The roles of density and oxygen concentration on the structure of silica aerogel: Insight from an atomistic study

Abstract

The structure of silica aerogels has strong dependence on the density ρ and oxygen concentration. In this study, molecular dynamic simulations are performed to study the roles of ρ and O/Si molar ratio (OSMR) on the structure of silica aerogels. The average pore size and porosity of silica aerogels increase with decreasing ρ. The OSMR influences the structure by changing the forming ability of tenuous ligaments in silica aerogels. The forming ability of tenuous ligaments decreases with decreasing OSMR from 2.0 to 1.9; then increases with further decreasing OSMR to 1.5. The increasing tenuous ligaments in silica aerogel leads to the dispersed ligaments and small average pore size. This study explains the correlation between the ρ, OSMR and the structure of silica aerogel, which can further guide to tune the structure of silica aerogels in experiments.