Particle size distribution of Ni microprecipitates in LaNi5 used for hydrogen storage

Abstract
LaNi5 is an intermetallic compound which absorbs and desorbs hydrogen at convenient temperatures and pressures. It has been used for storing hydrogen fuel, and, using the heat of absorption, for various pump and heat engine applications. Recurrent absorption and desorption of hydrogen produces a phase separation into nickel metal and lanthanum hydride. We show from the magnetic behavior of degraded LaNi5 that a bimodal particle size distribution is present with all particles <(100 Å)3. The magnetic properties may be useful for determining the condition of LaNi5 in a reservoir.