LI Wuhui1), TIAN Baohong2), MA Ping1), WU Erdong1)
1) Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016
2) School of Materials Science and Engineering, Henan University of Science and Technology, Luoyang 471003
Cite this article:
LI Wuhui TIAN Baohong MA Ping WU Erdong. HYDROGEN STORAGE PROPERTIES OF ScMn2 ALLOY. Acta Metall Sin, 2012, 48(7): 822-829.
Abstract As an important rare--earth type Laves phase compound, ScMn2 alloy is endowed certain significance in the viewpoint of either theoretical or applicable investigation. In this study, the structures of ScMn2 alloy and its hydride (deuteride) are characterized by XRD. The hydrogen activation properties, pressure-concentration-temperature (P-C-T) curves and absorption kinetic curves of ScMn2 alloy are measured using Sieverts-type hydrogenator. The desorption kinetics of the passivated hydride are determined by TG-DSC. The results show that the hydride and deuteride of the alloy retain the C14 type Laves phase structure of the parent alloy, with the volume expansions of about 25%. ScMn2 possesses outstanding activation properties and can react quickly with hydrogen (deuterium) at room temperature and atmospheric pressure. The hydrogen and deuterium storage capacities of 1 mol ScMn2 are about 3.7 mol H and 3.6 mol D at 100 kPa and 298 K. ScMn2 has low hysteresis critical temperature for absorption and desorption, good plateau characteristics and relatively low plateau pressure, hence it is suitable for the storage of hydrogen isotopes. The enthalpy and entropy for formation of ScMn2 hydride at concentration corresponding to room temperature plateau pressure are -45 kJ/mol and -80 J/(K?mol), respectively. The hydriding kinetics of the alloy can be interpreted by Johnson-Mehl-Avrami (JMA) model, with the estimated reaction order of 0.4. The apparent activation energies for hydriding and deteuriding process are estimated to be (16±0.3) and (19±1.7) kJ/mol, respectively, the observed isotope effect on kinetics can possibly be applied to separation of hydrogen isotope. The passivated hydride can release completely at 639 K and the corresponding apparent activation energy is (144±14) kJ/mol.
