Scaling the Elastic Properties of Silica Aerogels: A Modelling Insight

Abstract

The computational modelling of silica aerogels has the potential to investigate mesoporous phenomena that are difficult to accurately probe from experimental investigations. One such phenomena, the scaling behavior of the elastic modulus to density (E∝ ρ^α) in silica aerogels has been a keen research topic. Conventional open-porous materials like foams typically exhibit exponent α=2, however, for silica aerogels the value of the exponent α is typically observed to be between 3-4 [1]. While there have been several insights and discussions into the possible explanation behind this observed extraordinarily large exponent; the effect of spatial arrangement of the particles and the pearl-like necklace morphology of the pore wall remain unexplored. This influence can be effectively modelled with computational modelling of the silica aerogel microstructure and then performing finite element calculation for their mechanical properties. As such, while some research has focused on application of Brownian motion-based diffusion limited cluster-cluster aggregation (DLCA) algorithm to model the silica aerogel morphology [2], other works have looked into the application of ballistic cluster-cluster aggregation (BLCA) algorithms [3] for the same. In this contribution, a hybrid cluster-cluster aggregation (HCA) model is presented to model the silica aerogel microstructure, which provides a directionality bias factor, thus a partial ballistic nature along with the pure Brownian motion. This is critical to understand the influence of ballistic motion on the morphology of the silica aerogel microstructure and its mechanical properties. With regard to the high scaling exponent observed, to understand the effect of the pore-wall structure and the random network connectivity on the scaling mechanical properties, the phenomena are investigated individually simulating compression, once by unit structure with corrugated pore walls (having different particle neck sizes) and the other by a micro structure modeled with HCA model. REFERENCES [1] A. Emmerling, J. Fricke, Journal of Sol-Gel Science and Technology, 8, 781-788, 1997. [2] R. Abdusalamov, C. Scherdel, M. Itskov, B. Milow, G. Reichenauer, Ameya Rege, The Journal of Physical Chemistry B, 125, 1944-1950, 2021. [3] M. Grzegorczyk, M. Rybaczuk, K.Maruszewski, Chaos, Solitons & Fractals, 9(4), 1003-1011, 2004