Interaction of oxide ceramics with metal hydrides

Abstract

Magnesium hydride (MgH2 ) is one of the most favorable hydrogen storage materials because it is directly formed from the reaction of Mg metal with gaseous hydrogen while reaching a high mass capacity (7.6 wt %). However, the sorption reaction is too slow for practical use and needs higher temperature than 300 °C for hydrogen sorption reactions. The hydrogen storage properties can be tailored by addition of small amount of transition metal oxides (TiO2,VO2 ). In order to understand the processes that occurred during sorption reaction we have used both theoretical and experimental approach to study reaction mechanism in powder and thin films materials. Processes taking place during hydrogen desorption from Mg/MgH2 thin films upon modification either by TiO2 capped layer or by ion irradiation were also investigated. Irradiation was used to produce controlled point defects quantity with well-defined depth distribution. It was shown that the size, shape, and concentration of Mg nuclei formed during hydrogen desorption from MgH2 thin films depend on the characteristics and distribution of the induced defects. Addition of VO2 to powder milling bland dramatically improves the kinetics of sorption reaction, It is worth to notice that the full charge/discharge is achieved at relatively low temperatures.