HYDRIDING OF MECHANICALLY ALLOYED MIXTURES OF MAGNESIUM WITH MNO2, FE2O3 AND NIO

The absorption-desorption characteristics towards hydrogen of mechanically alloyed mixtures containing 90 wt.% magnesium and 10 wt.% MnO2, Fe2O3 or NiO, respectively, have been investigated. Differences are established in the hydriding and dehydriding kinetics and the hydrogen capacity of the mixtures depending on the oxide component. It is shown that the highest absorption capacity corresponds to the MnO2-containing mixture. This sample also exhibits the highest hydriding and dehydriding rates. The mechanically alloyed NiO-containing sample has a lower hydrogen capacity, whereas the sample with Fe2O3 is characterized by the poorest desorption properties. The effects observed are explained on the basis of the difference in behaviour of the three oxides under the hydriding conditions.