised membrane has 80% less water than the Nafion®. We attribute this result to the highly cross-linked structure of the plasma-polymerised membrane.
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    Neutron scattering study of short-range correlations and ionic diffusion in copper selenide
    (Springer, 2011-02-01) Danilkin, SA; Avdeev, M; Sakuma, T; Macquart, RB; Ling, CD; Russina, M; Izaola, Z
    The paper reports the results of a neutron scattering study of Cu(2-delta)Se superionic compounds. The crystallographic model fitted to the diffraction data shows the occupation of 8c and 32f sites by Cu atoms. Observed diffuse background is related to correlated thermal vibrations of Se and Cu atoms, with Sea dagger"Cu (8c,32f) and Cu (8c)a dagger"Cu (8c) correlations being most important. The quasi-elastic neutron experiments show the decrease of the self-diffusion coefficient with the deviation from the stoichiometry due to the longer residence time of Cu ions between diffusion hops. Combination of neutron diffraction, diffuse scattering and quasi-elastic scattering experimental data suggests that the Cu atoms diffuse between the nearest 8c sites through the 32f sites. © 2011, Springer.
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    Quasi-elastic neutron scattering study of diffusion in Cu-Se superionic conductor
    (Malaysian Nuclear Agency, 2009-06-29) Danilkin, SA; Avdeev, M; Ling, CD; Macquart, RB; Russina, M; Izaola, Z
    Copper selenide is a mixed ionic-electronic conductor and received attention from the technological and physical point of view in particular due to a high ionic conductivity. According to [1, 2] only a fraction of Cu atoms takes part in the ionic transport in Cu{sub 2-x}Se compounds: the number of mobile atoms is about 1/3 - 1/8 of the total cation concentration in stoichiometric Cu{sub 2}Se and decreases with x causing the ionic conductivity to drop. This conclusion was based on the assumption that Cu mobility does not depend on composition. Therefore the QENS study is of interest because the width and intensity of quasi-elastic peak associated with Cu diffusion are directly related to Cu coefficient of self-diffusion and the number of mobile ions, respectively. This paper presents results of QENS measurements performed on Cu{sub 1.77}Se, Cu{sub 1.90}Se and Cu{sub 1.98}Se compounds at 313 and 430 K. We found that in Cu{sub 1.98}Se the quasielastic component is not observed in ordered non-superionic {alpha}-phase at T = 313 K, however it is clearly seen in superionic {beta}-phase at T=430 K. By contrast the Cu{sub 1.77}Se compound which is superionic at ambient temperature has relatively small quasielastic component showing little difference between 313 and 430 K. The analysis shows that fraction of Cu atoms which takes part in the ionic transport indeed decreases with x in general agreement with papers [1, 2], but not vanishes at x = 0.23. [1] R.A. Yakshibaev et al., Sov. Phys. Solid State, 26 2189 (1984) [2] M.A. Korzhuev, Phys. Solid State 40 217 (1998)
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    Superfast proton diffusion achieved in a plasma-polymerized fuel-cell membrane
    (American Chemical Society, 2013-03-07) Peterson, VK; Corr, CS; Boswell, RW; Izaola, Z; Kearley, GJ
    We measure superfast proton diffusion in a proton-exchange membrane (PEM) produced by plasma polymerization. The proton self-diffusion is measured in water-saturated PEMs from the proton autocorrelation function obtained from quasielastic neutron scattering (QENS). 41(3)% of protons in the plasma-produced membrane diffuse at a rate that is an order of magnitude faster than that measured in the commercially available membrane, Nafion, and this is achieved in low hydration conditions. Both molecular dynamic simulations and experimental results are consistent with an assisted superfast diffusion process that may open the way to more powerful fuel cells. © 2013, American Chemical Society.