Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Graphene is strong, but is it tough?

05.02.2016

Berkeley Lab scientists find that polycrystalline graphene is not very resistant to fracture

Graphene, a material consisting of a single layer of carbon atoms, has been touted as the strongest material known to exist, 200 times stronger than steel, lighter than paper, and with extraordinary mechanical and electrical properties. But can it live up to its promise?


Polycrystalline graphene contains inherent nanoscale line and point defects that lead to significant statistical fluctuations in toughness and strength.

Credit: Berkeley Lab

Scientists at the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) have developed the first known statistical theory for the toughness of polycrystalline graphene, which is made with chemical vapor deposition, and found that it is indeed strong (albeit not quite as strong as pristine monocrystalline graphene), but more importantly, its toughness--or resistance to fracture--is quite low. Their study, "Toughness and strength of nanocyrstalline graphene," was published recently in Nature Communications.

"This material certainly has very high strength, but it has particularly low toughness--lower than diamond and a little higher than pure graphite," said Berkeley Lab scientist Robert Ritchie. "Its extremely high strength is very impressive, but we can't necessarily utilize that strength unless it has resistance to fracture."

Ritchie, a senior scientist in the Materials Sciences Division of Berkeley Lab and a leading expert on why materials fail, was co-author of the study along with Ashivni Shekhawat, a Miller Research Fellow in his group. Together they developed a statistical model for the toughness of polycrystalline graphene to better understand and predict failure in the material.

"It's a mathematical model that takes into account the nanostructure of the material," Ritchie said. "We find that the strength varies with the grain size up to a certain extent, but most importantly this is a model that defines graphene's fracture resistance."

Toughness, a material's resistance to fracture, and strength, a material's resistance to deformation, are often mutually incompatible properties. "A structural material has to have toughness," Ritchie explained. "We simply don't use strong materials in critical structures--we try to use tough materials. When you look at such a structure, like a nuclear reactor pressure vessel, it's made of a relatively low-strength steel, not an ultrahigh-strength steel. The hardest steels are used to make tools like a hammer head, but you'd never use them to manufacture a critical structure because of the fear of catastrophic fracture."

As the authors note in their paper, many of the leading-edge applications for which graphene has been suggested--such as flexible electronic displays, corrosion-resistant coatings, and biological devices--implicitly depend on its mechanical properties for structural reliability.

Although pure monocrystalline graphene may have fewer defects, the authors studied polycrystalline graphene as it is more inexpensively and commonly synthesized with chemical vapor deposition. Ritchie is aware of only one experimental measurement of the material's toughness.

"Our numbers were consistent with that one experimental number," he said. "In practical terms these results mean that a soccer ball can be placed on a single sheet of monocrystalline graphene without breaking it. What object can be supported by a corresponding sheet of polycrystalline graphene? It turns out that a soccer ball is much too heavy, and polycrystalline graphene can support only a ping pong ball. Still remarkable for a one-atom thick material, but not quite as breathtaking anymore."

Next, Shekhawat and Ritchie are studying the effects of adding hydrogen to the material. "We don't know a lot about the fracture of graphene, so we're trying to see if it's sensitive to other atoms," he said. "We're finding the cracks grow more readily in the presence of hydrogen."

###

The research was funded by the DOE Office of Science.

Lawrence Berkeley National Laboratory addresses the world's most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab's scientific expertise has been recognized with 13 Nobel prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy's Office of Science. For more, visit http://www.lbl.gov.

DOE's Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

Media Contact

Julie Chao
jhchao@lbl.gov
510-486-6491

 @BerkeleyLab

http://www.lbl.gov 

Julie Chao | EurekAlert!

More articles from Materials Sciences:

nachricht Graphene origami as a mechanically tunable plasmonic structure for infrared detection
25.04.2018 | University of Illinois College of Engineering

nachricht Scientists create innovative new 'green' concrete using graphene
24.04.2018 | University of Exeter

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Why we need erasable MRI scans

New technology could allow an MRI contrast agent to 'blink off,' helping doctors diagnose disease

Magnetic resonance imaging, or MRI, is a widely used medical tool for taking pictures of the insides of our body. One way to make MRI scans easier to read is...

Im Focus: BAM@Hannover Messe: innovative 3D printing method for space flight

At the Hannover Messe 2018, the Bundesanstalt für Materialforschung und-prüfung (BAM) will show how, in the future, astronauts could produce their own tools or spare parts in zero gravity using 3D printing. This will reduce, weight and transport costs for space missions. Visitors can experience the innovative additive manufacturing process live at the fair.

Powder-based additive manufacturing in zero gravity is the name of the project in which a component is produced by applying metallic powder layers and then...

Im Focus: Molecules Brilliantly Illuminated

Physicists at the Laboratory for Attosecond Physics, which is jointly run by Ludwig-Maximilians-Universität and the Max Planck Institute of Quantum Optics, have developed a high-power laser system that generates ultrashort pulses of light covering a large share of the mid-infrared spectrum. The researchers envisage a wide range of applications for the technology – in the early diagnosis of cancer, for instance.

Molecules are the building blocks of life. Like all other organisms, we are made of them. They control our biorhythm, and they can also reflect our state of...

Im Focus: Spider silk key to new bone-fixing composite

University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.

Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.

Im Focus: Writing and deleting magnets with lasers

Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.

Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

IWOLIA: A conference bringing together German Industrie 4.0 and French Industrie du Futur

09.04.2018 | Event News

 
Latest News

World's smallest optical implantable biodevice

26.04.2018 | Power and Electrical Engineering

Molecular evolution: How the building blocks of life may form in space

26.04.2018 | Life Sciences

First Li-Fi-product with technology from Fraunhofer HHI launched in Japan

26.04.2018 | Power and Electrical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>