Hydrogenation Properties of TiFe Doped with Zirconium
The goal of this study was to optimize the activation behaviour of hydrogen storage alloy TiFe. We found that the addition of a small amount of Zr in TiFe alloy greatly reduces the hydrogenation activation time. Two different procedural synthesis methods were applied: co-melt, where the TiFe was melted and afterward re-melted with the addition of Zr, and single-melt, where Ti, Fe and Zr were melted together in one single operation. The co-melted sample absorbed hydrogen at its maximum capacity in less than three hours without any pre-treatment. The single-melted alloy absorbed its maximum capacity in less than seven hours, also without pre-treatment. The reason for discrepancies between co-melt and single-melt alloys was found to be the different microstructure. The effect of air exposure was also investigated. We found that the air-exposed samples had the same maximum capacity as the argon protected samples but with a slightly longer incubation time, which is probably due to the presence of a dense surface oxide layer. Scanning electron microscopy revealed the presence of a rich Zr intergranular phase in the TiFe matrix, which is responsible for the enhanced hydrogenation properties of these Zr-doped TiFe alloys.
Hydrogenation improvement of TiFe by adding ZrMn2
Abstract In this paper, we report the microstructure and hydrogen storage properties of TiFe + x wt.%ZrMn 2 (x = 2, 4, 8, 12) alloys prepared by arc melting. Each alloy was made of two phases: a TiFe phase with very small amount of zirconium and manganese, and a second phase which has a higher proportion of zirconium and manganese. We found that the first hydrogenation kinetics increase with x. This is most likely due to the presence of zirconium-rich secondary phase that acts as a gateway for hydrogen to enter the main TiFe phase. Pressure-composition isotherms also show that increasing x decreases the absorption plateau pressure. Moreover, for x = 12, air exposure had a minimal impact on hydrogen absorption behaviour. Finally, we found that cold rolling has minimal effect on the activation kinetics of TiFe + x wt.%ZrMn 2 (x = 4) alloy.
Mechanical activation of hydrogen sorption with intermetallic compounds LaNi5 and TiFe in powder systems
Abstract Results of the experimental investigation of the influence of mechanical activation and catalytic factor on the hydrogen sorption process of intermetallic compounds LaNi5, TiFe and compositions on their base are presented. The intensification of hydrogen sorption is shown to proceed in compacts of the LaNi5 powder and mixtures of LaNi5 with a metal catalyst. Pressing of coarse TiFe powders allows one to activate them at room temperature. This is caused by the formation of a fresh intermetallic surface during the pressing.