Stability of the Hydrogen Absorption and Desoption Plateaux in LaNis-H Part 3: Experimental Observations of Compositional Inhomogeneities Due to Temperature Gradients
Abstract
It has been predicted by Pons and Dantzer that temperature gradients due to the released enthalpy of H absorption-desorption will generate macroscopic inhomogeneities of the αβ phase proportions in metal hydrides. We used in situ X-ray diffraction and in situ neutron diffraction respectively to study the growth of β-LaNi5H at the free surface, and β-LaNi5-D in the bulk of powdered samples. It was found that a macroscopic compositional inhomogeneity does occur, and can be so severe that the free surface of the sample remains pure α phase while the bulk of the sample is rich in β phase.It has been predicted by Pons and Dantzer that temperature gradients due to the released enthalpy of H absorption-desorption will generate macroscopic inhomogeneities of the αβ phase proportions in metal hydrides. We used in situ X-ray diffraction and in situ neutron diffraction respectively to study the growth of β-LaNi5H at the free surface, and β-LaNi5-D in the bulk of powdered samples. It was found that a macroscopic compositional inhomogeneity does occur, and can be so severe that the free surface of the sample remains pure α phase while the bulk of the sample is rich in β phase.
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Journal Title
Journal of Alloys and Compounds
Volume
217
Issue
1
Subject
Physical sciences
Condensed matter physics
Materials engineering
Resources engineering and extractive metallurgy