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Growth Mechanism for the Controlled Synthesis of MgH2/Mg Crystals via a Vapor-Solid Process

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タイトル: Growth Mechanism for the Controlled Synthesis of MgH2/Mg Crystals via a Vapor-Solid Process
著者: Zhu, Chunyu 著作を一覧する
Hosokai, Sou 著作を一覧する
Akiyama, Tomohiro 著作を一覧する
キーワード: Hydrogen storage
magnesium hydride
crystal growth
hydriding chemical vapor deposition
発行日: 2011年 9月 7日
出版者: American Chemical Society
誌名: Crystal Growth & Design
巻: 11
号: 9
開始ページ: 4166
終了ページ: 4174
出版社 DOI: 10.1021/cg200733b
抄録: In this paper, we continue the work on the controlled growth of MgH2/Mg nano/microstructures, in which we highlight the growth mechanism from thermodynamics and kinetics, by a catalyst-free vapor-solid method of hydriding chemical vapor deposition (HCVD) which is a process of the evaporation-condensation of Mg under high-pressure H2. We easily achieved control of both the morphology and composition, including nano/microsized powders of MgH2 or a mixture of MgH2 and Mg, nanosized straight and curved MgH2 fibers, irregular bulk microstructures of Mg, hexagonal microplates of Mg, and microdendritic Mg, of the products by adjusting three experimental parameters: evaporation temperature, deposition temperature, and H2 pressure. The products were compositionally separated into three categories, Mg, MgH2, and a mixture of both, based on the growth temperature within the thermodynamic P-T diagram of the Mg-H system. A growth mechanism for the HCVD process was proposed from the perspectives of thermodynamics and kinetics, comprising a two-step reaction sequence on the deposition substrate of the first Mg condensation, Mg(g) → Mg(s), with subsequent hydrogenation, Mg(s) + H2(g) ↔ MgH2(s). The composition of the products was controlled by controlling the reaction rates of these two steps, in which these reaction rates were determined by the  atmospheric conditions of deposition temperature, H2 pressure and evaporation temperature. These Mg/MgH2 nano/microstructures may find applications in hydrogen storage and batteries. By choosing suitable experimental parameters, such as evaporation temperature, deposition temperature, and H2 pressure, this simple vapor-solid method may be extended to the synthesis of nano/microstructures of other metal hydrides.
Rights: Reprinted (adapted) with permission from Crystal Growth and Design. Copyright 2011 American Chemical Society.
資料タイプ: article (author version)
出現コレクション:雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

提供者: 朱 春宇


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