세미나

In-situ transmission electron microscopy (TEM) technique allows us to direct visualize dynamic process of materials under the working conditions with atomic resolution. In this talk, I will introduce in-situ TEM systems and on-going research regarding the discovery and observation of metal-hydrides using it.

I discovered new metastable hexagonal close-packed (HCP) palladium-hydride (PdH_x) phase in liquid cell TEM [1]. I verify the metastable HCP structure is stabilized under the higher hydrogen concentration supplied by radiolysis effect coming from the interaction between high energy electron beam and liquid. Also, I confirm the different characteristics of HCP PdH compared to its thermodynamically stable FCC counterpart.

In addition, I will show the dynamic process of Mg-hydrides which is promising candidates for solid-state hydrogen storage system due to its good reversibility, relatively low working pressure and gravimetric density. I directly observed the dehydrogenation of MgH₂/Mg₂FeH₆ composite by in-situ TEM [2]. I confirm the dehydrogenation kinetics of both phases with in-situ TME that has a higher spatial and temporal resolution which shows catalytic effect of Fe on MgH₂.

Understanding the hydrogen dynamics in metal together with the relationship between crystal structure and material properties will open up new avenues in metal-hydrides and allow the rational design rule of novel materials.