EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

In porous anodes of solid oxide fuel cells (SOFCs), correlation between heterogeneous pore structure and its permeability is investigated. Pore former was added during the fabrication of the anodes to form heterogeneous pore structure with bimodality in their pore-size distributions. The degree of Knudsen effect varies depending on the local pore size in the heterogeneous pore structure. The pore structures of the anodes were analyzed in 3D using the focused ion beam and scanning electron microscopy (FIB-SEM) and their microstructure was quantitatively analyzed. The quantified microstructural parameters indicate that increasing the amount and size of the pore former increases the porosity and mean pore size, reducing the complexity of the pore structure. From the analysis of the pore-size distribution, the pore structure in the porous anodes fabricated with pore former consists of two types of structures; one is formed at sintering and reduction of the particles and has fine pores around 1 µm (Pore_REF), and the other is formed by pore former and has relatively large pores around 2-5 µm (Pore_PF). However, because the volume ratio of Pore_PF to the whole pores is close to unity, the main flow path in the porous anodes is mainly formed by Pore_PF. Permeability of the porous anode is evaluated in experiment on the basis of the Darcy’s law by applying a pressure difference across the anodes pellets and measuring the permeation flow rate. The results indicate that decreasing the complexity of the pore structure increases the permeability. From the correlation between the pore-size distribution and the permeability, it is found that the permeation flow rate is limited by the structure with Pore_REF when the main flow paths formed by Pore_PF are connected only by Pore_REF.