Investigations on the nitrogen storage property of LaNi5 powder

The nitrogen absorption and desorption property of LaNi5 was investigated using NH3 and N2 as nitrogen sources. It was found that both as purchased and milling processed LaNi5 powder can absorb and desorb nitrogen using NH3 as the nitrogen source, while milled LaNi5 powder can absorb and desorb more. XRD, cross sectional SEM and EPMA were performed to elucidate the nitrogen stored phases. When N2 gas was used as the nitrogen source, it was found that the amount of absorbed nitrogen significantly decreased. By using high pressure for the absorption treatment or performing an activation treatment using hydrogen absorption/desorption before the nitrogen absorption treatment, milled LaNi5 was found to absorb nitrogen of 0.1 mol/mol Finally, the mechanism of the nitrogen absorption was discussed from the EPMA and kinetic data of the nitrogen absorption, and it was suggested that the mechanism of the nitrogen absorption might be explained by a combined model of a diffusion controlled process and an interface controlled process.