Structural Properties and Reversible Deuterium Loading of MgD2鈥揟iD2 Nanocomposites

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• 作者：Marine Ponthieu ; Fermin Cuevas ; Jose Francisco Fern谩ndez ; Laetitia Laversenne ; Florence Porcher ; Michel Latroche
• 刊名：Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：September 19, 2013
• 年：2013
• 卷：117
• 期：37
• 页码：18851-18862
• 全文大小：650K
• 年卷期：v.117,no.37(September 19, 2013)
• ISSN：1932-7455

文摘

Structural properties and reversible deuterium uptake of MgD₂鈥揟iD₂ nanocomposites have been studied by joint X-ray and neutron diffraction analyses to shed light on the extremely fast hydrogenation kinetics of these materials. (1 鈥?x)MgD₂鈥?i>xTiD₂ nanocomposites with compositions ranging between x = 0 and 0.5 have been prepared by reactive ball milling of Mg and Ti powders under deuterium pressure. They consist of mixtures of MgD₂ (尾-and 纬-polymorphs) and 蔚-TiD₂ phases homogenously distributed at the nanoscale with crystallite sizes below 15 nm. Minor phase miscibility is detected with Mg solubility in the TiD₂ phase up to 8 at.% and Ti solubility in the 尾-MgD₂ up to 7 at.% Ti. At moderate temperatures and pressures (T < 600 K, P_D2 < 1 MPa) reversible deuterium loading in MgD₂鈥揟iD₂ nanocomposites only occurs through the 尾-MgD₂ to Mg transformation. Mg/MgD₂ thermodynamics is not modified as 纬-MgD₂ and Ti solubility in 尾-MgD₂ are metastable and do not operate during reversible deuterium loading. However, the TiD₂ phase allows for outstanding D-sorption kinetics in the Mg/MgD₂ system. This paper demonstrates that TiD₂ inclusions limit the grain growth of Mg and MgD₂ phases allowing for short D-diffusion paths. Furthermore, we provide evidence that the TiD₂ phase also favors H-mobility through the existence of coherent coupling between TiD₂ and Mg/MgD₂ phases and the presence of sub-stoichiometric MgD_2-畏 and TiD_2-畏 phases.