Effect of the Partial Replacement of CaH₂ with CaF₂ in the Mixed System CaH₂ + MgB₂

Abstract

In this work the effect of a partial replacement of CaH2 with CaF2 on the sorption properties of the system CaH2 + MgB2 has been studied. The first five hydrogen absorption and four desorption reactions of the CaH2 + MgB2 and 3CaH2 + CaF2 + 4MgB2 systems were investigated by means of volumetric measurements, high-pressure differential scanning calorimetric technique (HP-DSC), 11B and 19F MAS NMR spectroscopy, and in situ synchrotron radiation powder X-ray diffraction (SR-PXD). It was observed that already during the mixing of the reactants formation of a nonstoichiometric CaF2–xHx solid solution takes place. Formation of the CaF2–xHx solid solution sensibly affects the overall hydrogen sorption reactions of the system CaH2 + MgB2.