Bulk alloys, pulverization

LaNij was cycled 1,000 times, the plateau pressures at 90, 110, and 130°C were only slightly changed, while a significant degradation of absorption kinetics was observed. The pulverization of the bulk alloys occurred, and the volume mean particle diameter was reduced from -35 pm before to -11 pm after 1,000 cycles. The changes in properties were explained by disproportionation and pulverization phenomena and the effect of impurities in the hydrogen used for charging. 

The processing of most ores involves a series of standardized steps. After mining, the bulk ore is processed to remove any gangue (excess waste rock and minerals). This processing typically consists of pulverizing the ore to a relatively fine state, followed by some form of gravity separation of the metals from the gangue [ 134-140]. The refined ore is processed thermally to separate the metal and non-metal constituents, and then further reduced to the free metal Since most of these metals are unsuitable for use in a pure state, they are subsequently combined with other elements and compounds to form alloys with the desired properties. 

Essentially all metals and alloys which form metallic hydrides require an activation process before the metal wiU readily cycle between the hydride and metal phase. All the ABs and AB2 alloys are quite brittle and during the activation procedure are pulverized to fine particles. This greatly enhances subsequent reaction rates. The activation process is considered to take place in two stages the formation of a reactive surface and pulverization of the bulk solid to form fine particles. The surface composition of LaNis after activation has been defined by X-ray photoemission spectroscopy. Auger electron spectroscopy, and magnetic susceptibility studies [19]. There is a surface enrichment of La to give a ratio of La/Ni 1 the La is associated... 

---