Particle dynamics and interactions in silica aerogels: An experimental and numerical investigation

Abstract

Silica aerogels are recognised for their intricate microstructure, which has been effectively analysed using various computational techniques. These techniques help in exploring the network formation and subsequent material characterisation of silica aerogels. Such studies complement experimental observations pertaining to the sol-gel process that leads to silica wet-gels, allowing for detailed monitoring of the gelation kinetics at the molecular level.

This thesis builds on established coarse-grained simulation methods based on Langevin dynamics to study the gelation process of silica aerogels. The research focuses on understanding the molecular interactions and synthesis parameters that influence the behaviour of the system. By modelling the gelation kinetics, this study measures the growth in the formation of clusters and radius of gyration to reveal insights into the development of the silica network structure. Furthermore, the impact of sticking probability on the aggregation kinetics and structure is studied, along with a corresponding pair correlation function g(r). The model’s reliability is confirmed through experiments using dynamic light scattering and UV-visible spectroscopy as characterisation techniques. The gelation kinetics is observed with an increasing hydrodynamic radius over time of gelation, and the resulting condensation kinetics curve is obtained from the UV-visible measurements. These techniques offer real-time insights into the aggregation and growth processes, enabling direct comparisons between the experimental data and simulation results. By utilising both computational simulations and experimental approaches, this research aims to identify the key factors that influence the dynamics of silica aerogel formation. The numerical model can also be subsequently extended in future studies to analyse solvent exchange and drying effects on the structure.