353 research outputs found
Transparent yttrium hydride thin films prepared by reactive sputtering
Metal hydrides have earlier been suggested for utilization in solar cells.
With this as a motivation we have prepared thin films of yttrium hydride by
reactive magnetron sputter deposition. The resulting films are metallic for low
partial pressure of hydrogen during the deposition, and black or
yellow-transparent for higher partial pressure of hydrogen. Both metallic and
semiconducting transparent YHx films have been prepared directly in-situ
without the need of capping layers and post-deposition hydrogenation. Optically
the films are similar to what is found for YHx films prepared by other
techniques, but the crystal structure of the transparent films differ from the
well-known YH3 phase, as they have an fcc lattice instead of hcp
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
publishedVersio
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
Study of the magnetostructural transition in critical-element free Mn1−xNi1−xFe2xSi0.95Al0.05
publishedVersio
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