Hydrogen sorption kinetics of titanium hydride thin filmsTuesday (27.09.2016) 17:48 - 17:51 Part of:
Titanium hydride (TiH2) has been studied in the last years in a variety of different fields. Because of its impressive hydrogenation kinetics it has its importance in the field of hydrogen storage. Additionally, transition metals are known to improve hydrogen storage materials and act as catalysts in the sorption process. Despite the low weight percentage of hydrogen, TiH2 can take (4%), it is a material in which H diffuses very easily and furthermore it is stable in air and can protect other metal hydride from oxidation. Because of its high stability, the desorption kinetics are very slow.
In this work, we focus on the hydrogen sorption behavior in thin films of 50-800nm thickness under different conditions and compare it to bulk material. To estimate the influences of the surface on the sorption behavior, samples with and without Palladium (Pd) were compared. Pure ?-Ti and Pd/Ti bilayers were deposited by ion beam sputtering on Si substrates. This technique leads to small grain size which improves the diffusion. Hydrogenation was studied at different temperatures (RT to 300°C) and for different duration times (1 to 600min) at 1 to 10 bars of H atmosphere in order to measure the kinetic barriers at the interfaces and the diffusion coefficients. Hydrogen sorption and diffusion coefficients were quantified by X-ray Diffraction. TEM was used for microstructural analyses and surface was studied by SEM/FIB. Full ?-TiH2 hydrogenation appears in the XRD characterization for samples hydrogenated over 80min at 300°C and 10bars of H. Possible reversibility of ?-TiH2 to ?-Ti was studies on magnesium oxide sputtered layer to avoid the formation of Silicates at higher temperatures.