Self-ignition combustion synthesis of LaNi5 at different hydrogen pressures

In this paper, we describe the self-ignition combustion synthesis (SICS) of LaNi5 utilizing the hydrogenation heat of metallic calcium at different hydrogen pressures, and focus on the effect of hydrogen pressure on the ignition temperature and the initial activation of hydrogenation. In the experiments, La2O3, Ni, and Ca were dry-mixed, and then heated at 0.1, 0.5, and 1.0 MPa of hydrogen pressure until ignition due to the hydrogenation of calcium. The products were recovered after natural cooling for 2 h. The results showed that the ignition temperature lowered with hydrogen pressure. The products changed from bulk to powder with hydrogen pressure. This was probably caused by volume expansion due to hydrogenation at higher pressure. The product obtained at 1.0 MPa showed the highest hydrogen storage capacity under an initial hydrogen pressure of 0.95 MPa. The results of this research can be applied as an innovative production route for LaNi5 without the conventional melting of La and Ni.

► Combustion synthesis of LaNi5 at different hydrogen pressures.
► Ignition temperature lowered with hydrogen pressure.
►  Products changed from bulk to powder with hydrogen pressure.
► Initial activity depended on the hydrogen pressure charged in the production.