SONG, Myoung-Youp; FOURNÈS, Léopold; DARRIET, Bernard

doi:10.1016/S0360-3199(02)00153-2

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SONG, Myoung-Youp
Division of Advanced Materials Engineering, Research Center of Advanced Materials Development

FOURNÈS, Léopold
Institut de Chimie de la Matière Condensée de Bordeaux [ICMCB]

DARRIET, Bernard
Institut de Chimie de la Matière Condensée de Bordeaux [ICMCB]

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International Journal of Hydrogen Energy. 2003, vol. 28, n° 8, p. 809-814

Elsevier

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After preparing Mg2Ni1−xFex (x=0.005, 0.01, 0.02 and 0.08) alloys, they were studied by Mössbauer resonance. The Mössbauer spectra of x=0.005 and 0.01 alloys exhibit two doublets (doublet 1, 2). That of x=0.02 alloys shows two doublets (doublet 1, 2) and one sextuplet, and that of x=0.08 alloy has only one sextuplet. Doublet 1 for x=0.005, 0.01 and 0.02 alloys is considered to result from a fraction of Fe in excess showing a superparamagnetic behavior. Doublet 2 is considered to result from the Fe substituted for Ni in the Mg2Ni phase. The values of isomer shift 0.25–0.29 mm/s suggest that the iron exists in the state Fe+3. The result that the quadrupolar splitting of doublet 2 is not zero shows that the distribution of electrons around the iron is asymmetric. Their values for the doublet 2, 1.21–1.39 mm/s, approach the value of quadrupolar splitting for the oxidation number +3. The sextuplet showing the magnetic hyperfine interactions results from the iron, which has not substituted the nickel in the Mg2Ni phase. The Mössbauer spectrum of the x=0.01 alloy hydrided at 723 K shows one doublet and sextuplet. The segregation of Fe is considered to result from the reaction of the Mg2Ni phase with the oxygen contained in the hydrogen as impurity...< Réduire

Mots clés en anglais

Mg2Ni1−xFex

Mössbauer resonance

Fe+3

Asymmetric distribution of electrons

Segregation of iron

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Study of Mg2Ni1−xFex alloys by Mössbauer resonance

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