Hydrogen uptake kinetics of Pd coated FeTi films
| Autor: | D.O. Boerma, E.M.B. Heller, A.M. Vredenberg |
|---|---|
| Rok vydání: | 2006 |
| Předmět: |
Materials science
Hydrogen Annealing (metallurgy) Kinetics Analytical chemistry Oxide General Physics and Astronomy chemistry.chemical_element Surfaces and Interfaces General Chemistry Rate equation Condensed Matter Physics Surfaces Coatings and Films chemistry.chemical_compound Hydrogen storage chemistry FETI Thin film |
| Zdroj: | Applied Surface Science. 253:771-777 |
| ISSN: | 0169-4332 |
| Popis: | The kinetics of hydrogen uptake of thin films of FeTi deposited on Si substrates and covered with 20 nm Pd were studied. The films serve as a model system for powdered FeTi, with grains that are (partly) covered with Pd, which serves as a protection for severe oxidation. Two FeTi compositions near the 50/50 composition were studied. The hydrogen uptake kinetics as a function of temperature and pressure were measured by probing the differential pressure between a small hydriding reaction chamber and a reference chamber. Both compositions showed first order kinetics for the largest portion of the uptake. Using results of additional measurements in which the thickness of the layers was varied, a model is proposed in which the uptake proceeds via fast channels through the film, followed by slower diffusion into the bulk. Finally, the influence of oxidation was studied. An FeTi-oxide underneath the Pd layer is a barrier for H diffusion. It was found that by annealing the H uptake rate could be increased. This is probably due to the decomposition of the oxide. Samples partly covered with Pd and partly by FeTi-oxides, obtained by decomposing the fully covered structure by air annealing at 250 °C, showed uptake throughout the entire FeTi film with an even faster rate than in a fully covered film. Some explanation with simple models of the observed phenomena is given. |
| Databáze: | OpenAIRE |
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