Abstract

Aerogels are low-density and high-porosity materials that are most commonly prepared by removing the pore liquid from a wet gel with supercritical extraction. The most extensively studied and characterized are silica aerogels, which can be prepared in the density range of 3 to 500 kg/m³ through a proper control of preparative variables. The unusual properties of these materials, such as high surface area and pore volume, low thermal conductivity, and low dielectric constant, make them attractive for applications in diverse areas including thermal insulation, detection of high energy particles, and catalysis. The challenge is to produce them in a cost-competitive process, which means exploring options that do not involve supercritical drying. Recent results show that with surface modification, aerogel-like materials can indeed be produced at ambient conditions. Other ongoing research has been directed at the preparation and characterization of nonsilicate aerogels, as well as organic and inorganic–organic hybrid materials in an attempt to define their properties and to identify potential applications.