Editing Gel (section)

===Xerogels===

[[File:IUPAC definition for a xerogel.png|550px|thumb|right|alt=IUPAC definition for a xerogel|link=https://doi.org/10.1351/goldbook.X0670|https://doi.org/10.1351/goldbook.X06700.]]

A '''xerogel''' {{IPAc-en|ˈ|z|ɪər|oʊ-|ˌ|dʒ|ɛ|l}} is a solid formed from a gel by drying with unhindered shrinkage. Xerogels usually retain high porosity (15–50%) and enormous surface area (150–900 m<sup>2</sup>/g), along with very small [[Porosity|pore]] size (1–10&nbsp;nm). When [[solvent]] removal occurs under [[supercritical fluid|supercritical]] conditions, the network does not shrink and a highly porous, low-density material known as an ''[[aerogel]]'' is produced. Heat treatment of a xerogel at elevated temperature produces viscous [[sintering]] (shrinkage of the xerogel due to a small amount of viscous flow) which results in a denser and more robust solid, the density and porosity achieved depend on the sintering conditions.