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Even when stitched together, graphene remains the strongest known material

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June 3, 2013

Columbia University researchers have come up with a way to produce large joined sheets of ...

Columbia University researchers have come up with a way to produce large joined sheets of graphene which are just as strong as the material in its pure, crystalline form (Image: Shutterstock)

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A study conducted at Columbia University has revealed that even when stitched together from much smaller fragments, large sheets of graphene still retain much of their mechanical properties. The discovery may be a crucial step forward in the mass-production of carbon nanotubes that could be used to manufacture flexible electronics, ultra-light and strong materials, and perhaps even the first space elevator.

Graphene, the wonder-material

As Prof. Hone at Columbia put it, 'it would take an elephant balanced on a pencil to break...
As Prof. Hone at Columbia put it, "it would take an elephant balanced on a pencil to break through a sheet of graphene the thickness of Saran Wrap" (Picture: Andrew Shea/Columbia Engineering)

In its purest form, graphene is quite remarkable: it is the strongest material known to man, a great conductor of heat and electricity, and is both very stiff and very ductile. Graphene is also exquisitely light: at a mere 0.77 mg per square meter, a giant sheet covering the whole of the Unites States would weigh less than four space shuttles at launch.

Graphene derives the bulk of its strength from two factors. Firstly, each carbon atom is surrounded by six others in a highly stable honeycomb structure, with the atoms locked firmly in place by very strong covalent bonds; secondly, its extremely simple, two-dimensional structure leaves little room for weakening defects to appear in the lattice.

Researchers see in graphene a promising avenue to flexible electronics technology, leading to smart clothing, Harry Potter-style newspapers that can play videos on demand, and smartphones that unfold into full-sized tablets, to name a few. Graphene could also create high-performance composites to replace carbon fiber or, some researchers speculate, even a space elevator that could tether an artificial satellite to Earth (carbon nanotubes, which are rolled-up sheets of graphene, are the only known material with a strength-to-weight ratio high enough to pull off such a feat.)

Toward flexible displays

The latest research may pave the way for flexible electronic devices (Image: Shutterstock)...

Scientists can manufacture very small quantities of pure graphene by mechanically peeling a graphite crystal. The process is adequate for the purposes of research, but it's also very costly and unpractical, so it can't be scaled up for mass production.

To create larger sheets of graphene (about as large as a TV screen), scientists rely instead on a procedure named "chemical vapor deposition" (CVD), in which single layers of graphene are grown inside a high-temperature furnace. The result isn't a uniform structure, but rather resembles a quilt made of small patches (grains) of graphene "sewn" over a thin layer of copper.

Theory dictates that CVD graphene sheets should retain nearly all the strength of their purest counterpart but, in past experiments, they have proven significantly weaker. Columbia University researchers James Hone and Jeffrey Kysar set out to find why, and discovered that what weakens the CVD graphene aren't the grains themselves, but rather the chemical used to remove the copper substrate after the grains have formed.

The team then developed a new process that uses a different etchant to remove the copper substrate, leaving the sheet undamaged. By doing so, they were able to create sheets of graphene that were just as strong as the material in its original, crystalline form.

When the sheet contained large grains, CVD graphene built in this matter tested exactly as strong as its purer, crystalline version; and, more surprisingly, even when the grains were much smaller the material still retained up to 90 percent of its original strength.

"This is an exciting result for the future of graphene, because it provides experimental evidence that the exceptional strength it possesses at the atomic scale can persist all the way up to samples inches or more in size," says Hone.

The researchers will now focus on studying other two-dimensional materials and how they are affected by the presence of grains. "Our work shows that grain boundaries in 2D materials can be much more sensitive to processing than in 3D materials," says Kisar. "This is because all the atoms in graphene are surface atoms, so surface damage can completely destroy the strength of these materials. However with appropriate processing that avoids surface damage, grain boundaries in 2D materials can be nearly as strong as the perfect, defect-free structure."

The study was published in a recent issue of Science.

Sources: Columbia University, Science podcast, Caltech

About the Author
Dario Borghino Dario studied software engineering at the Polytechnic University of Turin. When he isn't writing for Gizmag he is usually traveling the world on a whim, working on an AI-guided automated trading system, or chasing his dream to become the next European thumbwrestling champion.   All articles by Dario Borghino
10 Comments

Did you pull out the bit about a space elevator from just past knowledge? Or, is this showing that it really is more than just a theoretical possibility? Whatever the case, nanoengineering is the future of all industry.

Alex Lekander
3rd June, 2013 @ 03:16 pm PDT

Anyone, I mean...ANYONE have an device that uses ANY Graphene in it?

No. So why ?

