Mapping electrochemical activity in solid oxide fuel cells

The April 2017 issue's cover of Materials Today displays the Ni phase within a heterogeneous Ni-YSZ anode sample, using a distance-ordered homotopic thinning method in Avizo Fire software. X-ray tomography samples of ca. 50 mm in diameter were prepared from a bulk sample and an internal tomogram was collected from the Ni-YSZ sample: this was achieved using a lab-based X-ray nano-CT instrument with an isotropic voxel resolution of 32 nm. To obtain a tomogram many 2D radiograph projections are collected at discrete angular increments through rotation of the sample, these projections are then reconstructed using a filtered back-projection algorithm into a 3D volume of greyscale voxels. Once reconstructed the data was segmented according to greyscale into three phases, Ni, YSZ and pore. A centroid path was then mapped for the Ni phase using Avizo Fire software (FEI, France) by applying a medial axis-based method using distanceordered homotopic thinning (DOHT) where a skeletonisation is achieved through a combination of morphological thinning and distance mapping techniques. Inspecting the figure, the central node connecting many segments displays a large heterogeneous Ni particle while in contrast the empty region in the bottom left of the figure displays no paths as no Ni occupied this region.