1. Controlled mechanochemical synthesis and hydrogen desorption mechanisms of nanostructured Mg2CoH5.
- Author
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Zepon, G., Leiva, D.R., Kaufman, M.J., Figueroa, S.J.A., Floriano, R., Lamas, D.G., Asselli, A.A.C., and Botta, W.J.
- Subjects
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MECHANICAL chemistry , *NANOSTRUCTURED materials , *MAGNESIUM compounds , *HYDROGEN absorption & adsorption , *HYDROGEN storage , *LOW temperatures - Abstract
Magnesium complex hydrides are attractive for hydrogen storage applications, mainly due to their high volumetric capacities and to their relatively low cost. In this work, nanocrystalline Mg 2 CoH 5 was synthesized with very high yields (97%) by reactive milling cobalt and magnesium under relatively mild processing conditions (30 bar of H 2 pressure and 12 h of milling). The behavior of the milled Mg 2 CoH 5 during heating was studied by a combination of several techniques including DSC, QMS, TGA and in-situ synchrotron XRD. It is shown for the first time that two different mechanisms of hydrogen desorption take place. At low temperatures (up to 325 °C), some hydrogen is released by a diffusional mechanism with no change in the crystalline structure of the high temperature γ-Mg 2 CoH 5 phase. At higher temperatures, above 325 °C, the γ-Mg 2 CoH 5 phase becomes unstable and the complex hydride decomposes into Mg, Co and H 2 . This is the first work to report the diffusional hydrogen desorption mechanism for the Mg 2 CoH 5 or any other complex hydride. Furthermore, a complete description of the allotropic β-Mg 2 CoH 5 to γ-Mg 2 CoH 5 phase transition is provided. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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