Molecular scale insight of pore morphology relation with mechanical properties of amorphous silica using ReaxFF
T Vo and B He and M Blum and A Damone and P Newell, COMPUTATIONAL MATERIALS SCIENCE, 183, 109881 (2020).
Porous materials are typically heterogeneous and they contain large variations of micro-/nano-pore structures, causing complicated behaviors. In continuum models, most mechanical properties of porous materials are estimated based on porosity, while the variations of micro/nano structures are ignored. That could be problematic as the microscopic heterogeneity may affect the mechanical response of porous materials. Thus, understanding micro/nano heterogeneity impact has been the focus in many scientific and engineering subjects. In the present study, we investigated the effect of nanopore structure (including pore shape and orientation) as well as porosity on mechanical properties of amorphous silica (a-SiO2). The pore sizes in our simulations are comparable to the corresponding ones observed in a-SiO2 based materials. We found that the existing of nanopores strongly influences Young's modulus (E) and critical energy release rate (G(IC)). These properties decrease with increasing porosity. Importantly, the impact of nanopores was characterized by structural parameters of porous materials. In addition to dependency on porosity, Young's modulus also was found to vary as a function of potential energy per atom, which highly depends on nanopore shape. Furthermore, critical energy release rate was found to increase with increasing ligament length (also known as pore wall thickness). The results highlighted the importance of nanopore structures, which must be taken into account when studying fracture mechanisms in porous materials. Based on our findings, it was proposed that mechanical properties of porous materials can be controlled by nano-engineering pore structures.
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