Hydrogen Sorption in the LiH–LiF–MgB2 System


A composite material in the LiH–LiF–MgB2 system has been synthesized by high-energy ball milling. Some peaks in addition to that of the binary 2LiH–MgB2 and 2LiF–MgB2 systems are observed for the composite material by high-pressure differential scanning calorimetry (HP-DSC), indicating the formation of intermediate phases. In situ synchrotron radiation powder X-ray diffraction (SR-PXD) performed at 60 bar of H2 and 390 °C shows a superposition of both reaction pathways that are typical for 2LiH–MgB2 and 2LiF–MgB2. After hydrogen absorption of the LiH–LiF–MgB2 composite the vibrational modes of LiBH4 were observed by attenuated total reflection infrared (ATR-IR) spectroscopy. The 19F MAS NMR spectrum of the LiF–LiBH4 sample after heat treatment in hydrogen is strongly dominated by the centerband and spinning sidebands from LiF; in addition, a low-intensity resonance, very similar to that of [BF4] – ion, is identified.
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