THE CHANGES OF HYDROGENATION PROPERTIES INDUCED BY THERMAL CYCLINGS IN MMNI4.5AL0.5 AND MMNI4.15FE0.85

The changes in hydrogenation properties of MmNi//4//. //5Al//0//. //5 and MmNi//4//. //1//5Fe//0//. //8//5 induced by thermal cycling were investigated through P-C-T curve measurements. Hydrogen storage capacity was decreased by 7. 6% for MmNi//4//. //5Al//0//. //5 and 6% for MmNi//4//1//. //5Fe//0//. //8//5 after 3000 cycles from 303 to 423 K and from 198 to 333 K respectively. Plateau slope and hysteresis were slightly increased, while the plateau region was still retained. The degradation rate due to thermal cycling was not affected after recovery treatment but the capacity after recovery was decreased gradually as the number of recovery treatments were increased.