Solid oxide fuel cell (SOFC) is expected as a promising energy conversion device because of its high efficiency and fuel flexibility.  It is widely known that electrode microstructures are of great importance for attaining high performance as well as high reliability of SOFCs.  In the SOFC fabrication processes, sintering of sub-micron scale ceramic and metallic powders is one of the most important step to achieve efficient and reliable electrodes. In addition, microstructural changes in SOFC anodes associated with particle sintering during high temperature operation may lead to severe performance degradation. Thus, in order to develop more reliable electrodes of SOFC, a method that can offer quantitative information of sintering behavior at the sub-micron scale is highly demanded.

Accurate prediction of microstructure evolution during sintering, even in single-phase systems, is still very challenging. This is because sintering behavior is deeply affected by the three-dimensional (3D) complex geometries of the powder compacts, such as grain and pore size distributions, their shapes, relative density and coordination number, etc. Among many types of numerical approaches, a mesoscale kinetic Potts Monte Carlo (KMC) method has the potential to overcome this difficulty [1]. This method is capable of capturing three dimensional microstructural evolution from the initial to the final stages of solid-state sintering.  However, the underlying kinetics at the sub-micron scale are not yet completely understood. Validation of the results using quantitative 3D microstructure data is indispensable to develop a numerical simulation tool which can reproduce proper sintering trajectory of real powder sintering.

In the present study, KMC simulations of nickel (Ni) and nickel oxide - yttria stabilized zirconia (NiO-YSZ) composite are carried out starting from the green powder microstructure obtained using focused ion beam - scanning electron microscopy (FIB–SEM). Quantitative topological changes during sintering of real powder compacts are obtained by FIB–SEM. This technique offers a great advantage because of its high resolution, which is sufficient to capture the 3D geometric nature of sub-micron-sized powder compacts (typically < 1/10 of the powder size). The simulated temporal trajectories of microstructural parameters are compared with the experimental data from FIB-SEM to verify the numerical modeling results.

[1] Hara, S., Ohi, A. and Shikazono, N., Sintering Analysis of Sub-Micron-Sized Nickel Powders: Kinetic Monte Carlo Simulation Verified by FIB-SEM Reconstruction, J. Power Sources, 276, pp. 105-112 (2015).