First Prize for Weird; A bizarre substance, like 'frozen smoke,' may clean up rivers, run cell phones and power spaceships.(aerogels)

Byline: Mary Carmichael

God, as the hymn goes, may have made all things bright and beautiful, but for sheer weirdness first prize should go to a man-made creation instead: aerogel. A solid that's up to 99 percent gas, it is rigid to a light touch, soft to a stronger one, and shatters like glass if it's put under too much pressure too quickly; it's one of the most enigmatic of materials, as well as one of the most versatile.

It can withstand the heat of a direct flame; engineers use it for insulation on oil rigs and for warmth in the insoles of hiking boots worn in the coldest temperatures on Earth. NASA uses it to trap comet dust blowing through the universe at six kilometers per second. It even works as casual, sporty jewelry--AeroGem sells a key chain with an aerogel bob on the end, and a pendant "hermetically sealed inside silver-over-titanium end caps for added strength and long-lasting, waterproof durability."

The most recent headlines about aerogels, however, don't have anything to do with oil rigs or NASA or geeky jewelry. They instead bring the unfamiliar and exotic materials into practical, and not at all weird, territory, by suggesting a big, broad-reaching new use for them: to clean up pollution. Researchers announced recently in the journal Science that they had created a new form of aerogel capable of sopping up heavy metals, particularly mercury. It could eventually be used to purify contaminated water. There are efforts to make all sorts of new products from the stuff: rocket fuels, catalytic converters for cars, cell-phone batteries. Aerogels may be weird science, but they're turning out to be more practical than they look.

Nicknamed "frozen smoke" after its ethereal appearance, aerogel is neither frozen nor smoke. It's also surprisingly low tech--it's been known since 1931, when lore has it that chemist Steven Kistler discovered it after a colleague bet him that he could not easily take all the liquid out of a gel and replace it with a gas. Kistler heated the gel, forcing out all the liquid, and then replaced it with a gas, methanol. He published the result, his oddly behaving "aerojelly," in Nature that year. Researchers played with his formula for the next seven decades, finally settling on more suitable and safe ingredients for making the stuff: oxides, such as silicon dioxide and aluminum oxide, as the base gel, and carbon dioxide gas in place of highly flammable methanol.

Together, these ingredients can form a structure that chemically resembles glass ...