Dehydrogenation process and thermal stability of Mg-Ti-H films in-situ hydrogenated by microwave reactive plasma-assisted co-sputtering technique

Abstract In-situ hydrogenated Mg-Ti-H films with different Ti contents (0 ≤ at.% Ti ≤ 19.5) were deposited in a single-step process using the microwave reactive plasma-assisted co-sputtering technique. Multi-phase films containing tetragonal β–MgH 2 , metastable orthorhombic γ–MgH 2 and metastable hexagonal Mg-Ti were obtained depending on the Ti content. Subsequent to their deposition, the films underwent various thermal treatments aimed at studying their stability and sorption behavior. The structural and morphological properties were investigated by X-ray diffraction and scanning electron microscopy, before and after treatments. The thermal stability was studied by thermogravimetric and differential thermal analysis coupled with mass spectrometry. The results showed that the Mg-Ti phase remains structurally stable up to at least 500 °C after dehydrogenation, while the orthorhombic γ-MgH 2 phase no longer re-forms after its decomposition. A significant decrease of the Mg-Ti-H films desorption temperature compared to single phase MgH 2 and TiH 2 films was observed for the films with a Ti content in the 2.7–6.6 at.% Ti range.