Heat treatment customizes pore structure of silica aerogel: The induced role of faults

The pore structure is a critical determinant of the properties of silica aerogels. However, the highly random nature of pore structures and their distribution pose significant challenges for designing the nanostructure of silica aerogels using a bottom-up approach. In this work, we propose utilizing faults in the silica backbone as "initial merging points"to adjust the pore structure of silica aerogels through heat treatment. Additionally, we present an atomic-scale visualization of pore structure evolution across various temperatures using large-scale molecular dynamics simulations (100 ns). Notably, this work is the first to propose anatomic model of the pore structure of silica aerogels. Our findings reveal that minor faults (tensile strain < 20%) have a limited impact on the pore structure, while significant faults (tensile strain > 30%) serve as "initial merging points", driving mass transfer and leading to the minimization of adjacent pores. Furthermore, two distinct types of pore structures were identified in the aerogel before mass transfer. After heat treatment, the specific surface area of silica aerogels with faults was found to increase compared to those without. These results offer valuable insights into the nanostructure design of silica aerogels in 3D technologies.