Tiny `tubes' and big dreams

Nanotubes: Highly talented carbon molecules could be a profitable business if they can be tamed.

Medicine & Science

May 10, 2004|By Frank D. Roylance | Frank D. Roylance,SUN STAFF

Like the old Seinfeld show, the story of nanotubes is a story about nothing. Or nearly nothing.

To the naked eye, a vial of nanotubes looks like a fine black powder, the sort of stuff you can wipe off the disks of your car's brakes. "It's basically soot," said Peter J. Burke, a researcher at the University of California at Irvine.

In fact, nanotubes are tiny carbon molecules with astonishing strength and lightness, electrical conductivity, heat conductivity and sharpness.

Since nanotubes were discovered in 1991, their boosters have promised a revolution in products, including high-strength aircraft parts, faster computers, more powerful batteries, cheaper and more efficient video displays and lights, better fuel cells and disposable chemical and biological sensors.

"We believe that this material we produce is going to be touching most of our lives," said Ray McLaughlin, executive vice president of Carbon Nanotechnologies Inc. in Houston.

"Once we perfect the manufacturing side of it, and the world starts to figure out how to use it, it's going to be very powerful. ... We're betting our whole lives on it."

But manufacturing carbon nanotubes has proved to be an enormous challenge. So far, there are no railroad cars on the siding in Houston waiting to load up.

Carbon Nanotechologies is probably the world's leading producer of carbon nanotubes. But the company's current capacity is 20 pounds a day, all for customers' research and development needs.

"We expect to have 100 pounds per day capacity available by midyear," McLaughlin said. "Then we expect to be able to ramp up to fit whatever the demand schedule dictates. And we're expecting sometime in 2005 or 2006 that could be 1,000 to 5,000 pounds a day.

"We are on the verge of some commercial contracts," he said.

Prices for nanotubes have fallen as engineers have inched closer to solving their manufacturing problems. They're now comparable, pound-for-pound, with gold.

Carbon nanotubes are made from nearly nothing.

"Natural gas or carbon monoxide," McLaughlin said. "You heat it up and introduce some catalyst and say a little prayer and end up with some nanotubes. Heat, pressure and catalyst."

The alchemy produces self-assembling hexagonal carbon molecules. They form a sheet of hexagons, one atom thick, that looks like chicken wire.

The carbon sheets roll into seamless tubes 10 or 20 atoms around, and thousands or tens of thousands of times longer than their diameter. They're capped at each end by a half-sphere of carbon hexagons.

("Nano" means these tubes have diameters measured in billionths of a meter; tens of thousands of them would equal a human hair.)

Their lattice-like construction and their chemistry make nanotubes incredibly strong.

"The carbon-carbon bond is one of the strongest chemical bonds in the universe," said Burke, the UC Irvine researcher. "If you think about a diamond, it is just a pure crystal of carbon and extremely strong. A carbon nanotube is a like a pure wire of carbon. So it's a lot smaller, but it still has the same strength."

Carbon nanotubes are stronger than steel. Mixed into a slurry and spun into a fiber, they could yield the lightest, strongest materials known to man. They would add strength and subtract weight from aircraft parts, body armor or even concrete highways.

But nanotubes are still too expensive for high-volume applications, said Thomas A. Weber, materials research director at the National Science Foundation: "Until they get the manufacturing process down, it's going to remain that way."

The problems are formidable. For example, nanotubes form in a random tangle of mixed lengths and diameters. Some have single walls, while others form with multiple walls, like small pipes inside larger pipes.

Manufacturers need to produce the more highly valued single-walled nanotubes more consistently and efficiently. Or, they need an easy way to sort them.

"It looked like an intractable problem," said physicist Michael S. Fuhrer, of the University of Maryland's Center for Superconductivity Research. "Now ... there's initial results saying it's already being done, and it's just going to get better."

Some things are being made with nanotubes. General Motors puts a low-grade form of mixed nanotubes into plastic auto body parts. Their electrical conductivity makes paint stick better. But that's nearly nothing, compared with the nanotube-makers' dreams.

Their highest hopes rest with electronics. The long carbon tubes become raceways for electrons, making nanotubes extraordinary electrical conductors. With a slight twist to the alignment of their molecules, nanotubes become semiconductors.

Conductive nanotubes could lead to lighter and more powerful batteries for portable electronics. Vastly more efficient power transmission cables would make electrical generation cleaner and cheaper.

Since 1998, scientists have experimented with semiconducting nanotube "wires" to make transistors, the fundamental component of computer processing chips.

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