Mechanical characterization of pristine and hydrogen-exposed palladium nanowires by in situ TEM.

Changes in the crystal lattice of palladium nanowires (Pd NWs) upon hydrogen exposure by absorption and interstitial introduction of hydrogen atoms within the matrix can induce swelling of the nanostructure and generate dislocations through the solid that may alter the overall mechanical performance of the material. Understanding the mechanical behavior of Pd NW-based hydrogen sensors may provide crucial information regarding material changes where the integrity of the sensing device can be compromised. The plastic behavior of hydrogen sensing Pd NWs was studied prior to-and subsequently to-hydrogen exposure via in situ transmission electron microscope-atomic force microscope (TEM-AFM) experiments to understand the role of hydrogenation in the NWs mechanical performance simultaneous to real-time observation. Quantitative and qualitative analysis was performed for deformed NWs upon compression and tension. Large plastic deformation was observed for pristine Pd NWs whereas little plastic deformation was observed for hydrogen-exposed Pd NWs. Tested pristine NWs behaved in a ductile manner, and necking events were observed for all tested specimens upon tension. Lowered ductility was observed for the hydrogen-exposed specimen, in accordance with hydrogen embrittlement observed in bulk palladium.