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Airgel is a silica-based substance that holds 15 Guinness World Records for properties such as being the lowest density solid and the best insulator. It is made by removing liquid from a silica alcogel and replacing it with air. Airgel is expensive due to the manufacturing process, but its potential applications are vast. It has been used by NASA and could be used for insulation in homes or new forms of artwork.
Airgel is an advanced material that holds 15 entries in the Guinness Book of World Records for properties such as the lowest density solid and the best insulator. It is a silica-based substance, made up of a loose dendritic network of the silicon atom. Airgel is made by gently removing the liquid, usually ethanol, from a silica alcogel, replacing it with nothing but air, which makes up 99.8% of the final product. Some aerogels have a density of as little as 001 grams per cubic centimeter (0005 ounces per cubic inch).
The tactile feel of airgel is like that of hard plastic foam. Its physical appearance is semi-transparent like that of solidified mist, earning it the nickname “frozen smoke”. Airgel breaks down easily, making it unsuitable as a self-contained window insulator, but it can support up to 2000 times its own weight. It’s very expensive due to the chemicals and processes behind its manufacture, costing up to $300 per cubic inch (2.54 cubic centimeters), though prices are coming down. There are several varieties of airgel, with slightly different colors and strengths, based on variations in the manufacturing process.
Airgel was created by Steven Kistler in 1931, but its applications weren’t really realized until the 1960s and 1970s. The 1980s saw a resurgence in the aerogel field, with top-notch institutions like NASA and Berkeley Labs working on field research. They have been considered as a replacement for polyurethane foam in refrigerators and as an insulator for windows. Airgel has been used on NASA space missions to capture micrometeorite particles for study without damaging their structure.
Airgel is made by releasing all of the water from a colloidal silica gel without disturbing its overall structure. When gels quench at normal temperatures and pressures, surface tension in the tiny pores of the gel causes the structure to shrink and shrink to about 10 times its original volume. In aerogel production, a gel is placed in a vessel at a high temperature (280°C or 536°F) and pressure (1800 pounds per square inch, or 1241 Newtons per square centimeter). This causes the liquid within the gel to enter a supercritical state, allowing for a liquid-to-gas phase transition without the related shrinkage that causes a fine structure of the gel to collapse. This process is known as supercritical drying. The process originally took days to create aerogels, but improvements have compressed the drying time to a few hours. The process is still energy hungry, leading to the high cost of aerogels.
Aerogels truly qualify as a “space age material,” an advanced arrangement of matter with no analogues in nature. It could one day be used in a wide range of applications, from insulation for homes to new forms of artwork. Many young researchers focus on this, mixing airgel with additives such as carbon to increase its insulating properties or working to minimize pore size to make the airgel as transparent as possible. There are many directions for future research and many potential applications if this research bears fruit.
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