Microstructures and hydrogen absorption–desorption behavior of an A2B7-based La-Mg-Ni alloy. (24th August 2017)

• Record Type: Journal Article
• Authors: Wu, Z.; Kishida, K.; Inui, H.; Ishida, J.; Yasuoka, S.; Zhang, Z.
• Is Part Of: International journal of hydrogen energy. Volume 42:Number 34(2017)
• Page Start: 22159
• Page End: 22166
• Publication Date: 2017-08-24
• Subjects: A2B7-type structure -- Microstructure -- Hydrogen storage -- Irreversible capacity; Hydrogen as fuel -- Periodicals; Hydrogène (Combustible) -- Périodiques; Hydrogen as fuel; Periodicals; 665.81
• DOI: 10.1016/j.ijhydene.2017.04.023
• Languages: English
• ISSNs: 0360-3199

Abstract

Abstract: The microstructural changes during hydrogen absorption–desorption cycles of an A2 B7 -based La-Mg-Ni alloy with a nominal composition of La1.5 Mg0.5 Ni7.0 were systematically investigated by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM). The ternary La-Mg-Ni alloy was mostly composed of 2 H -A2 B7 phase with minor inclusions of 3 R -A5 B19, 2 H -A5 B19 and 3 R -AB3 phases existing as parts of intergrowth structures with the major A2 B7 phase. Most parts of the major 2 H -A2 B7 phase containing Mg exhibited an excellent crystal structure retention after the hydrogen absorption–desorption cycles at 80 °C. Two types of defected bands were found to develop after the first hydrogen absorption–desorption cycle. The first ones are amorphous bands developed inside the minor 3 R -AB3 phase, while the second ones develop as heterogeneously strained regions inside the major 2 H -A2 B7 phase. Both the defected bands are considered to be responsible for the irreversible hydrogen capacity of the A2 B7 -based La1.5 Mg0.5 Ni7.0 alloy during the hydrogen absorption–desorption cycles at 80 °C. Highlights: A La-Mg-Ni ternary alloy with the major 2 H -A2 B7 phase was prepared. The role of Mg is to retain structure for excellent cycle stability during the cycles. The reason for irreversible capacity of A2 B7 -based alloy was discussed from defects.