Thermal Stability of Hydrogenated Mg/Al Thin Films.

Magnesium alanate Mg(AlH4)2 is one promising material for H2 storage because it has 9.3 wt % H2 storage capacity and decomposition temperature close to 160 °C. In this paper we present a study on the structural characterization and thermal stability of Mg alanate thin films. Samples in form of Mg/Al multilayer thin films prepared by electron beam deposition and then submitted to thermal annealing in UHV conditions to promote the atomic mixing and stimulate the formation of Mg-Al phases. Annealed samples were then coated by a thin Pd capping layer to catalyse the D2 adsorption during thermal treatment at 150 °C in D2 atmosphere. The structural characterization of the thin film samples was carried out by XRD and the thermal stability of the deuterated samples was studied by Thermal Desorption Spectroscopy (TDS). The TDS spectra show a maximum of the D2 effusion rate at T ∼ 200 °C which is attributed to the deuterium desorption from the Mg alanate. Analysis of the effusion kinetics indicates that the D2 effusion is controlled by the decomposition of the Mg alanate and presents an effective activation energy value of 1.33 ± 0.02 eV. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]