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Copyright of Materials Science / Medziagotyra is the property of Kaunas University of Technology, represented by Prof. Rymantas Jonas Kazys and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The hydrogen sorption kinetics of MgH 2 ‒VO 2 (B) composites synthesised by mechanical milling have been studied. The microstructural properties of composites were characterized by means of X-ray diffraction (XRD), Raman spectroscopy, Scanning electron microscopy (SEM), Particle size analysis (PSD), while sorption behaviour was followed by differential scanning calorimetry (DSC) and Sievert measurements. Results have shown that although desorption temperature reduction is moderate; there is a substantial improvement in hydrogen sorption kinetics. The complete desorption of pure MgH 2 at elevated temperature takes place in more than 30 min while the composite fully desorbs in less than 2 min even at lower temperatures. It has been shown that the metastable γ–MgH 2 phase and the point defects have a decisive role in desorption process only in the first sorption cycle, while the second and the subsequent sorption cycles are affected by microstructural and morphological characteristics of the composite. [ABSTRACT FROM AUTHOR]

Abstract: The hydrogen desorption properties of MgH2–LiAlH4 composites obtained by mechanical milling for different milling times have been investigated by Thermal Desorption Spectroscopy (TDS) and correlated to the sample microstructure and morphology analysed by X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The MgH2–LiAlH4 composites show improved hydrogen desorption properties in comparison with both as-received and ball-milled MgH2. Mixing of MgH2 with small amount of LiAlH4 (5 wt.%) using short mechanical milling (15 min) shifts, in fact, the hydrogen desorption peak to lower temperature than those observed with both as-received and milled MgH2 samples. Longer mixing times of the MgH2–LiAlH4 composites (30 and 60 min) reduce the catalytic activity of the LiAlH4 additive as revealed by the shift of the hydrogen desorption peak to higher temperatures. [Copyright &y& Elsevier]

Abstract: The hydrogen desorption (HD) properties of MgH2-CeO2 composite prepared by mechanically milling of MgH2 and cubic CeO2nano have been examined. Morphology and microstructure of composites have been studied by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), laser scattering analysis and correlated with desorption properties obtained by means of temperature programmed desorption (TPD). It has been shown that decrease of crystallite and particle size of the samples lead to significant lowering of desorption temperature. Further, the activation energy for desorption has been calculated using Kissinger equation. Obtained value of 60±10kJ/mol indicates that the activation energy of hydrogen desorption is sufficiently decreased by the catalytic effect of vacant CeO2 structure. Consequently the surface activation of sample plays a major role in HD reaction. [Copyright &y& Elsevier]