Multi-scale pore network modelling to evaluate connectivity in ceramic composites

Complex morphologies, such as open or connected feature networks, are present in a wide variety of materials. Characteristics of these networks can impact key performance attributes of the materials themselves, affecting transport properties such as thermal conductivity. Therefore, it is critical to analyze the microstructure of these materials to gain a better understanding of the fundamental characteristics of the morphology. This study utilized pore network modeling as a method to extract morphological information on the solid network formed by boron nitride ceramic flakes in a polymeric resin matrix and uses the characteristics of the model to analyze the connectivity of the flakes. In this work, Micro-CT and FIB/SEM tomography were used in tandem to provide complimentary analyses of the microstructure and nanostructure, respectively, of the flake network to understand how this may contribute to transport properties of the material. Rather than a pore network model (PNM), the flake network model (FNM) was extracted from the tomographic datasets and the coordination number distribution was determined for the flakes detected in each. Micro-CT analysis showed that the flakes had formed a cage-like network around the exterior of the sample with limited connectivity in the interior, likely due to flake agglomeration at the outer surface of the material. A comparison of the full and interior-only Micro-CT FNMs indicated lower connectivity in the interior. This was confirmed by flow rate models generated from the network analysis for the flake contact points. The FNM extracted from the FIB/SEM tomography dataset exhibited similar connectivity compared to the interior-only FNM, indicating that the connectivity of the material was consistent when measured at the micron scale and at the nanometer scale.