Hydriding behavior of gas-atomized AB(5) alloys

The hydriding characteristics of some AB(5) alloys produced by high pressure gas atomization (HPGA) have been examined during reactions with hydrogen gas, and in electrochemical cells. The hydrogen storage capacities and the equilibrium pressures for HPGA processed LaNi5, LaNi4.75Sn0.25, and MmNi(3.5)Co(0.8)Al(0.4)Mn(0.3) alloys (where Mm denotes Mischmetal) are found to be nearly identical to annealed alloys produced as ingots. The large discontinuous volume change across the alpha-beta plateau region for gas-atomized LaNi5Hx was seen to produce extensive fracturing in all but the smallest alloy spheres. However, only the largest spheres of the gas-atomized MmNi(3.5)Co(0.8)Al(0.4)Mn(0.3) and LaNi4.75Sn0.25Hx alloys exhibited any discernible fracturing. The maximum electrochemical storage capacities of the gas-atomized LaNi4.75Sn0.25 and MmNi(3.5)Co(0.8)Al(0.4)Mn(0.3) alloys were found to be smaller than the capacities of annealed alloys prepared from ingots.