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.
Courtney Anderson | EurekAlert!
Researchers shoot for success with simulations of laser pulse-material interactions
29.03.2017 | DOE/Oak Ridge National Laboratory
Nanomaterial makes laser light more applicable
28.03.2017 | Christian-Albrechts-Universität zu Kiel
The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.
To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
30.03.2017 | Physics and Astronomy
30.03.2017 | Studies and Analyses
30.03.2017 | Life Sciences