XAS STUDY OF RNi2 HYDRIDES
Résumé
RNi2 Laves phases compounds (R = La, Ce) exist with a stoechiometry deviation (5% for CeNi2 and 10% for LaNi2) which leads to a structural disorder clearly observed by EXAFS at the Ni K-edge. These compounds easily absorb hydrogen up to 4.2 H/mole at room temperature. X-ray diffraction indicates that they are amorphous for hydrogen contents greater than 3.5 H/mole. EXAFS study at the Ni-K edge gives evidence of the increase of the local disorder upon hydrogenation. In addition a change of cerium valency induced by hydrogen absorption in CeNi2 was observed by a Ce LIII edge study.
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