Phase structure and hydrogen storage properties of LaMg3.93Ni0.21 alloy
The phase structure and hydrogen storage property of LaMg3.93Ni0.21 alloy were studied. XRD and SEM results exhibited that LaMg3.93Ni0.21 alloy consisted mainly of LaMg3, La2Mg17 and LaMg2Ni phases; after hydriding/dehydriding process, all the three phases transformed, La3H7 phase existed and the ac...
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Published in | Journal of rare earths Vol. 30; no. 6; pp. 534 - 539 |
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Main Author | |
Format | Journal Article |
Language | English |
Published |
Elsevier B.V
01.06.2012
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Subjects | |
Online Access | Get full text |
ISSN | 1002-0721 2509-4963 |
DOI | 10.1016/S1002-0721(12)60086-6 |
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Summary: | The phase structure and hydrogen storage property of LaMg3.93Ni0.21 alloy were studied. XRD and SEM results exhibited that LaMg3.93Ni0.21 alloy consisted mainly of LaMg3, La2Mg17 and LaMg2Ni phases; after hydriding/dehydriding process, all the three phases transformed, La3H7 phase existed and the actual hydrogen absorption phases were Mg and Mg2Ni phases. Pressure-composition-temperature (P-C-T) measurement showed that the reversible hydrogen storage capacity of LaMg3.93Ni0.21 alloy was 2.63 wt.%, and the absorption time for reaching 90% of the storage capacity was 124 s at 523 K, and it was 1850 s for deabsorbing 90% of the maximum dehydrogen capacity. The hydriding process of LaMg3.93Ni0.21 alloy followed the nucleation and growth mechanisms. The enthalpy and entropy for hydriding and dehydriding reactions of the Mg phase in LaMg3.93Ni0.21 alloy were calculated to be 456.38±1.10 kJ/mol H2, -100.96±1.96 J/(K·mol) H2 and 68.50-x3.87 kJ/mol H2, 98.28 ±5.48 J/(K-mol) H2, respectively. A comparison of these data with those of MgHz (-74.50 kJ/mol H2, -132.30 J/K.mol H2) suggested that the hydride of LaMg3.93Nio.21 alloy was less stable than MgH2. The existence of La hydride and synergetic effect of multiphase led to higher reversible hydrogen storage capacity and better kinetic property at lower temperature for LaMg3mNi0.21 alloy. |
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Bibliography: | 11-2788/TF The phase structure and hydrogen storage property of LaMg3.93Ni0.21 alloy were studied. XRD and SEM results exhibited that LaMg3.93Ni0.21 alloy consisted mainly of LaMg3, La2Mg17 and LaMg2Ni phases; after hydriding/dehydriding process, all the three phases transformed, La3H7 phase existed and the actual hydrogen absorption phases were Mg and Mg2Ni phases. Pressure-composition-temperature (P-C-T) measurement showed that the reversible hydrogen storage capacity of LaMg3.93Ni0.21 alloy was 2.63 wt.%, and the absorption time for reaching 90% of the storage capacity was 124 s at 523 K, and it was 1850 s for deabsorbing 90% of the maximum dehydrogen capacity. The hydriding process of LaMg3.93Ni0.21 alloy followed the nucleation and growth mechanisms. The enthalpy and entropy for hydriding and dehydriding reactions of the Mg phase in LaMg3.93Ni0.21 alloy were calculated to be 456.38±1.10 kJ/mol H2, -100.96±1.96 J/(K·mol) H2 and 68.50-x3.87 kJ/mol H2, 98.28 ±5.48 J/(K-mol) H2, respectively. A comparison of these data with those of MgHz (-74.50 kJ/mol H2, -132.30 J/K.mol H2) suggested that the hydride of LaMg3.93Nio.21 alloy was less stable than MgH2. The existence of La hydride and synergetic effect of multiphase led to higher reversible hydrogen storage capacity and better kinetic property at lower temperature for LaMg3mNi0.21 alloy. hydrogen storage alloy; phase transition; hydriding kinetic; thermodynamic property; microstructure; rare earths |
ISSN: | 1002-0721 2509-4963 |
DOI: | 10.1016/S1002-0721(12)60086-6 |