Anti-pollution tool is ‘not a pipe dream’
Rice scientists unveil secrets of carbon nanotubes, a fiber that breaks down methane into clean energy
At a lab inside Rice University’s chemistry building, doctoral candidate Oliver Dewey unspools a fiber so fine that trying to catch a glimpse of it can strain the eye.
It’s thinner than a human hair, but when dozens are braided together, it begins to look like a regular strand of charcoal-black thread — so much so that it can be threaded into a sewing machine.
But its size in Rice’s lab disguises its potential. It’s 20 percent stronger than Kevlar, and ounce-for-ounce more than 100 times stronger than steel. It can conduct more electricity than copper and, as researchers at Rice just discovered, can convert heat into electricity. And it’s created by breaking down one of the most harmful greenhouse gases: methane.
Meet the carbon nanotube, a material that has the potential to decarbonize the notoriously dirty metals industry by using natural gas. Matteo Pasquali, a chemical engineer who directs Rice’s Carbon Hub, said the promise of carbon nanotubes led the U.S. Department of Energy to give his institute a $3.3 million grant to find better ways to create it.
“It’s not a pipe dream. This is something a lot of us have been doing for 20-plus years in the nanotech field,” Pasqua
li said. “We already know how to do this, we just don’t know how to do it efficiently.”
The fibers are made by taking methane gas and heating it in the absence of oxygen to 800 to 1,200 degrees Celsius. That forces the methane to crack into pure hydrogen — which could be used as a clean fuel — and carbon nanotube fibers. Lab workers take the carbon nanotube fibers and mix it with chlorosulfonic acid, which turns the tubes into a liquid, and push it through tiny holes poked into a small circular disk.
Out the other end comes tiny, spaghetti-like strands in water, pulled through by a wheel that collects the fibers and spins them onto spools. In essence, it takes one of the most damaging greenhouse gases and turns it into a potential fuel source and a potential substitute for steel and aluminum and copper.
And reducing the need to mine those materials could keep tons of carbon dioxide from entering the atmosphere. As much as 7 percent of global emissions come from mining operations alone, according to McKinsey & Co. Researchers like Pasquali and others envision a day when bridges and transmission lines and buildings use carbon nanotubes mixed with metals, or on their own, as their foundations.
While Pasquali and other researchers have been making the material for decades, creating enough to construct a bridge is only a dream for now.
The Carbon Hub’s lab can only churn out about one gram of the stuff every hour. A handful of companies — including Houstonbased Huntsman Corp. — are trying to make it possible to create vastly larger amounts.
Scott Wright, a division president at Huntsman, said that when his company bought the technology to make carbon nanotubes a few years ago, it was only able to generate a gram an hour. Now, he said, it can make one kilogram an hour, and he expects in the next few years to be able to make thousands of tons of it per year.
Already, he said, his company has sold films of carbon nanotubes that are now being used on NASA’s Juno Satellite that is orbiting Jupiter.
“I think the potential here is enormous,” Wright said. “Think about the basic science of what we're doing: We’re taking a material that is already being vented from oil wells and so on all over the world, capturing that waste gas and turning it into carbon to make structural materials clean.”
The fibers could also
prove to be a source of electricity generation.
Rice University Physicist Junichiro Kono led an effort with scientists at the Tokyo Metropolitan University in which scientists aligned carbon nanotubes as fibers and sewed them into fabrics. Their smallscale test showed about four forearm-sized cloths using the nanotubes were able to convert the heat from two hotplates into enough electricity to power a small LED light.
Scientists and manufacturers are still decades away from maximizing these potential uses, Pasquali said. He likened it to the development of solar panels, which were in use as early as the 1950s in high-tech applications like satellites but didn’t become affordable commercially until decades later.
In the meantime, Dewey, the doctoral candidate, said that adding it to cheaper materials to make them stronger will help bring it to scale.
“It’s rather expensive right now, especially the higher quality stuff,” Dewey said.
“We’re a ways out from making it more commercially viable, but we’re working on it at a time right now when governments and people want to pour money into things like this.”