Hydrogen Storage Characteristics of FeTi Containing Zirconium

The effect of Zr addition to FeTi on the initial hydriding process, the pressure-composition isotherms and the microstructure was investigated. The partial substitution of Zr (1∼15 at%) for Fe, Ti or both enhanced the activation of FeTi and it hydrided at 303 K after a short incubation time without any heat treatment. All the alloys were composed of FeTi and other two phases. The FeTi phase contained almost no Zr and the changes in the plateau pressure caused by the addition of Zr were not pronounced. The other two phases contained rather large amounts of Zr and the compositions of these phases can be approximately represented by (Ti1−yZry)2Fe and (Fe1−wZrw)2Ti, respectively. The former phase readily reacted with hydrogen and the latter phase did not react with hydrogen. The results obtained in this study show that the presence of the (Ti1−yZry)2Fe phase in the alloy plays a crucial role in shortening the incubation time, but decreases the hydrogen storage capacity of the alloy because the hydride of (Ti1−yZry)2Fe phase is too stable to decompose at the temperature and pressure used in this study.An FeTi alloy with good performance was obtained by the dispersion of small amounts of the (Ti1−yZry)2Fe phase as fine particles in the alloy. That is, the rapidly cooled Fe0.98TiZr0.02 alloy, which is estimated to contain about 5 mol% (Ti1−yZry)2Fe phase in the alloy, was activated after a short incubation time at room temperature with its hydrogen storage capacity as large as the un doped FeTi alloy.