Figure 2: In situ observation of structural and compositional changes during Ni2Co oxidation.
From: Interrogation of bimetallic particle oxidation in three dimensions at the nanoscale
(a) In situ ADF-STEM images of one particle in the first oxidation stage show the elemental migration from the inside of the particle to the surface, resulting in the formation of a core-shell structure. The in situ EELS mapping of O, Co and Ni elements shows that the shell consists of a Ni and Co binary oxide with a few Co oxide nanodomains on the outside. (b) In situ ADF-STEM images of the particle during further oxidation show the oxidation of the inside core. The O, Co and Ni elemental distribution in the fully oxidized sample shows that the particle is encased by Co-rich oxides. (a) and (b) are from different particles. (c) A series of cross-sections and isosurfaces created by the electron tomography technique allow visualization of the internal structure of partially oxidized particle. Scale bar, 50 nm.
