Deuterium Distribution in Fe/V Multi-Layered Films

The recent progress of Atom Probe Tomography (APT) has opened up atomic-scale elemental analysis including hydrogen species. For APT measurements, the use of deuterium is highly recommended, due to its low mobility compared to the fast and quantum mechanically tunneling isotope hydrogen. In addition, deuterium can be distinguished from hydrogen originating from the APT analysis chamber. To date, however, APT studies on materials with high D concentrations are scarce. In this study, the D concentration profile in a Fe/V multi-layered film sample was investigated, and spanned a wide concentration range. The mean hydrogen isotope concentration was alternatively quantified by electromotive force (EMF) measurements on a similar Fe/V film, thus verifying the APT results. The reduction found in the D concentration at the Fe/V interface results from local alloying at the Fe/V interfaces which accompanies a change in the available volume in the V lattice. Even at the same Fe concentration, the shape of the observed D depth profile was asymmetric at high D$_2$ pressures. This indicates a stress impact caused by the deposition sequence

The impact of nanoscale compositional variation on the properties of amorphous alloys

The atomic distribution in amorphous FeZr alloys is found to be close to random, nevertheless, the composition can not be viewed as being homogenous at the nm-scale. The spatial variation of the local composition is identified as the root of the unusual magnetic properties in amorphous Fe$_{Zahl}$1-xZr$_{x}$ alloys. The findings are discussed and generalised with respect to the physical properties of amorphous and crystalline materials

Wasserstoff in V-Fe dünnen Schichten und V-Fe/Fe mehrfachschchten

In dieser Arbeit Wasserstoff induzierte zweiachsige Spannung und lokale Verteilung von Wasserstoff in V-Fe-Filme und V-Fe/Fe-mehrfachschichtigen Filme wurden untersucht. Der Spannung Entwicklung und Relaxationsverhalten in den Filmen wurden durch Kombination von in-situ Spannung, in-situ Schallemission und in-situ XRD-Messungen interpretiert. Die Spannung Entwicklung von V-Fe dünnen Schichten dünner als 100 nm zeigte bemerkenswerte Korrelation mit Defekt-H-Wechselwirkung bei sehr niedrigen Konzentrationen. Mit zunehmender H-Konzentration, intermittierende Spannungsrelaxation aufgrund Wiederherstellung der intrinsischen Versetzungen festgestellt wurde, bis der Film entspannt auf der Stufe der Hydridbildung. Die V-Fe/Fe mehrfachschichtige Filme zeigte riesigen Zugspannung auf Wasserstoff geladen, die durch bevorzugte Ort Besetzung von Wasserstoff in das Gitter betrachtet wurde. Atomsondentomographie Analyse erfolgreich zeigte Deuterium Verteilung in den Filmen auf atomarer Skala. Bestimmung des richtigen D-Konzentration und die drei-dimensionale Verteilung wurden über neu gestaltete Methode unter Beweis gestellt. Lokale Anreicherung von D-Atomen an der Grenzfläche zwischen Film und Substrat wurde als Ergebnis der D-Trapping auf Versetzungen beobachtet. Die Analyse der mehrfachschichtigen Filmen ergab jedoch, Deuterium verarmten Region von 0,4 bis 1,0 nm bei V-Fe/Fe Grenzfläche

Role of atomic hydrogen supply on the onset of CO2_2 methanation over La–Ni based hydrogen storage alloys studied by in-situ approach

Mechanochemical CO$_{2}$ methanation reactions using LaNi$_{5}$ and LaNi$_{4.6}$Al$_{0.4}$ hydrogen storage alloy powders were investigated by the in-situ monitoring of the gas pressure change during ball-milling. Methane generation begins when the H$_{2}$ partial pressure drops due to the H-uptake by the powder. Phase transition occurred in the sample after milling for 15 min and 224 min, with separate metallic Ni, La-oxide and La-hydroxide phases observed. Methane generation continued even after this phase separation. Our results imply that the formation of La-hydroxide at the surface and sub-surface contributed to methane generation during ball-milling. A comparison of LaNi$_{5}$ and LaNi$_{4.6}$Al$_{0.4}$ suggests the amount of hydrogen stored in the hydrogen storage powder dominates the timing of the onset of the methane generation

The impact of nanoscale compositional variation on the properties of amorphous alloys

The atomic distribution in amorphous FeZr alloys is found to be close to random, nevertheless, the composition can not be viewed as being homogenous at the nm-scale. The spatial variation of the local composition is identified as the root of the unusual magnetic properties in amorphous Fe1-xZrx alloys. The findings are discussed and generalised with respect to the physical properties of amorphous and crystalline materials