Synthesis and decomposition mechanisms of ternary Mg(2)CoH(5) studied using in situ synchrotron X-ray diffraction

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  • M. Norek, Military University of Technology
  • ,
  • Thomas Kollin Nielsen
  • M. Polanski, Military University of Technology
  • ,
  • I. Kunce, Military University of Technology
  • ,
  • T. Płociński, Warsaw University of Technology
  • ,
  • L.R. Jaroszewicz, Military University of Technology
  • ,
  • Y. Cerenius, Lund University
  • ,
  • Torben René Jensen
  • J. Bystrzycki, Military University of Technology
A ternary MgCoH hydride was synthesized using a novel method that relies on a relatively short mechanical milling time (1 h) of a 2:1 MgH-Co powder mixture followed by sintering at a sufficiently high hydrogen pressure (>85 bar) and heating from RT to 500 °C. The ternary hydride forms in less than 2.5 h (including the milling time) with a yield of ∼90% at ∼300 °C. The mechanisms of formation and decomposition of ternary MgCoH were studied in detail using an in situ synchrotron radiation powder X-ray diffraction (SR-PXD). The obtained experimental results are supported by morphological and microstructural investigations performed using SEM and high-resolution STEM. Additionally, thermal effects occurring during the desorption reaction were studied using DSC. The morphology of as-prepared ternary MgCoH is characterized by the presence of porous particles with various shapes and sizes, which, in fact, are a type of nanocomposite consisting mainly of nanocrystallites with a size of ∼5 nm. MgCoH decomposes at approximately 300 °C to elemental Mg and Co. Additionally, at approximately 400 °C, MgCo is formed as precipitates inserted into the Mg-Co matrix. During the rehydrogenation of the decomposed residues, prior to the formation of MgCoH, MgH appears, which confirms its key role in the synthesis of the ternary MgCoH .
Original languageEnglish
JournalInternational Journal of Hydrogen Energy
Pages (from-to)10760-10770
Number of pages11
Publication statusPublished - 22 Jun 2011

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