Kinetics of deuteration of the Pd0.772Ag0.228 alloy with α/β phase transition by in-situ neutron diffraction

JOURNAL OF ALLOYS AND COMPOUNDS

卷:790

Article

Catti, Michele¹  Fabelo, Oscar²  Filabozzi, Alessandra³  Pietropaolo, Antonino⁴  Santucci, Alessia⁴  Tosti, Silvano⁴ 

[1] Univ Milano Bicocca, Dipartimento Sci Mat, Via Cozzi 55, I-20125 Milan, Italy

[2] Inst Laue Langevin, 71 Ave Martyrs, F-38000 Grenoble, France

[3] Univ Roma Tor Vergata, Dipartimento Fis, Via Ric Sci 1, I-00133 Rome, Italy

[4] ENEA, Dipartimento Fus & Tecnol Sicurezza Nucl, Via Fermi 45, I-00044 Frascati, Italy

关键词: Hydrogen/deuterium absorption;    Palladium-silver alloy;    Neutron diffraction;    Kinetic mechanisms;   

DOI  :  10.1016/j.jallcom.2019.03.216

来源: Elsevier

【 摘 要 】

The deuteration reaction of a Pd0.772Ag0.228 foil was studied by neutron powder diffraction measurements vs. time in different T and p(D-2) conditions (D20 and D2B high-resolution diffractometers at ILL, France). The system has great importance as permeable membrane for hydrogen separation. At p = 1 bar and T < 200 degrees C Bragg peak splitting indicates the presence of two cubic phases, to be identified with the a and beta modifications of palladium hydride. Rietveld refinements provided the corresponding a(alpha), and a(beta) lattice constants, the nu(alpha), and nu(beta) occupancies of D, and the beta phase volume fraction vs. time during deuteration progress. A continuous alpha -> beta transformation takes place till reaction end. At T= 200 degrees C or p> 1 bar a single phase was always observed. The phase diagram of Pd0.772Ag0.228D nu is thus shown to present a alpha+beta two-phase domain less extended but similar to that of PdH nu, at variance with most thermodynamic measurements suggesting full single-phase behavior. The p(t) kinetic data of deuteration at 80 degrees C/1 bar can be interpreted by a mechanism based on a first-order nucleation step followed by a zero-order step of surface adsorption and dissociation of the D-2 molecule. (C) 2019 Elsevier B.V. All rights reserved.

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