Publications by authors named "R J Westerwaal"

Magnesium-based transition-metal hydrides are attractive hydrogen energy materials because of their relatively high gravimetric and volumetric hydrogen storage capacities combined with low material costs. However, most of them are too stable to release the hydrogen under moderate conditions. Here we synthesize the hydride of MgFeSi, which consists of MgFeH and MgSi with the same cubic structure.

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Article Synopsis
  • - The study shows that adding a thin PTFE coating onto Pd alloy thin films boosts their catalytic abilities for hydrogen-related applications.
  • - This enhancement leads to better hydrogen adsorption and desorption in sensors and storage materials that use Pd catalysts.
  • - The improved performance comes from chemical changes on the catalyst's surface caused by the PTFE, which alters how intermediate species bind during the hydrogen absorption process.
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We report for the first time on the experimental response of a Surface Plasmon Resonance fiber optic sensor based on wavelength modulation for hydrogen sensing. This approach of measuring the hydrogen concentration makes the sensor insensitive to intensity fluctuations. The intrinsic fiber sensor developed provides remote sensing and enables the possibility of multi-points sensing.

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For the daily use of hydrogen storage materials, not only their intrinsic storage properties are important, but also equally important is the performance under practical conditions. Besides the techniques already available for the fundamental characterization of storage materials, there is a growing need to test storage materials under conditions resembling day-to-day use. For that we developed and tested a downscaled hydrogen storage reactor with which it is possible to monitor the hydrogenation behavior under nonideal conditions.

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In addition to a mirrorlike (Mg2Ni) and a transparent (Mg2NiH4) state, thin films of Mg2NiHx exhibit a remarkable black state with low reflection over the entire visible spectrum, essentially zero transmission and a low electrical resistivity. Such a black state is not explicable for a homogeneous layer since a large absorption coefficient always yields substantial reflection. We show that it results from a self-organized and reversible double layering of metallic Mg2NiH0.

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