Speaker
Description
Hydrogen as a fuel can be stored safely with high volumetric density in metals. It can, however, also cause embrittlement of metals. Understanding fundamental behavior of hydrogen at atomic scale is key to improve metal – metal hydride systems. However, currently, it is challenging to visualize hydrogen atoms. Here, we present our recent work in which we imaged for the first time hydrogen atoms at a metal – metal hydride interface and demonstrated a new techniques allowing robust imaging of hydrogen in metal hydrides [1]. The new technique is called integrated differential phase contrast, a recently developed technique for scanning transmission electron microscopy. To demonstrate the capabilities of the technique we studied titanium monohydride that forms thin and long plates inside titanium. The titanium – titanium monohydride interfaces are coherent, but large stresses are present perpendicular to the interfaces explaining the extreme aspect ratio of the plates and why they cause embrittlement of titanium. Images of the interface reveal remarkable stability of the hydride phase, originating from the interplay between interface coherence and stresses. We also uncovered, thirty years after three models were proposed, which one describes the position of the hydrogen atoms at the interface. Our work enables novel research on hydrides and is extendable to all materials containing combinations of light and heavy elements.
[1] Sytze de Graaf, Jamo Momand, Christoph Mitterbauer, Sorin Lazar, Bart J Kooi, Resolving hydrogen atoms at metal-metal hydride interfaces, Science Advances 6 (5), eaay4312, 2020, (DOI: 10.1126/sciadv.aay4312)
