Molecular simulation of silica gels: Formation, dilution, and drying

Abstract

The formation and ageing of gels is a complex issue that has to be resolved to investigate manifold synthetic materials, among them: porous materials such as cement, high-quality glass fiber, and geomaterials for radioactive waste sealing. Herein, a coupling between a grand canonical Monte Carlo and the parallel tempering methods is developed. The gain in simulation time is of, at least, two orders of magnitude; therefore, we are able to move at will on the water to silicon ratio axis and to observe the restructuring of gels during dilution and drying. At high water to silicon ratio, a colloidal-like structure is obtained, mostly constituted of silicate chains. As humidity is an essential aspect of gels, affecting their physical and mechanical properties, the effect of drying is herein investigated. In agreement with experiments, the structure becomes denser, crosslinks between silicate chains increase and glasslike structures are observed locally.