Fig. 1 | Nature Communications

Fig. 1

From: Interface-mediated Kirkendall effect and nanoscale void migration in bimetallic nanoparticles during interdiffusion

Fig. 1

Heating-induced changes in the morphology of Au core–Pd shell (Au–Pd) nanoparticles (NPs). a In situ scanning transmission electron microscopy (STEM) images of the same NP after heating at 500 °C for 5 and 25 min, and their corresponding energy-dispersive X-ray (EDX) elemental maps. In the STEM images, voids show up as round areas of dark contrast. Dashed boxes highlight some of the voids that appeared in the NP during the heating. b (Left) Diffusion profiles extracted from the EDX measurements presented in the panel (a) and their respective error-function fits (black curves). (Right) Diffusion coefficients of Au diffusing in Pd obtained from extended studies (Supplementary Fig. 2), where we followed the diffusion of Au in these NPs as a function of temperature and time. The error bars indicate the standard deviation in the diffusion coefficients obtained at each temperature. An Arrhenius fit (black line) to the averaged diffusion coefficients gives the activation energy of Ea = 1.6 ± 0.2 eV. c In situ transmission electron microscopy (TEM) image sequence of a NP during heating to 500 and 600 °C. In the TEM images, the voids (highlighted with dashed boxes) show up as dark rings with a light core. d Images recorded after increasing the temperature to 650 °C (Supplementary Movie 1). The time-stamps are pegged to time in the movie. The position of the void denoted as 1 is tracked over 400 s in e. At t = 440 s, the void annihilated at the surface on the right of the NP

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