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Synthesis and decomposition mechanisms of ternary Mg2COH5 studied using in situ synchrotron X-ray diffraction

In English

Författare

  • M. Norek
  • T. K. Nielsen
  • M. Polanski
  • I. Kunce
  • T. Plocinski
  • L. R. Jaroszewicz
  • Yngve Cerenius
  • T. R. Jensen
  • J. Bystrzycki

Summary, in English

A ternary Mg2COH5 hydride was synthesized using a novel method that relies on a relatively short mechanical milling time (1 h) of a 2:1 MgH2-Co powder mixture followed by sintering at a sufficiently high hydrogen pressure (>85 bar) and heating from RT to 500 degrees C. The ternary hydride forms in less than 2.5 h (including the milling time) with a yield of similar to 90% at similar to 300 degrees C. The mechanisms of formation and decomposition of ternary Mg2COH5 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 Mg2COH5 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 similar to 5 nm. Mg2COH5 decomposes at approximately 300 degrees C to elemental Mg and Co. Additionally, at approximately 400 degrees C, MgCo is formed as precipitates inserted into the Mg Co matrix. During the rehydrogenation of the decomposed residues, prior to the formation of Mg2COH5, MgH2 appears, which confirms its key role in the synthesis of the ternary Mg2COH5. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Publiceringsår

2011

Språk

Engelska

Sidor

10760-10770

Publikation/Tidskrift/Serie

International Journal of Hydrogen Energy

Volym

36

Issue

17

Dokumenttyp

Artikel i tidskrift

Förlag

Elsevier

Ämne

  • Natural Sciences
  • Physical Sciences

Nyckelord

  • Magnesium-cobalt hydride
  • Synthesis
  • Mechanical milling
  • In situ
  • SR-PXD
  • Microstructure

Status

Published

ISBN/ISSN/Övrigt

  • ISSN: 1879-3487