Featured Research

from universities, journals, and other organizations

Graphene rips follow rules

Date:
January 7, 2012
Source:
Rice University
Summary:
Researchers may give science and industry a new way to manipulate graphene, which naturally rips along armchair and zigzag paths.

Under stress, graphene will rip along paths that leave armchair or zigzag edges. Both types of edge favorable for particular electronic applications.
Credit: Vasilii Artyukhov/Rice University

Research from Rice University and the University of California at Berkeley may give science and industry a new way to manipulate graphene, the wonder material expected to play a role in advanced electronic, mechanical and thermal applications.

When graphene -- a one-atom thick sheet of carbon -- rips under stress, it does so in a unique way that puzzled scientists who first observed the phenomenon. Instead of tearing randomly like a piece of paper would, it seeks the path of least resistance and creates new edges that give the material desirable qualities.

Because graphene's edges determine its electrical properties, finding a way to control them will be significant, said Boris Yakobson, Rice's Karl F. Hasselmann Professor of Mechanical Engineering and Materials Science and professor of chemistry.

It's rare that Yakobson's work as a theoretical physicist appears in the same paper with experimental evidence, but the recent submission in Nano Letters titled "Ripping Graphene: Preferred Directions" is a notable exception, he said.

Yakobson and Vasilii Artyukhov, a postdoctoral researcher at Rice, recreated in computer simulations the kind of ripping observed through an electron microscope by researchers at Berkeley.

The California team noticed that cracks in flakes of graphene followed armchair or zigzag configurations, terms that refer to the shape of the edges created. It seemed that molecular forces were dictating how graphene handles stress.

Those forces are robust. Carbon-carbon bonds are the strongest known to man. But the importance of this research, Yakobson said, lies in the nature of the edge that results from the rip. The edge of a sheet of graphene gives it particular qualities, especially in the way it handles electric current. Graphene is so conductive that current flows straight through without impediment -- until it reaches the edge. What the current finds there makes a big difference, he said, in whether it stops in its tracks or flows to an electrode or another sheet of graphene.

"Edge energy" in graphene and carbon nanotubes has long been of interest to Yakobson, who issued a paper last year with a formula to define the energy of a piece of graphene cut at any angle. In molecular carbon, armchair and zigzag edges are the most desirable because atoms along the edge are spaced at regular intervals and their electrical properties are well-known: Zigzag graphene is metallic, and armchair graphene is semiconducting. Figuring out how to rip graphene for nanoribbons with edges that are all one type or the other would be a breakthrough for manufacturers.

Yakobson and his team determined that graphene seeks the most energy-efficient path. The Berkeley team noticed that multiple cracks in a flake of graphene flowed strictly along lines that were at (or at multiples of) 30 degrees apart from each other.

"Graphene prefers to tear by expending the least amount of energy," Yakobson said. He noted the 30-degree separation between the angles that differentiate zigzag and armchair in a hexagonal graphene lattice.

To prove it, Artyukhov spent two months building molecular simulations that pulled virtual scraps of graphene apart in various ways. Depending on the force applied, a flake would rip along a straight line or fork in two directions. But the edges produced would always be along 30-degree lines and would be either zigzag or armchair.

"Basically, the direction of the crack in classical fracture theory is determined by the path it could take with the minimal cost in energy," Artyukhov said. "My simulations showed that under some conditions, this could be the case with graphene. It provided a pretty reasonable and clear and solid explanation for this unusual experimental thing."

Artyukhov found that pulling too hard on virtual graphene would shatter it. "Our main effort was to pull on it delicately enough that it has time to pick the direction it would prefer, rather than have a complete failure." He noted the simulations were much faster than rips that would happen in real-world circumstances.

Also surprising was the discovery that rips in graphene across grain boundaries follow the same rules. Tears do not follow the boundary, which would create energetically unfavorable edges, but pass through and switch to the most favorable direction in the new grain.

"The Berkeley folks didn't do controllable tears, but their work opens technological possibilities for the future," Yakobson said. "For electronics, you want ribbons that go in a particular direction, and this research suggests that this is possible. It would be a big deal.

"Think of graphene like a sheet of postage stamps: You apply a load, and you can tear the sheet in a well-defined direction. That's basically what this experiment reveals for graphene," he said. "There are invisible directions prepared for you."

Co-authors are Rice graduate student Yuanyue Liu as well as graduate students Kwanpyo Kim and William Regan and Professors Michael Crommie and Alex Zettl, all of the University of California at Berkeley.

The research was supported by the Department of Energy, the National Science Foundation and the Office of Naval Research (MURI) and by the Lockheed Martin Corp. through LANCER.


Story Source:

The above story is based on materials provided by Rice University. Note: Materials may be edited for content and length.


Journal Reference:

  1. Kwanpyo Kim, Vasilii I. Artyukhov, William Regan, Yuanyue Liu, M. F. Crommie, Boris I. Yakobson, A. Zettl. Ripping Graphene: Preferred Directions. Nano Letters, 2011; 111215115726002 DOI: 10.1021/nl203547z

Cite This Page:

Rice University. "Graphene rips follow rules." ScienceDaily. ScienceDaily, 7 January 2012. <www.sciencedaily.com/releases/2012/01/120105145710.htm>.
Rice University. (2012, January 7). Graphene rips follow rules. ScienceDaily. Retrieved April 24, 2014 from www.sciencedaily.com/releases/2012/01/120105145710.htm
Rice University. "Graphene rips follow rules." ScienceDaily. www.sciencedaily.com/releases/2012/01/120105145710.htm (accessed April 24, 2014).

Share This



More Matter & Energy News

Thursday, April 24, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

UN Joint Mission Starts Removing Landmines in Cyprus

UN Joint Mission Starts Removing Landmines in Cyprus

AFP (Apr. 23, 2014) The UN mission in Cyprus (UNFICYP) led a mine clearance demonstration on Wednesday in the UN-controlled buffer zone where demining operations are being conducted near the Cypriot village of Mammari. Duration: 01:00 Video provided by AFP
Powered by NewsLook.com
Air Force: $4.2B Saved from Grounding A-10s

Air Force: $4.2B Saved from Grounding A-10s

AP (Apr. 23, 2014) Speaking about the future of the United States Air Force, Chief of Staff Gen. Mark Welsh says the choice to divest the A-10 fleet was logical and least impactful. (April 23) Video provided by AP
Powered by NewsLook.com
Jets Fuel Jump in Boeing's Revenue

Jets Fuel Jump in Boeing's Revenue

Reuters - Business Video Online (Apr. 23, 2014) A sharp rise in revenue for commercial jets offset a decline in Boeing's defense business. And a big increase in deliveries lifted profitability. Fred Katayama reports. Video provided by Reuters
Powered by NewsLook.com
Is North Korea Planning Nuclear Test #4?

Is North Korea Planning Nuclear Test #4?

Newsy (Apr. 22, 2014) South Korean officials say North Korea is preparing to conduct another nuclear test, but is Pyongyang just bluffing this time? Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins