aerogele

Aerogele are ultralight, highly porous solid materials derived from gels in which the liquid component has been replaced with a gas. This process preserves a network of nanoscale pores, producing extremely low density, high porosity, and a large internal surface area. Silica aerogels are the most common, but aerogele can be formed from carbon, metal oxides, polymers, or composites.

Production typically begins with a sol-gel reaction to form a wet gel, followed by drying that removes the liquid without collapsing the pore structure. Supercritical drying is common, though ambient-pressure drying with surface modification is also used to reduce cost.

Properties include very low density (often a few milligrams per cubic centimeter), porosity above 90%, and very low thermal conductivity for solid materials (about 0.013–0.020 W/m·K for silica forms at room temperature). Many aerogele are optically transparent, while others are opaque. They tend to be mechanically fragile, though reinforcement and composite approaches improve toughness.

Applications span thermal insulation for buildings, pipes, spacecraft, and cryogenic systems; daylighting and skylights using translucent forms; acoustic insulation; catalyst supports and adsorbents; energy storage electrodes; sensors; drug delivery; and filtration.

Historically, aerogels were first produced in the 1930s by Samuel S. Kistler, who developed a process to dry gels without collapse. Since then, researchers have developed a wide range of aerogele, including carbon, alumina, and polymer variants, as well as reinforcing composites.

Limitations include cost, brittleness, and moisture sensitivity in hydrophilic forms; ongoing research aims to improve mechanical strength, moisture resistance, and scalable production.