Striving to make almost nothing at all.

Striving to make almost nothing at all

To the uninitiated, an aerogel might took like nothing more than a milky bluish tinge inside an empty glass vial. These nearly transparent, ultralow-density materials, also known as frozen or solid smoke, have been turning the heads of fusion researchers, particle physicists, space scientists and others in need of the next best thing to nothing at all.

The near-nothingness of aerogels makes them well suited for collecting speeding micrometeorites without shattering the samples, says materials scientist John F. Poco of the Lawrence Livermore (Calif.) National Laboratory. Instead of stopping a zippy micrometeorite on a dime, a series of increasingly dense aerogel layers would gradually bring it to rest and thereby improve its chances of remaining intact. Poco says an aerogel "mit" for catching micrometeorites is slated for a future shuttle trip.

Since aerogels contain so little solid material, fusion researchers are using them as unobtrusive holders for fusion fuels, says Lawrence W. Hrubesh, who leads the Livermore lab's effort to make ever-more-wispy aerogels. Aerogels donht dilute laser light or other forms of energy used to ignite fusion fuels.

Even sculptors have started using the ethereal materials as a sub-featherweight medium, and window manufacturers are considering placing them between windowpanes as a nearly transparent insulation, Hrubesh notes.

The Livermore researchers make their aerogels -- which Hrubesh calls the world's airiest -- by chemically transforming tetrahedron-shaped tetramethoxysilane (TMOS) molecules into a dense oil. Then, by reacting the oil with water in the presence of a diluting liquid that serves as temporary wadding to keep the TMOS molecules apart, the scientists link the molecules into delicate networks that surround the liquid wadding. Removing the liquid leaves behind the ultralowdensity skeleton. By varying the amount of diluting liquid, the researchers can make aerogels with predetermined densities ranging from 3 to 800 milligrams per cubic centimeter. Air weighs in at about 1.2 mg/cc.