Abstract
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.
Highlights
Solid state hydrogen storage in metal hydrides is a promising form of energy storage for stationary machines, backup power, and for heavy duty vehicles
The effect of the zirconium on TiFe alloy was investigated from the perspective of improving the activation of this system
The addition of 4 wt.% zirconium is the minimum threshold in order to activate the compound without any pre-treatment
Summary
Solid state hydrogen storage in metal hydrides is a promising form of energy storage for stationary machines, backup power, and for heavy duty vehicles. In these applications, the system safety, low maintenance, compactness, and operating costs far exceed the criteria of high gravimetric hydrogen capacity. TiFe alloy has poor activation characteristics, needing time, high pressure, and high temperature to achieve full hydrogenation [3]. This is a major concern for commercial and industrial applications. In order to overcome this problem, different approaches have been investigated. They include pulse current-assisted reaction [4], ball milling [3,5], plastic deformations [6], and utilizing clusters [7]
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