Surface oxide on thin films of yttrium hydride studied by neutron reflectometry

The applicability of standard methods for compositional analysis is limited for H-containing films. Neutron reflectometry is a powerful, non-destructive method that is especially suitable for these systems due to the large negative scattering length of H. In this work we demonstrate how neutron reflectometry can be used to investigate thin films of yttrium hydride. Neutron reflectometry gives a strong contrast between the film and the surface oxide layer, enabling us to estimate the oxide thickness and oxygen penetration depths. A surface oxide layer of 5-10 nm thickness was found for unprotected yttrium hydride films

Rare Earth Borohydrides—Crystal Structures and Thermal Properties

Rare earth (RE) borohydrides have received considerable attention during the past ten years as possible hydrogen storage materials due to their relatively high gravimetric hydrogen density. This review illustrates the rich chemistry, structural diversity and thermal properties of borohydrides containing RE elements. In addition, it highlights the decomposition and rehydrogenation properties of composites containing RE-borohydrides, light-weight metal borohydrides such as LiBH4 and additives such as LiH

Structural transitions and magnetocaloric properties of low-cost MnNiSi-based intermetallics

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Deuterium Exchange Dynamics in Zr_2NiD_(4.8) Studied by ^2H MAS NMR Spectroscopy

Variable temperature (VT) ^2H magic angle spinning (MAS) spectroscopy was employed to measure deuterium diffusion behavior in the Zr_2NiD_(4.8) phase. ^2H MAS NMR spectrum at ∼190 K provides with well-resolved 4 different site occupancies which can be assigned based on the crystal structure (16k (Zr_2Ni_2), 32m (Zr_3Ni), Zr_4 (16/ and 4b)). As the temperature rises, the ^2H peaks sensitively reflect the exchange behavior among the sites with evident change at around 230 K and reaching a uniform distribution of site occupancies, indistinguishable in NMR timescale, above 245 K. This behavior is reflected by the collapse of the ^2H MAS spectrum into a single peak. From analyses of VT MAS NMR spectra, we were able to extract multiple hopping rates and activation energies among face sharing interstices: for example, 32m ↔ 16/ hopping shows _(τc)=2.8×10^(-4)s at 245 K and E_a = 62.2 kJ/mol

Characterizing the ZrBe2Hx Phase Diagram via Neutron Scattering Methods

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Study of the magnetostructural transition in critical-element free Mn1−xNi1−xFe2xSi0.95Al0.05

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The crystal structure of LiMgAlD 6 from combined neutron and synchrotron X-ray powder diffraction

Abstract LiMgAlH 6 is the intermediate phase when LiMg(AlH 4 ) 3 is heated. It contains 9.4 wt.% hydrogen, of which 4.8 wt.% is released during the decomposition step to MgH 2 and LiH. Deuterated LiMgAlD 6 was prepared by heat-treating LiMg(AlD 4 ) 3 at 130 • C. Powder neutron and synchrotron X-ray diffraction patterns were measured and the structure was refined using the Rietveld technique on both patterns simultaneously. LiMgAlD 6 crystallizes in the trigonal space group P321 with a = 7.9856(4)Å and c = 4.3789(3)Å. The structure consists of isolated AlD 6 octahedra connected through octahedrally coordinated Mg-and Li-atoms

Exploring V-Fe-Co-Ni-Al and V-Fe-Co-Ni-Cu high entropy alloys for magnetocaloric applications

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