Xerogel

Overview
A xerogel ['z I rə,dεl] is a solid formed from a gel by drying with unhindered shrinkage. Gelatin is one example. Xerogel usually retains high porosity (25%) and enormous surface area (150-900 m2/g), along with very small pore size (1-10 nm). When solvent removal occurs under hypercritical (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) and effectively transforms the porous gel into a dense glass.