Katsuhisa Matsuzaki

Three-Dimensional Numerical Simulation of Ni-YSZ Anode Polarization Using Reconstructed Microstructure from FIB-SEM Images

The overpotential in a three-dimensional Ni-YSZ anode model structure obtained by a dual-beam focused ion beam-scanning electron microscope is predicted by lattice Boltzmann method. Gaseous, ionic and electronic transport equations with electrochemical reaction at the three-phase boundary are solved with an assumption of local equilibrium in the solid oxide. The gas transport is modeled by a so-called dusty gas model. The numerical simulation is performed under the current density conditions of 0.01, 0.1, 0.3 and 0.7 A/cm. Three-dimensional electrochemical potential distributions inside a test anode microstructure are presented. The proposed method can be used for predicting SOFC electrode polarization.

Quantification of Ni-YSZ Anode Microstructure Based on Dual Beam FIB-SEM Technique

The three-dimensional microstructure of an SOFC anode is quantified using a dual beam focused ion beam scanning electron microscopy (FIB-SEM) system equipped with an energy dispersive X-ray spectroscopy (EDX) unit. The microstructure of the Ni–YSZ anode is virtually reconstructed in a computational field using a series of acquired two-dimensional SEM images. The three-phase boundary (TPB) density and tortuosity factors are carefully evaluated by applying two different evaluation methods to each parameter. The TPB density is estimated by a volume expansion method and a centroid method, while the tortuosity factors are evaluated by a random walk calculation and a lattice Boltzmann method (LBM). Estimates of each parameter obtained by the two methods are in good agreement with each other, thereby validating the reliability of the analysis methods proposed in this study.