Just a bunch of talk. Pure BS. I've been reading about the wonders of Graphene for years now....still not ONE product is out..LOL

Brian Mcc
3rd June, 2013 @ 08:29 pm PDT

#Brian,

I would try not to be so cynical. People said the same thing about aircraft, personal computers, phones, and radios when they were first conceived. Graphene has huge potential, and as the entire article mentions, there are a number of manufacturing challenges to overcome before it can become mainstream. They have just solved a huge one, according to this article.

Smitty777
4th June, 2013 @ 06:16 am PDT

Brian: Since I was a small child ClueLessPeople routinely referred to Lasers as a solution in search of a Problem. This continued for years even as Lasers enabled one innovation after another. Also ClueLessPeople still dismiss LEDs for lighting. However, for at least twenty years most traffic lights have been LEDs with 3M lenses because of the very long service life and rapid switching. General lighting from LEDs is rapidly becoming better, cheaper, and more durable.

Complex innovation takes time to develop before it appears to have almost arrived overnight.

StWils
4th June, 2013 @ 11:08 am PDT

I agree with Smitty. Too many "Couch-Scientists" out there criticizing the superb efforts of those who are bringing the future to us. It used to be that we wouldn't hear about such developments while they were taking place but only discover them when they went to market. Superglue and Velcro for example. But these days thanks to the Internet we get to see the technology in its development stage.

Patience people, the Scientists will have the last laugh over the naysayers!

warren52nz
4th June, 2013 @ 02:04 pm PDT

Graphene toxicity

Graphene stymies body's efforts to expel it. Graphene nanoplatelets can penetrate deeper into the lungs than their size would suggest, say UK researchers. And once there, the body's natural defences cannot deal with them effectively. Chronic exposure could therefore lead to inflammation and disease in a similar way to asbestos fibres.

http://www.rsc.org/chemistryworld/News/2012/February/graphene-inhaled-lungs.asp

ezeflyer
4th June, 2013 @ 02:06 pm PDT

If we are ever going to escape earth, an orbiting city is the first step. And a space elevator is the first step to building the city. The elevator has been technologically impossible. Graphene looks like a step in the direction to developing a building material strong enough.

All higher life on earth has been killed three or four times. It can happen again with little warning. Survival of the species requires expansion to space and other planets. The more expansion, the better our chances of avoiding extinction. If we stay, we become extinct. It's only a matter of time.

Don Duncan
4th June, 2013 @ 07:30 pm PDT

How can people escape Earth? There is no possible way. Not as humans, anyway. The only place in the Universe for us to exist, as a matter of fact, is on Earth. We would have to change our physical form if we want to live somewhere else.

In the meantime, even if all higher life on Earth had been wiped out in the past, that doesn't mean Humanity is doomed to the same fate - we are developing the technology to watch out for the hazard and take steps to mitigate it.

Earth has millions of years left, we should have a relatively easy time managing it until the end of the Sun. The only real problem with Earth is that it is now too small for our aspirations.

Anywhere you look in the Solar system, you'll find that grass grows greenest right here on Earth, ha ha. :)

Grunchy
11th June, 2013 @ 03:53 pm PDT

@Brian Mcc:

"Anyone, I mean...ANYONE have an device that uses ANY Graphene in it?

No. So why ?

Just a bunch of talk. Pure BS."

Google the invention of the Transistor. Now, tell me how long it was until the first transistor radio.

Google the invention of FM. Now tell me how long it was until we switched from AM to FM.

William Carr
13th June, 2013 @ 05:34 pm PDT

@Grunchy

First off, your point is countered by the mere existence of the International Space Station.

www.youtube.com/watch?v=KaOC9danxNo

If chillaxing in your off hours, singing Bowie songs, and becoming an internet celebrity as a result doesn't count as living, I don't know what does. ;)

@Alex Lekander

It actually is more than just a theoretical possibility. This article caught my eye because I actually work for LiftPort, a company working on developing the space space elevator. Currently, our timeline for completion for the Lunar Space Elevator is 2020 (7 years from now), and the Earth Elevator done by 2030 (17 years from now). Graphene is one of three materials that are actually strong enough for the ribbon. The problem was (and I emphasis *was*) getting one of those three technologies to be able to scale up well. Thanks to this discovery, we now have one that scales up well. All the tech to make the space elevator officially exists, now its just a matter of industry and infrastructure building.

@Don Duncan Couldn't agree with you more.

@ezeflyer That's specifically if you have tiny sheets of it to be absorbed. Graphene naturally occurs in pencil lead, and the whole reason people switched to pencil lead was to avoid the toxicity of actual lead. The problem with tiny graphene sheets is as much of a problem of if you have ultra-fine diamond dust vs diamonds in a ring. Just because you have a larger thing around doesn't mean the smaller thing is around to cause its problems.

@Brian Mcc

I have.

starfyredragon
21st June, 2013 @ 09:05 pm PDT
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