Two-Dimensional Nanomaterials

Georgia Tech Research News

Ting Zhu an associate professor in the George W. Woodruff School of Mechanical Engineering at Georgia Tech, is shown with a model of the graphene structure. Georgia Tech's calculations and physical experiments at Rice University led to the conclusion that graphene, the one-atom layer of carbon, is only as strong as its weakest link. (Credit: Georgia Institute of Technology)

Graphene is Only as Strong as its Weakest Link: Experiments Determine Real-world Limits of Two-dimensional Carbon

There is no disputing graphene is strong. But new research by Rice University and the Georgia Institute of Technology should prompt manufacturers to look a little deeper as they consider the miracle material for applications.

An electron microscope image shows a pre-crack in a suspended sheet of graphene used to measure the overall strength of the sheet in a test at Rice University. Rice and Georgia Tech scientists performed experiments and theoretical calculations and found that graphene, largely touted for its superior physical strength, is only as strong as its weakest point. (Credit: The Nanomaterials, Nanomechanics and Nanodevices Lab/Rice University)

The atom-thin sheet of carbon is touted not just for its electrical properties but also for its physical strength and flexibility. The bonds between carbon atoms are well known as the strongest in nature, so a perfect sheet of graphene should withstand just about anything. Reinforcing composite materials is among the material’s potential applications.

But materials scientists know perfection is hard to achieve. Researchers Jun Lou at Rice University and Ting Zhu at Georgia Tech have measured the fracture toughness of imperfect graphene for the first time and found it to be somewhat brittle. While it’s still very useful, graphene is really only as strong as its weakest link, which they determined to be “substantially lower” than the intrinsic strength of graphene.

“Graphene has exceptional physical properties, but to use it in real applications, we have to understand the useful strength of large-area graphene, which is controlled by the fracture toughness, ” said Zhu, who is an associate professor in the George W. Woodruff School of Mechanical Engineering at Georgia Tech.

Ting Zhu, right, an associate professor in the George W. Woodruff School of Mechanical Engineering at Georgia Tech, works with graduate students Feifei Fan, seated, and Zhi Zeng to calculate the fracture toughness of graphene that has been pre-cracked. Georgia Tech's calculations and physical experiments at Rice University led to the conclusion that graphene, the one-atom layer of carbon, is only as strong as its weakest link. (Credit: Georgia Institute of Technology)The researchers reported in the journal Nature Communications the results of tests in which they physically pulled graphene apart to see how much force it would take. Specifically, they wanted to see if graphene follows the century-old Griffith theory that quantifies the useful strength of brittle materials.

It does, said Lou, who is an associate professor of materials science and nanoengineering and of chemistry at Rice. “Remarkably, in this case, thermodynamic energy still rules, ” he said.

Ting Zhu an associate professor in the George W. Woodruff School of Mechanical Engineering at Georgia Tech, is shown with a model of the graphene structure. Georgia Tech's calculations and physical experiments at Rice University led to the conclusion that graphene, the one-atom layer of carbon, is only as strong as its weakest link. (Credit: Georgia Institute of Technology)

Imperfections in graphene drastically lessen its strength – with an upper limit of about 100 gigapascals (GPa) for perfect graphene previously measured by nanoindentation – according to physical testing at Rice and molecular dynamics simulations at Georgia Tech. That’s important for engineers to understand as they think about using graphene for flexible electronics, composite material and other applications in which stresses on microscopic flaws could lead to failure.

The Griffith criterion developed by a British engineer during World War I describes the relationship between the size of a crack in a material and the force required to make that crack grow. Ultimately, A.A. Griffith hoped to understand why brittle materials fail.

Graphene, it turns out, is no different from the glass fibers Griffith tested.

“Everybody thinks the carbon-carbon bond is the strongest bond in nature, so the material must be very good, ” Lou said. “But that’s not true anymore, once you have those defects. The larger the sheet, the higher the probability of defects. That’s well known in the ceramic community.”

See also:
Silicon-Based Low-Dimensional Nanomaterials and Nanodevices, 2 Volume Set: Silicon-Based Low-Dimensional Nanodevices and Applications
Book (CRC Press)

Paper battery?

by edsdesk

Mon Dec 7, 4:28 pm ET
WASHINGTON (Reuters) – Ordinary paper could one day be used as a lightweight battery to power the devices that are now enabling the printed word to be eclipsed by e-mail, e-books and online news.
Scientists at Stanford University in California reported on Monday they have successfully turned paper coated with ink made of silver and carbon nanomaterials into a "paper battery" that holds promise for new types of lightweight, high-performance energy storage.
The same feature that helps ink adhere to paper allows it to hold onto the single-walled carbon nanotubes and silver nanowire films

Some ... some not.

by setArcos

Biotechnology, bioinformatics
Emerging technology
Genetic engineering
Synthetic biology, synthetic genomics
Artificial photosynthesis
Anti-aging drugs: resveratrol, SRT1720
Vitrification or cryoprotectant
Hibernation or suspended animation
Stem cell treatments
Personalized medicine
Body implants, prosthesis
In vitro meat
Regenerative medicine
[edit] Energy systems
Emerging technology
Concentrated solar power includes thermal

Graphene: fundamentals and emergent applications  — Chemistry World
In this context, the text offers an extremely timely and valuable perspective on the first of these materials to attain such enormous attention and is an excellent reference by which to direct analogous research towards other two-dimensional nanomaterials.

Silicon-Based Low-Dimensional Nanomaterials and Nanodevices, 2 Volume Set
Book (CRC Press)
Nanoscale Science and Technology Graphene : a new two-dimensional carbon nanomaterials(Chinese Edition)
Book (Science Press)
Pan Stanford Publishing Two-Dimensional Carbon: Fundamental Properties, Synthesis, Characterization, and Applications (Pan Stanford Series on Carbon-Based Nanomaterials)
Book (Pan Stanford Publishing)
CRC Press Two-Dimensional Nanostructures
Book (CRC Press)
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