Observation and Acoustic Emission Characteristics during Hydrogen Absorption Cracking in LaNi<SUB>4</SUB>Fe Alloy as Hydrogen Storage Material

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  • 水素貯蔵用合金LaNi<SUB>4</SUB>Feの水素吸収にともなう割れの直接観察とアコースティック・エミッション特性
  • 水素貯蔵用合金LaNi4Feの水素吸収にともなう割れの直接観察とアコースティック・エミッション特性
  • スイソ チョゾウヨウ ゴウキン LaNi4Fe ノ スイソ キュウシュウ ニ

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For a better understanding of the metal-hydride cracking process resulting in the active surface for hydriding, a study has been made on a bulk sample of LaNi4Fe which readily forms metal hydride under an atmospheric pressure of hydrogen at ambient temperature. The process of cracking and powdering of LaNi4Fe during hydriding under a flowing hydrogen of 0.1 MPa at room temperature was observed. Acoustic emission during hydriding was also measured in a wide frequency band (2 kHz–1 MHz) over a period of 4.02 ks.<BR>Various stages of the disintegration process in LaNi4Fe were photographed and AE signals were observed. The hydrogen absorption cracking fracture-surfaces of the metallic compound LaNi4Fe showed a brittle fracture surface with many microcracks. The screen classification of powdered sample indicated that an arc-melted bulk sample was partially disintegrated into a small powder below 37 μm in diameter during hydrogen absorption for 4.02 ks. AE events and energy-level histogram during hydriding were associated with the process of hydrogen absorption cracking and this process should be schematically divided into four stages on the basis of the acoustic emission characteristics. AE signals of higher energy-level corresponded to the appearence of macrocrack, and the emission source causing AE signals of lower energy-level was discussed.

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