Sintering of aerogels for glass synthesis

Silica glasses can be synthesized by sintering silica aerogels at temperatures ranging from 900 to 1200 °C, i.e., close to half the temperatures used for glass melting. The heat treatment can be tailored to obtain either fully densified or porous glass. This paper describes the different steps of the transformation of aerogels into glass along with the textural and microstructural transformations. Different types of information are analyzed: variations in dimensional shrinkage and the apparent density as a function of the densification conditions (temperature, duration of the thermal treatment), the associated structural changes, and the changes in the porous characteristics (macro and meso porosity, average pore radius). The kinetics of dimensional shrinkage help characterize the sintering mechanism. Structural data and porous characteristics allowed us to quantify the transformation of internal aggregates and porosity.