Hydriding behavior of F-treated Mg2Ni at moderate conditions

The F-treatment effects on the initial activation characteristics and on the cyclic hydriding-dehydriding behavior of the Mg2Ni alloy as a function of temperature, pressure and particle size have been investigated. Metallographic studies have also been performed. It was found that with the formation of magnesium fluoride on the particle surface, some microchannels were generated along the interfaces of the Mg-rich Mg + Mg2Ni eutectic structure. These are believed to contribute to the rapid initial activation at low temperatures, such as 30 degrees C, and to the only partial hydriding ability, which increases slightly with increasing temperature, pressure and number of cycles. Small-size powders are effective in improving the initial activation performance, but not the hydriding cyclic behavior. A growth process of the hydride phase from the surface to the bulk associated to cycling and resulting from the cracking growth of the bulk was suggested.