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Brady, Steven K.; Conradi, Mark S.; Majer, G.; Barnes, R. G.

doi:10.1103/physrevb.72.214111

Cited by 21 publications

(32 citation statements)

References 15 publications

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“…For Schoepite, the best fit voltammogram yields D CT values of 6 10 À14 cm 2 s À1 and 1 10 À14 cm 2 s À1 for the UO 2 2 + /UO 2 + and UO 2 + /U 4 + couples, respectively, whilst the values for the other minerals are collated in Table 1. This slow homogeneous charge transport rate is typical of minerals [39] and suggests that ion rather than electron movement limits the overall rate of charge transport. Significantly, this D CT is a lot lower than we previously reported for solid deposits of Studtite, 1.2 AE 0.4 10 À11 cm 2 s À1 .…”

Section: Mineralmentioning

confidence: 99%

Redox Processes in Solid‐State Uranyl (Oxy)hydroxide Minerals

et al. 2017

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The correlation between the structure of a series of uranyl minerals of the type [(UO2)8O2(OH)12] and M[(UO2)xOy(OH)z] (M=Na, x=4, y=2, z=5; M=K2, x=6, y=4, z=6; M=Ca, x=6, y=4, z=6), and their electrochemical properties have been investigated by using solid‐state cyclic voltammetry. Solid‐state electrochemical investigations at near‐neutral pH values reveal that all minerals undergo redox reactions in the potential range from −0.72 to −0.91 V vs. Ag/AgCl. This process is assigned to the U(VI)/U(V) redox couple and a further reduction, observed between −0.95 and −1.20 V, is associated with the U(V)/U(IV) reduction. The nature of the reduced products has been probed by using vibrational spectroscopy and SEM−EDX, and was found to be UO2+x. The mechanism of reduction has been elucidated and shown to be dominated by two independent one‐electron transfer reactions with disproportionation playing at most a minor role. The rate of charge propagation through the solid deposits, characterized by the homogeneous charge‐transport diffusion coefficient, DCT, is much lower in these minerals than structurally related systems with ion, rather than electron, transfer being rate limiting. Overall, the insights into the nature and rate of redox conversion suggest that the uranyl minerals formed by the oxidative corrosion of spent nuclear fuels are not electrochemically innocent.

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Section: Mineralmentioning

confidence: 99%

Redox Processes in Solid‐State Uranyl (Oxy)hydroxide Minerals

et al. 2017

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“…The FIDs were extrapolated back to time zero using a Gaussian function, to replace the early signals that were corrupted by probe ringing and receiver recovery. 17 These corrections and precautions are only important 65 for very broad signals (broader than 30 kHz), as observed here at low temperatures. The hydrogen spin-lattice relaxation time T 1 was measured by the saturate-wait-inspect strategy.…”

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confidence: 92%

Thermolysis and solid state NMR studies of NaB₃H₈, NH₃B₃H₇, and NH₄B₃H₈

et al. 2013

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In an effort to broaden the search for high-capacity hydrogen storage materials, three triborane compounds, NaB3H8, NH 3B3H7, and NH4B3H 8, were studied. In addition to hydrogen, thermal decomposition also releases volatile boranes, and the relative amounts and species depend on the cations (Na+, NH4 +) and the Lewis base (NH 3). Static-sample hydrogen NMR is used to probe molecular motion in the three solids. In each case, the line width decreases from low temperatures to room temperature in accordance with a model of isotropic or nearly isotropic reorientations. Such motions also explain a deep minimum in the relaxation time T1. Translational diffusion never appears to be rapid on the 10 -5 s time scale of NMR. In an effort to broaden the search for high-capacity hydrogen storage materials, three triborane compounds, NaB 3 H 8 , NH 3 B 3 H 7 , and NH 4 B 3 H 8 , were studied. In addition to hydrogen, thermal decomposition also releases volatile boranes, and the relative amounts and species depend on the cations (Na + , NH 4 + ) and the Lewis base (NH 3 ). Static-sample hydrogen NMR is used to probe molecular motion 10 in the three solids. In each case, the line width decreases from low temperatures to room temperature in accordance with a model of isotropic or nearly isotropic reorientations. Such motions also explain a deep minimum in the relaxation time T 1 . Translational diffusion never appears to be rapid on the 10 -5 s time scale of NMR.

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“…How to handle the obscured portion of the FID following the excitation pulse is an issue in Fourier analysis. 10) The time shifting of a single exponential FID placed at zero time leads to a Lorentzian spectrum regardless of the zero. However, a time-shifted Gaussian decay does not lead to a simple Gaussian lineshape.…”

Section: Introductionmentioning

confidence: 99%

Intrinsic Proton NMR Studies of Mg(OH)₂ and Ca(OH)₂

Itoh¹,

Isobe²

2016

J. Phys. Soc. Jpn.

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We studied the short proton free induction decay signals and the broad 1 H NMR spectra of Mg(OH) 2 and Ca(OH) 2 powders at 77−355 K and 42 MHz using pulsed NMR techniques. Using a Gaussian-type back extrapolation procedure for the obscured data of the proton free induction decay signals, we obtained more precise values of the second moments of the Fourier-transformed broad NMR spectra than those in a previous report [Y. Itoh and M. Isobe, J. Phys. Soc. Jpn. 84, 113601 (2015)] and compared with the theoretical second moments. The decrease in the second moment could not account for the large decrease in the magnitude of the intrinsic proton spin-lattice relaxation rate 1/T 1 from Mg(OH) 2 to Ca(OH) 2 . The analysis of 1/T 1 ∝ exp(−E g /k B T ) with E g ∼ 0.01 eV points to a local hopping mechanism, and that of 1/T 1 ∝ T n with n ∼ 0.5 points to an anharmonic rattling mechanism.

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Proton magnetic resonance spectra ofYH3andLuH3

Cited by 21 publications

References 15 publications

Redox Processes in Solid‐State Uranyl (Oxy)hydroxide Minerals

Redox Processes in Solid‐State Uranyl (Oxy)hydroxide Minerals

Thermolysis and solid state NMR studies of NaB₃H₈, NH₃B₃H₇, and NH₄B₃H₈

Intrinsic Proton NMR Studies of Mg(OH)₂ and Ca(OH)₂

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Proton magnetic resonance spectra ofYH3andLuH3

Cited by 21 publications

References 15 publications

Redox Processes in Solid‐State Uranyl (Oxy)hydroxide Minerals

Redox Processes in Solid‐State Uranyl (Oxy)hydroxide Minerals

Thermolysis and solid state NMR studies of NaB3H8, NH3B3H7, and NH4B3H8

Intrinsic Proton NMR Studies of Mg(OH)2 and Ca(OH)2

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Product

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Thermolysis and solid state NMR studies of NaB₃H₈, NH₃B₃H₇, and NH₄B₃H₈

Intrinsic Proton NMR Studies of Mg(OH)₂ and Ca(OH)₂