Kinetic properties in hydrogenation of FeTi intermetallic compound before and after complete activation were studied by using volumetric method.
As the results of observation the first hydrogen absorption curves of compacted FeTi sample only and compacted FeTi sample with Al powder or Mn powder, it was recognized that activation was enhenced by compacting FeTi powder with Al or Mn powder. This results could be interpreted as that Al or Mn powder contacted with FeTi surface contributed to breaking the surface oxygen (or oxide) film by surface oxidation reaction during the activation heat treatment.
The hydrogen storage capacity, while, was not affected by compacting FeTi powder with Al or Mn powder. The hydrogen absorption curves during hydrogen absorption desorption cycle were dependent strongly on surface oxygen content and hydrogen amount absorbed at previous cycle.
From above results the activation mechanism was suggested.
The investigations of hydriding kinetic properties of FeTi were carried out after complete activation, and the experimental results were analyzed by comparing with theoretical results established. Hydrogen absorption rate was affected significantly by vacuum time for desorption or hydrogen amount existing in the FeTi sample. The absorption rate increased as vacuum time was shorter, as hydrogen amount existing in the FeTi sample was more and as the reacted fraction increased at initial stage of reaction. These results could be interpreted by time dependent nucleation.
The dependence of hydrogen absorption rate on hydrogen pressure and temperature showed that time dependent chemisorption of hydrogen molecules on sample surface is rate controlling, and the apparent activation energy of the chemisorption was about 1.5 Kcal/mole $H_2$. While, at later stage of reaction rate controlling changed from chemisorption to hydrogen diffusion through hydride phase.
