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New "crumpled" graphene really doesn't stack up

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October 26, 2011

A crumpled graphene ball created by Northwestern University researchers inspired by a tras...

A crumpled graphene ball created by Northwestern University researchers inspired by a trash can full of crumpled-up papers

We've written a lot about the potential of using graphene in electronics and materials science, but there are challenges when it comes to producing and utilizing these one-atom-thick sheets of carbon on a large scale. While a lack of an internal structure provides graphene with an abundance of surface area, sheets of the material tend to stick together like a stack of paper, resulting in a reduction in surface area and effectiveness. Now, taking inspiration from a trashcan of crumpled-up papers, Northwestern University researchers have developed a new form of graphene that can't be stacked.

Common steps in materials processing, such as heating, solvent washing, compression, and mixing with other materials can see graphene sheets banding together due to a strong interaction between the sheets called the "Van der Waals attraction." Not only does this reduce the amount of original surface area available, stacked graphene sheets also become rigid and lose their processability. Some previous efforts have involved trying to physically keep the sheets apart by inserting non-carbon "spacers", but this changes the chemical composition of the material.

By crumpling graphene sheets into balls, researchers have created a form of graphene that allows the material to remain pure, retaining the same electrical properties and surface area as separate flat sheets, but is more useful for applications that require large amounts of the material.

Lead researcher Jiaxing Huang and his team made the crumpled graphene balls by creating freely suspended water droplets containing graphene-based sheets. Using a carrier gas to blow the aerosol droplets through a furnace, he water quickly evaporated and the thin graphene sheets were compressed by capillary force into near-spherical particles.

"If you imagine a trash can filled with paper crumples, you really get the idea," says Huang. "The balls can stack up into a tight structure. You can crumple them as hard as you want, but their surface area won't be eliminated, unlike face-to-face stacking."

Huang says the resultant crumpled graphene particles are also remarkably stable against mechanical deformation because the ridges formed in the crumpling process make them harder the harder you compress them.

"We expect this to serve as a new graphene platform to investigate application in energy storage and energy conversion," Huang said.

A paper describing the Northwestern University team's findings was published in the October 13 issue of the journal ACS Nano.

About the Author
Darren Quick Darren's love of technology started in primary school with a Nintendo Game & Watch Donkey Kong (still functioning) and a Commodore VIC 20 computer (not still functioning). In high school he upgraded to a 286 PC, and he's been following Moore's law ever since. This love of technology continued through a number of university courses and crappy jobs until 2008, when his interests found a home at Gizmag.   All articles by Darren Quick
4 Comments

Well, that's an interesting development. A material that gets better (for some uses) when it's all crunched up.

I'm more interested in how graphene gets more rigid when stacked. That should have applications in composite materials.

Gregg Eshelman
26th October, 2011 @ 10:20 pm PDT

This has also been explored via simulation:



http://prb.aps.org/abstract/PRB/v84/i20/e205451

johnny_red
22nd November, 2011 @ 04:28 pm PST

I'm thinking that a waffle print of a sheet of graphene would be better. I can't imagine many circumstances where a crumpled ball of graphene would be too usefull.

Ethan Brush
28th January, 2012 @ 12:08 pm PST

One application I can see is the use in composite fabrication where these balls could be used as internal filler to provide stability against buckling /crushing in thin wall tube fabrications.

The real world evidence is in the bone structure of birds where high strength to weight is acheived by a bone structure with internal filaments rather than dense core as in land based animals.

Doug Bowles
29th January, 2012 @ 06:07 pm PST
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