Free Newsletters - Space - Defense - Environment - Energy - Solar - Nuclear
..
. 24/7 Space News .




CARBON WORLDS
Even with defects, graphene is strongest material in the world
by Staff Writers
New York NY (SPX) Jun 04, 2013


Graphene remains the strongest material ever measured and, as Columbia Engineering Professor James Hone once said, so strong that "it would take an elephant, balanced on a pencil, to break through a sheet of graphene the thickness of Saran Wrap." Credit: Illustration by Andrew Shea for Columbia Engineering.

In a new study, published in Science May 31, 2013, Columbia Engineering researchers demonstrate that graphene, even if stitched together from many small crystalline grains, is almost as strong as graphene in its perfect crystalline form. This work resolves a contradiction between theoretical simulations, which predicted that grain boundaries can be strong, and earlier experiments, which indicated that they were much weaker than the perfect lattice.

Graphene consists of a single atomic layer of carbon, arranged in a honeycomb lattice. "Our first Science paper, in 2008, studied the strength graphene can achieve if it has no defects-its intrinsic strength," says James Hone, professor of mechanical engineering, who led the study with Jeffrey Kysar, professor of mechanical engineering.

"But defect-free, pristine graphene exists only in very small areas. Large-area sheets required for applications must contain many small grains connected at grain boundaries, and it was unclear how strong those grain boundaries were. This, our second Science paper, reports on the strength of large-area graphene films grown using chemical vapor deposition (CVD), and we're excited to say that graphene is back and stronger than ever."

The study verifies that commonly used methods for post-processing CVD-grown graphene weaken grain boundaries, resulting in the extremely low strength seen in previous studies. The Columbia Engineering team developed a new process that prevents any damage of graphene during transfer.

"We substituted a different etchant and were able to create test samples without harming the graphene," notes the paper's lead author, Gwan-Hyoung Lee, a postdoctoral fellow in the Hone lab.

"Our findings clearly correct the mistaken consensus that grain boundaries of graphene are weak. This is great news because graphene offers such a plethora of opportunities both for fundamental scientific research and industrial applications."

In its perfect crystalline form, graphene (a one-atom-thick carbon layer) is the strongest material ever measured, as the Columbia Engineering team reported in Science in 2008-so strong that, as Hone observed, "it would take an elephant, balanced on a pencil, to break through a sheet of graphene the thickness of Saran Wrap."

For the first study, the team obtained small, structurally perfect flakes of graphene by mechanical exfoliation, or mechanical peeling, from a crystal of graphite. But exfoliation is a time-consuming process that will never be practical for any of the many potential applications of graphene that require industrial mass production.

Currently, scientists can grow sheets of graphene as large as a television screen by using chemical vapor deposition (CVD), in which single layers of graphene are grown on copper substrates in a high-temperature furnace. One of the first applications of graphene may be as a conducting layer in flexible displays.

"But CVD graphene is 'stitched' together from many small crystalline grains-like a quilt-at grain boundaries that contain defects in the atomic structure," Kysar explains.

"These grain boundaries can severely limit the strength of large-area graphene if they break much more easily than the perfect crystal lattice, and so there has been intense interest in understanding how strong they can be."

The Columbia Engineering team wanted to discover what was making CVD graphene so weak. In studying the processing techniques used to create their samples for testing, they found that the chemical most commonly used to remove the copper substrate also causes damage to the graphene, severely degrading its strength.

Their experiments demonstrated that CVD graphene with large grains is exactly as strong as exfoliated graphene, showing that its crystal lattice is just as perfect. And, more surprisingly, their experiments also showed that CVD graphene with small grains, even when tested right at a grain boundary, is about 90% as strong as the ideal crystal.

"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. "This strength will be invaluable as scientists continue to develop new flexible electronics and ultrastrong composite materials."

Strong, large-area graphene can be used for a wide variety of applications such as flexible electronics and strengthening components-potentially, a television screen that rolls up like a poster or ultrastrong composites that could replace carbon fiber.

Or, the researchers speculate, a science fiction idea of a space elevator that could connect an orbiting satellite to Earth by a long cord that might consist of sheets of CVD graphene, since graphene (and its cousin material, carbon nanotubes) is the only material with the high strength-to-weight ratio required for this kind of hypothetical application.

The team is also excited about studying 2D materials like graphene. "Very little is known about the effects of grain boundaries in 2D materials," Kysar adds.

"Our work shows that grain boundaries in 2D materials can be much more sensitive to processing than in 3D materials. This is due to all the atoms in graphene being surface atoms, so surface damage that would normally not degrade the strength of 3D materials can completely destroy the strength of 2D materials.

"However with appropriate processing that avoids surface damage, grain boundaries in 2D materials, especially graphene, can be nearly as strong as the perfect, defect-free structure."

.


Related Links
Columbia University
Carbon Worlds - where graphite, diamond, amorphous, fullerenes meet






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News





CARBON WORLDS
Climate: Carbon 'offsets' rise 4% in 2012
Paris (AFP) May 30, 2013
Trade in carbon offsets, a voluntary means of reducing one's footprint in global-warming gases, rose by four percent in volume terms last year as the market price of carbon collapsed, a report said on Thursday. Voluntary commitments for offsets for immediate or future delivery reached 101 million tonnes of carbon dioxide or its equivalent (CO2e) after 97 million tonnes CO2e in 2011, Ecosyste ... read more


CARBON WORLDS
NASA's GRAIL Mission Solves Mystery of Moon's Surface Gravity

Moon dust samples missing for 40 years found in Calif. warehouse

Unusual minerals in moon craters may have been delivered from space

Moon being pushed away from Earth faster than ever

CARBON WORLDS
Mars Curiosity Rover Provides Strong Evidence for Flowing Water

Ten Years At Mars: New Global Views Plot History Of The Red Planet

Flowing Water Transported Sand, Rocks Along Martian Streambed

Leicester Scientist Helps Discover Ancient Streambed On Mars

CARBON WORLDS
White House moves to curb 'patent trolls'

A certain level of stress is necessary

Northrop Grumman-Built Modular Space Vehicle Nears Completion of Manufacturing Phase

French government posts space counsellor in Bangalore

CARBON WORLDS
Shenzhou-10 spacecraft to be launched in mid-June

Sizing Up Shenzhou 10

Rollout for Shenzhou 10

Soft Pedal for Shenzhou 10

CARBON WORLDS
International trio takes shortcut to space station

Science and Maintenance for Station Crew, New Crew Members Prep for Launch

ESA Euronews: Living in space

Next destination: space

CARBON WORLDS
The Future of Space Launch

Rocket Engine Maker Proton-PM to Invest in New Products

Russia Launches European Telecoms Satellite

Ariane poised to launch first 20 ton payload into orbit

CARBON WORLDS
Rare Stellar Alignment Offers Opportunity To Hunt For Planets

In feat, telescope directly spots lightweight exoplanet

Scouting for Not-So-Distant Worlds

Lightest exoplanet imaged so far?

CARBON WORLDS
Atom by atom, bond by bond, a chemical reaction caught in the act

Dense hydrogen in a new light

Another American High Frontier First: 3-D Manufacturing in Space

Charred micro-bunny sculpture shows promise of new material for 3-D shaping




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement