Microstructure reconstruction and homogenization of porous Ni-YSZ composites for temperature dependent properties

Abstract

In this work, a 3D microstructure of a porous Ni–YSZ composite is reconstructed using a recently developed Monte Carlo methodology. The 3D reconstruction starts by analyzing 2D SEM micrographs of real composite materials, which yield initial nucleation sites for different phases. The so-called cellular automaton algorithm, which is observed in insect colonies and bacteria growth in nature, controls growth kinetics of the initial nuclei. After successful growth and completion of the reconstruction process, FEM simulations are applied to characterize elastic and thermal properties of the reconstructed material. A porous Ni–YSZ composite reconstructed by this method shows mechanical behavior in between full isotropic and full orthotropic with an average Young's moduli of 17 GPa at room temperature and 10.2 GPa at 1000 °C, which are consistent with experimentally reported values. The variation in effective shear and Poisson's moduli as a function of temperature is also studied. Thermal conductivity and thermal expansion coefficient of the digital material are derived as functions of temperature; revealing a relatively isotropic property in thermal conductivity and an increase in anisotropy in thermal expansion coefficient by increasing temperature.