Abstract's Details

The Effect of Cycling on Microstructure and Reaction Kinetics in Mg/MgH₂ Thin Films
Abstract ID	MAT-09
Presenter	Stephen Kelly
Presentation Type	Poster
Full Author List	S. T. Kelly (1), B. M. Clemens (1)
Affiliations	(1) Stanford University, MSE Department
Category	Materials Science
Abstract	Magnesium is an attractive material for hydrogen storage because it stores an appreciable amount of hydrogen (7.6 wt.%) as MgH₂, is abundant in the earth's crust and is relatively inexpensive. Understanding of the structural changes and associated kinetics for the magnesium/magnesium hydride phase transition is crucial to engineering practical metal hydride hydrogen storage materials involving magnesium. We have deposited epitaxial Mg films with Pd capping layers on (001) Al₂O₃ substrates using UHV sputter deposition. Using both in-situ and ex-situ XRD we examined the structural transformations, microstructural evolution and reaction kinetics of these thin films during repeated chargings and dischargings with gaseous hydrogen. As the films cycle between the hydride and metallic states, film texture degrades depending on the extent of charging and the reaction kinetics degrade with the texture. We also see evidence for multiple regrowth modes, including solid phase epitaxy, as the films discharge. The presence of the different modes depends on the film charging and discharging conditions.
Footnotes
Funding Acknowledgement	This work is supported by the DOE Metal Hydride Center of Excellence