Hydrogenation-induced microstructure changes of pseudo-binary (PrxMg1−x)Ni2 Laves compounds

• Published in: Journal of alloys and compounds Vol. 580; pp. S81 - S84
• Main Authors: Park, Ihho, Terashita, N., Abe, Eiji
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Kidlington Elsevier B.V 01.12.2013; Elsevier
• Subjects: Condensed matter: structure, mechanical and thermal properties; Convergent-beam electron diffraction, selected-area electron diffraction, nanodiffraction; Cross-disciplinary physics: materials science; rheology; Electron diffraction and scattering; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; Hydrogen-induced phenomena; Hydrogen-storage alloys; Laves compounds; Materials science; Nanocrystalline materials; Nanoscale materials and structures: fabrication and characterization; Physics; Solubility, segregation, and mixing; phase separation; Structure of solids and liquids; crystallography; Transmission electron microscopy; Hydrogen-storage alloys; Laves compounds; Transmission electron microscopy; Hydrogen-induced phenomena; Hydrogen storage; Electron diffraction; Amorphization; Solubility; Diffraction pattern; Hydrides; Hydrogenation; Phase separation; Hydrogen compounds; Laves phases; Microstructure; Nanocrystal
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2013.01.108

• We systematically investigate hydrogenation-induced microstructural changes of pseudo-binary (PrxMg1−x)Ni2 Laves compounds. • We use transmission electron microscopy (TEM), instead of X-ray diffraction techniques conventinally used so far. • We find a novel hydrogenation-induced phenomenon, which is hydrogenation-induced micro-phase separation (HIMPS). Using transmission electron microscopy (TEM), we systematically investigate hydrogenation-induced microstructural changes of pseudo-binary (PrxMg1−x)Ni2 Laves compounds varying x from 0.3 to 1.0, which lead to the averaged constituent atomic-size ratio RA/RB ranging 1.34–1.47 of the supposed AB2 compound. It is empirically known for the AB2 Laves compounds that hydrogen-induced-amorphization (HIA) takes place when the RA/RB exceeds 1.37. We find that, based on careful analyses of electron diffraction patterns and TEM images, the hydrogenation-processed microstructures of the (PrxMg1−x)Ni2 compounds exceeding the critical ratio are not pure amorphous but composed of Ni nano-crystals embedded in an amorphous matrix of hydride PrH2. This provides a direct evidence of hydrogenation-induced micro-phase separation (HIMPS), and accordingly it is suggested that HIA believed so far should be attributed to HIMPS phenomenon.