Mechanical alloying and electronic simulations of 2Mg-Fe mixture powders for hydrogen storage
Mechanical alloying and electronic simulations of 2Mg-Fe mixture powders for hydrogen storage
复制标题
DOI：
10.1016/j.msea.2006.04.074
复制
发表时间：
2006-07
期刊：
影响因子：
6.4
通讯作者：
Dianwu Zhou;Songru Li;R. Varin;P. Peng;Jie Liu;F. Yang
中科院分区：
文献类型：
--
作者：
Dianwu Zhou;Songru Li;R. Varin;P. Peng;Jie Liu;F. Yang
2将Mg-Fe粉末混合物在氢气气氛下球磨，制备储氢材料。研究了球磨体系的微观结构和结晶性能。用第一性原理平面波赝势方法研究了氢化物相的能量和电子结构，解释了XRD、DSC和TGA分析的实验结果。通过计算MgH 2、（MgFe）H2固溶体和Mg 2FeH 6化合物的生成热，认为Mg 2FeH 6的形成过程为：Mg先固溶于部分H原子中形成MgH 2，然后Fe原子逐渐固溶于MgH 2晶格中形成（MgFe）H2固溶体，最后（MgFe）H2固溶体转变为Mg 2FeH 6相。不同球磨时间的粉末的DSC曲线均未发现分解温度的剧烈变化，这种相对缓慢的变化可以用Mg_2FeH_6形成过程的观点来解释。由于MgH 2相在两种β-MgH 2和Mg 2FeH 6共存的混合物中仍是主要相，Mg 2FeH 6相较MgH 2降低了混合物的负生成热，表明Mg_2FeH_6通过催化作用降低了MgH_2的脱附温度，Mg_2FeH_6的脱附速率最快。
2Mg–Fe powder mixture was milled in hydrogen atmosphere to prepare materials for hydrogen storage. The microstructure and dehydrogenating property of the milled system were examined. Then energy and electronic structure of the hydride phase were investigated by using a first-principles plane-wave pseudopotential method to explain the experimental results from XRD, DSC and TGA analysis. By calculating the heats of formation of MgH2, (MgFe)H2solid solutions and Mg2FeH6compound, the forming process of Mg2FeH6was assumed as that magnesium was first dissolved in some H atoms to form MgH2, second, iron atom progressively dissolved into MgH2lattice to form (MgFe)H2solid solutions, finally the (MgFe)H2solid solution can be changed into Mg2FeH6phase. For DSC curves as a function of temperature for all the powders milled for different time, a drastic change of dissociation temperature is never found, this kind of relatively sluggish change can be explained using the idea on forming process of Mg2FeH6. Since MgH2phase is still the major phase in the coexistence mixtures of two types of hydrides β-MgH2and Mg2FeH6, Mg2FeH6reduces the negative formation heat of the mixture compared with that of MgH2, which indicates that Mg2FeH6lowers the desorption temperature of MgH2through a catalytic effect and the milled powder containing duplex β-MgH2+Mg2FeH6exhibits the most rapid desorption rate among all the powders studied from TGA analysis.