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Abstract: By means of in situ synchrotron radiation powder X-ray diffraction, powder neutron diffraction, attenuated total reflectance infrared spectroscopy, differential scanning calorimetry and the Sieverts techniques we have investigated how anion substitution in the LiBH4–LiBr system leads to changes in the structural, physical, chemical and hydrogen storage properties of this material. Mechano-chemical treatment facilitates formation of a hexagonal solid solution h-Li(BH4)1−xBrx whereas heating at elevated temperatures, i.e. T > 112 °C appears to allow full solubility in the system LiBH4−LiBr. The first step in the anion substitution process may be dissolution of small amounts of LiBH4 in α-LiBr deduced from observation of a hexagonal solid solution with unit cell volume similar to β-LiBr for a hand-mixed sample. The solid solution, Li(BH4)1−xBrx, is isostructural to the hexagonal high temperature polymorph of LiBH4. This solid solution melts at a significantly higher temperature depending on the composition as compared to h-LiBH4. Furthermore, a new hexalithium borate tribromide, Li6(BO3)Br3 was discovered and structurally characterized. [Copyright &y& Elsevier]

Abstract: The hydrogenation behavior of 3CaH2+4MgB2+CaF2 composite was studied by manometric measurements, powder X-ray diffraction, differential scanning calorimetry and attenuated total reflection infrared spectroscopy. The maximum observed quantity of hydrogen loaded in the composite was 7.0wt%. X-ray diffraction showed the formation of Ca(BH4)2 and MgH2 after hydrogenation. The activation energy for the dehydrogenation reaction was evaluated by DSC measurements and turns out to be 162±15kJmol−1 H2. This value decreases due to cycling to 116±5kJmol−1 H2 for the third dehydrogenation step. A decrease of ca. 25–50°C in dehydrogenation temperature was observed with cycling. Due to its high capacity and reversibility, this composite is a promising candidate as a potential hydrogen storage material. [Copyright &y& Elsevier]