Morphological changes of silica aged under environmental conditions by three-dimensional nanoscale quantifications

Abstract

In recent decades, nanostructured silica has become a key component in several materials developed at the industrial length scale. Used for its outstanding ability to structure food, drugs, and rubber, to fulfil specific needs in numerous applications, it has also led to the widespread development of sustainable energy-based materials. Superinsulation materials endowed with an exceptionally low thermal conductivity are a major goal regarding energy consumption and carbon dioxide emission. However, because the properties of insulation materials greatly depend on their nanostructures, it is crucial to ensure their hygrothermal stability, by limiting ageing phenomena. Here, we thoroughly characterize the hygrothermal ageing of a fractal industrially relevant silica using a complementary set of experimental techniques, providing local (TEM and electron tomography) and statistical indicators of structural evolution. For the first time, we unambiguously evidence the smoothing of elementary particles and quantify their growth (from 4.3 to 10.0 nm), which results in the densification of aggregates at the upper length scale.