Abstract
The compound Mg2FeH6 was synthesized from a 2Mg-Fe mixture in a single process through high-energy ball milling under hydrogen atmosphere at room temperature. The complex hydride was prepared from Mg powder and granulated or powdered Fe using a planetary mill. The phase evolution during different milling times was performed by X-rays diffraction technique. The dehydrogenation behavior of the hydride was investigated through simultaneous thermal analyses of differential scanning calorimetry and thermogravimetry coupled with mass spectrometer. The use of powdered iron as starting material promoted conversion to complex hydride at shorter milling times than when granulated iron was used, nevertheless, after 24 hours of milling the 2Mg-Fe (powdered or granulated) mixtures presented similar dehydrogenation behavior. The hydrogen absorption during milling was on average 3.2 wt. (%), however, changing the proportions of the reagents to 3Mg-Fe a Mg2FeH6-MgH2 based nanocomposite with higher density of hydrogen (5.2 wt. (%)) was obtained.
Highlights
Magnesium is an attractive material to hydrogen storage due to several advantages, such as its abundance on theEarth’s crust, its low cost and the high hydrogen storage capacity of its hydride (7.6 wt. (%))
A processing route to reduce these severe conditions is the mechanical alloying of precursory materials before sintering[4], a direct synthesis of the hydride can be obtained when the milling is performed under a hydrogen pressure (Reactive Milling-RM)[5,6]
The γ-MgH2 phase formation synthesized at room temperature by ball milling was reported in others papers[19,21]
Summary
Magnesium is an attractive material to hydrogen storage due to several advantages, such as its abundance on the. Its main drawbacks are its high stability and slow hydrogen sorption kinetics In this context, the magnesium complex hydrides appear as an interesting alternative, compromising hydrogen storage capacity for better absorption – desorption kinetics. A processing route to reduce these severe conditions is the mechanical alloying of precursory materials before sintering[4], a direct synthesis of the hydride can be obtained when the milling is performed under a hydrogen pressure (Reactive Milling-RM)[5,6]. This mechanically activated method can reduce the grain and. In order to obtain a complete reaction of the metallic elements and a higher hydrogen gravimetric density, we performed the reactive milling of a 3Mg-Fe mixtures under hydrogen pressure
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