Featured Research

from universities, journals, and other organizations

Graphene's strength lies in its defects

Date:
November 11, 2010
Source:
Brown University
Summary:
Materials engineers have found that the juncture at which graphene sheets meet does not compromise the material's strength. These so-called grain boundaries are so strong, in fact, that the sheets are nearly as strong as pure graphene. The trick lies in the angles at which the individual sheets are stitched together.

Engineers had thought that sheet of graphene that are joined together would have weakneses at the point of attachment. In some cases, however, the area where two sheets of graphene are joined can be as strong as pure graphene. Vivek Shenoy, with graduate student Rassin Grantab, illustrates the carbon heptagons that mark these “grain boundaries.”
Credit: Mike Cohea/Brown University

The website of the Nobel Prize shows a cat resting in a graphene hammock. Although fictitious, the image captures the excitement around graphene, which, at one atom thick, is the among the thinnest and strongest materials ever produced.

A significant obstacle to realizing graphene's potential lies in creating a surface large enough to support a theoretical sleeping cat. For now, material scientists stitch individual graphene sheets together to create sheets that are large enough to investigate possible applications. Just as sewing patches of fabric together may create weaknesses where individual patches meet, defects can weaken the "grain boundaries" where graphene sheets are stitched together -- at least that is what engineers had thought.

Now, engineers at Brown University and the University of Texas-Austin have discovered that the grain boundaries do not compromise the material's strength. The grain boundaries are so strong, in fact, that the sheets are nearly as strong as pure graphene. The trick, they write in a paper published in Science, lies in the angles at which the individual sheets are stitched together.

"When you have more defects, you expect the strength to be compromised," said Vivek Shenoy, professor of engineering and the paper's corresponding author, "but here it is just the opposite."

The finding may propel development of larger graphene sheets for use in electronics, optics and other industries.

Graphene is a two-dimensional surface composed of strongly bonded carbon atoms in a nearly error-free order. The basic unit of this lattice pattern consists of six carbon atoms joined together chemically. When a graphene sheet is joined with another graphene sheet, some of those six-carbon hexagons become seven-carbon bonds -- heptagons. The spots where heptagons occur are called "critical bonds."

The critical bonds, located along the grain boundaries, had been considered the weak links in the material. But when Shenoy and Rassin Grantab, a fifth-year graduate student, analyzed how much strength is lost at the grain boundaries, they learned something different.

"It turns out that these grain boundaries can, in some cases, be as strong as pure graphene," Shenoy said.

The engineers then set out to learn why. Using atomistic calculations, they discovered that tilting the angle at which the sheets meet -- the grain boundaries -- influenced the material's overall strength. The optimal orientation producing the strongest sheets, they report, is 28.7 degrees for sheets with an armchair pattern and 21.7 degrees for sheets with a zigzag layout. These are called large-angle grain boundaries.

Large-angle grain boundaries are stronger because the bonds in the heptagons are closer in length to the bonds naturally found in graphene. That means in large-angle grain boundaries, the bonds in the heptagons are less strained, which helps explain why the material is nearly as strong as pure graphene despite the defects, Shenoy said.

"It's the way the defects are arranged," Shenoy said. "The grain boundary can accommodate the heptagons better. They're more relaxed."

Rodney Ruoff from the University of Texas-Austin's Department of Mechanical Engineering is a contributing author on the paper. The National Science Foundation and the Semiconductor Research Corporation's Nanoelectronics Research Initiative funded the research.


Story Source:

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


Journal Reference:

  1. Rassin Grantab, Vivek B. Shenoy, and Rodney S. Ruoff. Anomalous Strength Characteristics of Tilt Grain Boundaries in Graphene. Science, 12 November 2010 330: 946-948 DOI: 10.1126/science.1196893

Cite This Page:

Brown University. "Graphene's strength lies in its defects." ScienceDaily. ScienceDaily, 11 November 2010. <www.sciencedaily.com/releases/2010/11/101111141814.htm>.
Brown University. (2010, November 11). Graphene's strength lies in its defects. ScienceDaily. Retrieved July 24, 2014 from www.sciencedaily.com/releases/2010/11/101111141814.htm
Brown University. "Graphene's strength lies in its defects." ScienceDaily. www.sciencedaily.com/releases/2010/11/101111141814.htm (accessed July 24, 2014).

Share This




More Matter & Energy News

Thursday, July 24, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Creative Makeovers for Ugly Cellphone Towers

Creative Makeovers for Ugly Cellphone Towers

AP (July 24, 2014) Mobile phone companies and communities across the country are going to new lengths to disguise those unsightly cellphone towers. From a church bell tower to a flagpole, even a pencil, some towers are trying to make a point. (July 24) Video provided by AP
Powered by NewsLook.com
Algonquin Power Goes Activist on Its Target Gas Natural

Algonquin Power Goes Activist on Its Target Gas Natural

TheStreet (July 23, 2014) When The Deal's Amanda Levin exclusively reported that Gas Natural had been talking to potential suitors, the Ohio company responded with a flat denial, claiming its board had not talked to anyone about a possible sale. Lo and behold, Canadian utility Algonquin Power and Utilities not only had approached the company, but it did it three times. Its last offer was for $13 per share as Gas Natural's was trading at a 60-day moving average of about $12.50 per share. Now Algonquin, which has a 4.9% stake in Gas Natural, has taken its case to shareholders, calling on them to back its proposals or, possibly, a change in the target's board. Video provided by TheStreet
Powered by NewsLook.com
Robot Parking Valet Creates Stress-Free Travel

Robot Parking Valet Creates Stress-Free Travel

AP (July 23, 2014) 'Ray' the robotic parking valet at Dusseldorf Airport in Germany lets travelers to avoid the hassle of finding a parking spot before heading to the check-in desk. (July 23) Video provided by AP
Powered by NewsLook.com
Boeing Ups Outlook on 52% Profit Jump

Boeing Ups Outlook on 52% Profit Jump

Reuters - Business Video Online (July 23, 2014) Commercial aircraft deliveries rose seven percent at Boeing, prompting the aerospace company to boost full-year profit guidance- though quarterly revenues missed analyst estimates. Bobbi Rebell reports. Video provided by Reuters
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