Sorption properties of NaBH(4)/MH(2) (M = Mg, Ti) powder systems
Garroni, S × Milanese, C Girella, A Marini, A Mulas, G Menéndez Dalmau, Enric Pistidda, C Dornheim, M Suriñach, S Baró, M D #
International Journal of Hydrogen Energy vol:35 issue:11 pages:5434-5441
The sorption properties of NaBH4/MH2 (M = Mg, Ti) powder systems prepared by high-energy ball milling have been thoroughly investigated. Concerning the systems containing MgH2, the 2:1 and 1:2 molar compositions have been studied and both lead to a multistep desorption pathway, where the formation of MgB2 confirms the destabilization of NaBH4 induced by the presence of MgH2. A noticeable kinetic enhancement is achieved for the MgH2-rich system (composition 1:2) if compared with the NaBH4-rich system (composition 2:1). Even though full re-absorption is obtained for neither of the two compositions, fast kinetics is achieved. During absorption, the unsuspected formation of the perovskite-type hydride NaMgH3 is detected and it is showed that this ternary phase contributes to reduce the gravimetric capacity of the systems. Conversely, in the 2NaBH4/ TiH2 system, there is no formation of the intermetallic compound TiB2. Furthermore, a decrease in the sorption kinetics is found in comparison with the systems based on MgH2.