Phase Stabilities in the Mg鈥揝i鈥揌 System Tuned by Mechanochemistry

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• 作者：Junxian Zhang ; Zhinian Li ; Fermin Cuevas ; Michel Latroche
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：September 25, 2014
• 年：2014
• 卷：118
• 期：38
• 页码：21889-21895
• 全文大小：380K
• ISSN：1932-7455

文摘

Reversible hydrogen storage in the Mg鈥揝i鈥揌 system has been studied through mechanochemistry using 2Mg + Si powders as reactants under a hydrogen pressure of 9 MPa. Depending on the milling energy, the equilibrium state of this system can be tuned: either Mg₂Si or 2MgH₂ + Si is formed as a stable phase at high and low rotation speeds, respectively. This result is reasonably explained by the change of local temperature at the collision impact with milling speed. Therefore, we here demonstrate that reversibility in the Mg鈥揝i鈥揌 system is feasible following the reaction Mg₂Si + 2H₂ 鈫?2MgH₂ + Si. Indeed, the direct reaction could be fully attained by milling Mg₂Si at a low rotation speed. The reverse reaction could also be triggered by milling at a high rotation speed but only when some amount of Mg₂Si is used to catalyze the reaction between magnesium hydride and silicon.