"Frozen Smoke" May Be Material of Future

By Bijal P. Trivedi
National Geographic Today

May 8, 2002

Stephen Steiner, a sophomore at the University of Wisconsin-Madison, and
three of his classmates just took a wild ride in an airplane nicknamed
"the vomit comet," but they weren't seeking thrills at a local carnival.
Working with NASA, they went weightless to test a new manufacturing
process for aerogel, a high-tech foam that could revolutionize just
about everything from refrigerator design to spacecraft.

"Aerogel is space-age Styrofoam," says Steiner. "As I read about it, I thought that this is really weird, cool stuff with amazing properties and I wondered whether I could make it myself."

Aerogel is pure silicon dioxide, or sand, like glass but a thousand times less dense. The "amazing properties" include being the lightest solid substance ever created, up to 99.5 percent air in tiny pockets called nanopores. If flattened out, a cubic inch would yield a surface area bigger than a football field. Yet what sounds like the stuff of science fiction promises to be incredibly practical. Just a thin panel can shield a hand from a blowtorch flame. Nearly transparent, a one-inch aerogel windowpane could insulate as well as 10 inches (25 centimeters) of conventional glass panes if you didn't mind the slightly blue hue that comes from processing the silica aerogel on Earth.

The material, which has been around since the 1930s, is already being used in space exploration, serving as insulation on the Mars Pathfinder mission and a tennis racket-shaped piece on the Stardust Spacecraft is being used to collect comet particles.

Steiner, now 20, learned about aerogel as a high school student, investigating semiconductors on the Internet. Consulting with Lawrence Berkeley National Laboratory researchers, he modified aerogel production, designed a special oven and succeeded in making a chunk of the ethereal substance, sometimes called "frozen smoke."

"It was very ambitious. I was surprised he was able to do it," says Dr. Arlon Hunt, an aerogel expert at the national laboratory.

The research led to a string of prizes, but Steiner wanted to eliminate the smoky blue hue to make the product more suitable for windows and other applications. The key was the nanopores, which are not much bigger than atoms. When formed on Earth, aerogel contains more large pores that scatter blue and violet light, but if they were even smaller and more uniform, most of the light would pass through whole and clear, researchers believe. Experiments on space shuttle missions in 1998 and 1999 suggested a difference between Earth-made and space-made gels, but the results were inconclusive.

Steiner was convinced aerogel structure would be significantly different if manufactured in space, but to test his theories, he had to escape the Earth's gravity.

"People never consider the role of gravity in chemical reactions," says Steiner, a chemistry major with a penchant for engineering.

In late April, Steiner and his team from Wisconsin's Madison campus traveled to the Johnson Space Center in Houston to board a converted Boeing 707, once the province of only astronauts. As part of the Reduced Gravity Student Flight Program, they tested Steiner's notions on NASA's KC-135A, an aircraft simulating the weightlessness of space in stomach-wrenching zero-gravity maneuvers. Flying a series of steep parabolic arcs, passengers experience weightlessness for about 25 seconds on each arc.

That didn't give Steiner much time. Making the material is a two-step process, beginning with the creation of a Jell-O-like substance called an alcogel, which is later dried in a high-pressure oven to produce aerogel. Air-pocket size is established during the critical alcogel formation, which typically takes several hours.

Steiner devised a rapid gelation process, allowing alcogels to be created in just a few seconds in a semi-automated mini-lab on the KC-135A. He tried out his recipe on the aircraft last year when he was only a freshman, but his equipment wasn't up to the task.

"Our first attempt was very unsuccessful," he admits. "I didn't understand how sophisticated the engineering had to be. The equipment didn't work."

This year, using equipment designed to do the chemistry in zero gravity, he produced two 1.5-inch discs of alcogel, which he will dry in his basement this summer. The two samples won't provide enough for a rigorous scientific analysis, but Steiner is convinced he's on the right track.

"I've been making aerogels a long time and these alcogels are definitely less blue than they would be if made on Earth," he says. "I think it worked."

This story airs on National Geographic Today on May 8 and 9, 2002. National Geographic Today, at 7 pm. ET/PT in the United States (repeating the following day at 9 a.m. and midday ET/PT), is a daily news magazine available only on the National Geographic Channel. Click here to request it.

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