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MgH2 based composites with LiAlH4 and LiNH2 complex hydrides

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The investigation of materials that could match the requirements for hydrogen storage system to be used in automobile applications has been mostly focused on complex hydrides in the past few years. Especially, since the work of Chen et al. [1], Luo [2] and Vajo et al. [3] on mixtures of LiNH2/LiH, LiNH2/MgH2 and LiBH4/MgH2, there have been many publications dedicated to complex hydrides that are thermodynamically destabilized by ball milling with other hydrides [4÷7]. The advantage of such reactions is that the relatively large enthalpies of complex hydrides can be decreased by providing an alternate reaction pathway that liberates hydrogen. It has also been observed that new phases could be formed during the high-energy ball milling of different ratios of known hydrides [2, 3]. Very recently, it has been shown [4, 5] that the hydrogen desorption temperature of the composite constituent with the higher desorption temperature in the systems, substantially decreases linearly with increasing volume fraction of the constituent having lower desorption temperature. In the present work the composite approach is applied to the MgH2 + LiAlH4 and MgH2 + LiNH2 systems. The composites with various volume fractions of both constituents were processed by controlled mechanical milling (CMM) in a magneto-mill (under protective argon atmosphere). Hydrogen desorption was tested using a Differential Scanning Calorimeter (DSC) analysis. The aim of this work is to analyze the influence of intermetallic additives on magnesium hydrogen decomposition process in LiAlH4 and LiNH2 composites. experimental As-received commercial MgH2 powder (Sigma-Aldrich; ~98 wt. % purity; the rema[...]

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