Mechanical alloying and electronic simulations of 2Mg-Fe mizture powders for hydrogen storage
2Mg-Fe powder mixture was milled in hydrogen atmosphere to prepare materials for hydrogen storage. The microstructure and dehydrogenating properly of the milled sysiem 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)H2 solid solutions and Mg2FeH6 compound, the forming process of Mg2FcH6 was assumed as that magnesium was first dissolved in some H atoms to form MgH2, second, iron atom progressively dissolved into MgH2 lattice to form (MgFe)H2 solid solutions, finally the (MgFc)H2 solid solution can be changed into Mg2FeH6 phase. 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 MgH2 phase is still the major phase in the coexistence mixtures of two types of hydrides β-MgH2 and Mg2FeH6, Mg2FeH6, reduces the negative formation heat of the mixture compared with that of MgH2, which indicates that Mg2FeHe lowers the desorption temperature of MgH2 through a catalytic effect and the milled powder containing duplex β-MgHi+Mg2FeH6 exhibits the most rapid desorption rate among all the powders studied from TGA analysis.
Hydrogen storage materials Mechanical alloying Heat of formation Electronic structure First-principles calculation
D.W.Zhou S.L.Li R.A.Varin P.Peng J.S.Liu F.Yang
School of Materials Science and Engineering, Hunan University, Changsha 410082, P.R.China State Key Laboratory for Powder Metallurgy.Cent rul South University, Changsha 410083, P.R.China Department of Mechanical Engineering, University of Waterloo, Waterloo, Ont., Canada N2L 3G1
国际会议
广州
英文
1131-1140
2008-11-01（万方平台首次上网日期，不代表论文的发表时间）