Effect of microstructure on hydrogen absorption in LaMg2Ni

Hydrogen absorption properties in LaMg2Ni compound are presented. Nanostructured phases have been obtained by crystallisation of an amorphous alloy, in order to study the influence of the microstructure on the absorption/desorption properties. In order to improve absorption kinetic, chemical etching has been also performed. The structural and hydriding properties were examined by X-ray diffraction, thermal analysis and hydrogen pressure-composition. An amorphous phase has been obtained from the LaMg2Ni phase by means of melt spinning technique. Crystallisation occurs in two stages at 500 K and 530 K. After crystallisation, a nanostructured phase has been obtained. Hydrogenation at 443 K leads to the formation of LaMg2NiH7, but at higher temperatures (523 K) LaHX is produced. Hydrogen pressure-composition isotherm of LaMg2Ni at 443 K is presented. The enthalpy of LaMg2Ni hydride formation was measured to be -47 kJ molH-1 by thermal analysis.