Phase evolution,hydrogen storage thermodynamics and kinetics of ternary Mg90Ce5Sm5 alloy
来源期刊：JOURNAL OF RARE EARTHS2020年第6期
论文作者：Hui Yong Shihai Guo Zeming Yuan Wei Zhang Yan Qi Dongliang Zhao Yanghuan Zhang
文章页码：633 - 641
摘 要：Greatly stable thermodynamics and sluggish kinetics impede the practical application of Mg-based hydrogen storage alloys.The modifications of composition and structure are important strategies in turning these hydrogen storage properties.In this study,Mg-based Mg90Ce5 Sm5 ternary alloy fabricated by vacuum induction melting was investigated to explore the performance and the reaction mechanism as hydrogen storage material by X-ray diffraction（XRD）,scanning electron microscope（SEM）,transmission electron microscopy（TEM） and pressure-composition isotherms（PCI） measurements.The results indicate that the Mg-based Mg90Ce5 Sm5 ternary alloy consists of two solid solution phases,including the major phases（Ce,Sm）5 Mg41 and the minor phases（Ce,Sm）Mg12.After hydrogen absorption,these phases transform into the MgH2 and（Ce,Sm）H2.73 phase,while after hydrogen desorption,the MgH2 transforms into the Mg phase,but the（Ce,Sm）H2.73 phases are not changed.The alloy has a reversible hydrogen capacity of about 5.5 wt% H2 and exhibits well isothermal hydrogen absorption kinetics.Activation energy of 106 kJ/mol was obtained from the hydrogen desorption data between 573 and 633 K,which also exhibits the enhanced kinetics compared with the pure MgH2 sample,as a result of bimetallic synergy catalysis function of（Ce,Sm）H2.73 phases.The rate of hydrogen desorption is controlled by the release and recombination of H2 from the Mg surface.Furthermore,the changes of enthalpy and entropy of hydrogen absorption/desorption were calculated to be-80.0 kJ/mol H2,-137.5 J/K/mol H2 and 81.2 kJ/mol H2,139.2 J/K/mol H2,respectively.
Hui Yong1，Shihai Guo1，Zeming Yuan1,2，Wei Zhang1，Yan Qi1，Dongliang Zhao1，Yanghuan Zhang1,2
1. Department of Functional Material Research,Central Iron and Steel Research Institute2. Key Laboratory of Integrated Exploitation of Baiyun Obo Multi-Metal Resources,Inner Mongolia University of Science and Technology
摘 要：Greatly stable thermodynamics and sluggish kinetics impede the practical application of Mg-based hydrogen storage alloys.The modifications of composition and structure are important strategies in turning these hydrogen storage properties.In this study,Mg-based Mg90Ce5 Sm5 ternary alloy fabricated by vacuum induction melting was investigated to explore the performance and the reaction mechanism as hydrogen storage material by X-ray diffraction（XRD）,scanning electron microscope（SEM）,transmission electron microscopy（TEM） and pressure-composition isotherms（PCI） measurements.The results indicate that the Mg-based Mg90Ce5 Sm5 ternary alloy consists of two solid solution phases,including the major phases（Ce,Sm）5 Mg41 and the minor phases（Ce,Sm）Mg12.After hydrogen absorption,these phases transform into the MgH2 and（Ce,Sm）H2.73 phase,while after hydrogen desorption,the MgH2 transforms into the Mg phase,but the（Ce,Sm）H2.73 phases are not changed.The alloy has a reversible hydrogen capacity of about 5.5 wt% H2 and exhibits well isothermal hydrogen absorption kinetics.Activation energy of 106 kJ/mol was obtained from the hydrogen desorption data between 573 and 633 K,which also exhibits the enhanced kinetics compared with the pure MgH2 sample,as a result of bimetallic synergy catalysis function of（Ce,Sm）H2.73 phases.The rate of hydrogen desorption is controlled by the release and recombination of H2 from the Mg surface.Furthermore,the changes of enthalpy and entropy of hydrogen absorption/desorption were calculated to be-80.0 kJ/mol H2,-137.5 J/K/mol H2 and 81.2 kJ/mol H2,139.2 J/K/mol H2,respectively.
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