Experimental investigations of adsorption characteristics and porosity of activated metal hydride powders

In the present work non-uniformities of microstructure, porosity and adsorption characteristics of La_0.9Ce_0.1Ni₅ metal hydride by the height of the bed are investigated. A 500 g metal hydride bed was cycled inside a vertical metal hydride reactor and three samples was taken from top, middle and bottom of the bed. Non-uniform particle distributions and bed densification were observed, the bed porosity is around 0.58-0.67 at the top and middle parts of the bed and 0.46-0.54 at the bottom, where a dense and robust agglomerate was formed during the cycling. Specific surface area measured by nitrogen adsorption methods is 1.8-2.1 m²/g at the top of the bed, 4.2-5.4 m²/g in the middle and 1.1-1.5 m²/g at the bottom. The maximum is connected with higher degree of particle dispersion without effects from particle agglomeration. (paper)