Hydriding/dehydriding behavior of Mg2CoH5 produced by reactive mechanical milling
Hydriding/dehydriding behavior of Mg2CoH5 produced by reactive mechanical milling
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DOI：
10.1016/j.jallcom.2007.09.102
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发表时间：
2008-09
影响因子：
6.2
通讯作者：
I. G. Fernández;G. Meyer;F. Gennari
中科院分区：
文献类型：
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作者：
I. G. Fernández;G. Meyer;F. Gennari
将2 mg-Co混合物在氩气中球磨，然后在氢气中进行反应机械合金化(RMA)，这两种工艺都是在室温下进行的，从而得到了复合镁钴氢化合物。在RMA过程中，在较短的球磨时间(10h)下生成了MgH_2，90h后生成了Mg_2CoH_5(50wt%)。成品率和形成时间的提高可能与球磨前组织的细化和镁钴混合的加强有关。差示扫描量热法(DSC)研究表明，RMA生成的Mg2CoH5相的起始分解温度约为205℃，并测定了静态(300℃)和动态(230-330℃)条件下的吸附和脱附PCI。观察到一个重要的滞后和两个平台，并与高压平台和低压平台氢化物的形成/分解相关联。为了比较吸氢动力学，还采用烧结法在410℃和6.0 Mpa的氢气压力下得到了质量分数为65wt%的Mg2CoH5。在150-350℃的温度范围内吸收非常快，与合成过程无关。然而，RMA粉末的脱附曲线显示出更好的行为。在特定的热处理条件下，Mg2CoH5分解后观察到了MgCo相，而没有检测到MgCo2相。这一研究结果进一步证实了与原子迁移率有关的动力学因素在镁钴金属间化合物形成中起关键作用的观点。
Complex Mg2CoH5hydride was obtained by a combined procedure that included a milling stage of a 2Mg–Co mixture under argon followed by reactive mechanical alloying (RMA) under hydrogen, both at room temperature. During RMA, MgH2is produced at short milling times (10h) and Mg2CoH5(50wt%) after 90h. Improvement in the yield and the formation times could be associated with both refinement of microstructure and enhancement of intermixing of Mg–Co during pre-milling stage. DSC studies of Mg2CoH5phase produced by RMA show that the starting decomposition temperature is about 205°C. Absorption and desorption PCIs were determined under static (300°C) and dynamic (230–330°C) conditions. An important hysteresis and two plateaus were observed and correlated with formation/decomposition of Mg2CoH5(high-pressure plateau) and Mg6Co2H11(low-pressure plateau) hydrides. For comparing hydrogen sorption kinetics, Mg2CoH5(65wt%) was also obtained by a sintering method at 410°C and 6.0MPa of hydrogen pressure. Absorption was very fast in the temperature range of 150–350°C, independently of synthesis procedure. However, desorption curves showed a better behavior for RMA powders. MgCo was observed after decomposition of Mg2CoH5under particular thermal treatments, while MgCo2phase was not detected. The results of this study reinforce the idea that kinetics factors related with atomic mobility play a key role in the formation of Mg–Co intermetallics.