Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Nanotube letters spell progress

08.12.2015

Rice team characterizes, analyzes stiffness of individual branching nanotubes

Never mind the ABCs. Rice University scientists interested in nanotubes are studying their XYΩs.


Rice University scientists used a picoindenter to measure the stiffness of junctions in a nanotube "alphabet." They determined its letters handle strain to varying degrees depending on their form.

Credit: Evgeni Penev/Rice University

Carbon nanotubes grown in a furnace aren't always straight. Sometimes they curve and kink, and sometimes they branch off in several directions. The Rice researchers realized they now had the tools available to examine just how tough those branches are.

They used experiments and simulations to study the stiffness of joined nanotubes and found significant differences that are defined by their forms. It turned out that some types are tougher than others, and that all may have their uses if and when nanotubes are used to build macroscale structures.

The team led by Rice materials scientist Pulickel Ajayan and theoretical physicist Boris Yakobson named their nanotubes for their shapes: I for straight nanotubes, Y for branched, X for covalently joined tubes that cross, the lambda symbol (an upside-down "V") for nanotubes that join at any angle and the omega symbol (Ω) for noncovalent tubes that bind through van der Waals and other forces.

They said targeted synthesis of this "nanotube alphabet" may provide material for future nanoscale structures with tunable mechanisms.

The study was published by the American Chemical Society's Nano Letters.

"We needed some sort of language to describe the specific configuration of the junctions, so we thought, 'Let's use letters,'" said Evgeni Penev, a co-author and research scientist in Yakobson's group.

Chandra Sekhar Tiwary, a postdoctoral researcher in the Ajayan lab, prodded the nanotube junctions with a PicoIndenter that measures force and displacement in nanonewtons (billionths of a newton, a unit of force) and nanometers. The PicoIndenter was installed on a scanning electron microscope at Hysitron, a nanomechanical test-instrument manufacturing and testing company in Minneapolis.

Nanotubes grown by Rice graduate student Sehmus Ozden were dispersed in a solution, dried on silicon and placed under the microscope, where Tiwary scanned them for candidate "letters." He then had to be sure those candidates were single units and not just two separate nanotubes. "The space between the tubes could be as little as 1 nanometer but the resolution of the microscope was 5 nanometers, so we had to pick up one side (of the nanotubes) to be sure they were truly welded," he said. "If the nanotubes separated easily, we moved on to the next candidate."

Applying the probe to a particular spot on an individual nanotube was a test of patience, Tiwary said. Once a good candidate appeared, he and Hysitron senior staff scientist and co-author Sanjit Bhowmick zeroed in on the junction and, over 20 minutes, slowly applied and released enough pressure to compress it without breaking it. "In the old days, these tests used brute force, but the new tools are remarkable," Tiwary said. "We were able to watch as we compressed the nanotubes."

Among the atomically bonded tubes, they found the X's were the stiffest and most able to bounce back to nearly their original shapes. Next came Y's and then the any-angle lambdas, but all were left with dents because of newly created links between the inner walls. The I's and omegas, with no covalent bonds joining them to other nanotubes, returned to their original configurations.

The experimentalists turned to graduate student Yang Yang of Yakobson's theoretical group to help understand the mechanism by which the nanotubes handled stress. Yang created atom-level, triple-walled computer models of each "letter" and tested their strength with virtual probes.

"In experiments, we get what is happening quantitatively, but they cannot tell us what is happening inside the tubes," Tiwary said. "Until they did the calculations, we didn't really know how carbon nanotube junctions behaved."

The answer had to do with the atomic geometry at the junctions. Where nanotubes join, carbon atoms that normally come together in six-member rings are often forced to change their configurations, adjusting to five- and seven-member rings (known as dislocations) to remain in the lowest-energy state.

The number of dislocations required to make a nanotube branch is different for each angle. Because the dislocations take the brunt of the force, those variations determine the overall stiffness of the nanotube letter, they determined.

Previous research by Yakobson's group found that while graphene, the atom-thick, chicken-wire-like form of carbon, is extraordinarily strong, it does not stretch very well. But the new simulations also showed the local walls of the nanotubes (which are basically rolled-up graphene) stretch enough to distribute strain applied to the junctions.

Penev suggested that nanotube carpets of certain letters could have material benefits. "Imagine if all the nanotubes were upside-down 'Y' shapes," he said. "Such a carpet would be much harder to crush under pressure."

One question now is whether scientists can grow homogenous batches of letters. "Can we have all Y's and align them perfectly? Or can we have all X interconnects and then make a structure?" Tiwary asked. "That is going to be the next challenge, but it's just a matter of people putting time into it. I'm optimistic."

###

Syed Asif, director of research and development at Hysitron, is a co-author of the paper. Yakobson is the Karl F. Hasselmann Professor of Materials Science and NanoEngineering and a professor of chemistry. Ajayan is chair of Rice's Department of Materials Science and NanoEngineering, the Benjamin M. and Mary Greenwood Anderson Professor in Engineering and a professor of chemistry.

The research was supported by the U.S. Department of Defense Air Force Office of Scientific Research for the Project MURI: "Synthesis and Characterization of 3-D Carbon Nanotube Solid Networks." Computer resources were provided by XSEDE and Rice's DAVinCI cluster, both supported by the National Science Foundation.

Read the abstract at http://pubs.acs.org/doi/abs/10.1021/acs.nanolett.5b03607

This news release can be found online at http://news.rice.edu/2015/12/07/nanotube-letters-spell-progress-2/

Follow Rice News and Media Relations via Twitter @RiceUNews

Video:

https://youtu.be/WO6IQ6K_H-w

Related Materials:

Ajayan Research Group: http://ajayan.rice.edu

Yakobson Research Group: http://biygroup.blogs.rice.edu

Rice Department of Materials Science and NanoEngineering: https://msne.rice.edu

George R. Brown School of Engineering: http://engr.rice.edu

Images for download:

http://news.rice.edu/wp-content/uploads/2015/12/1207_ALPHABET-1-web.jpg

Rice University researchers tested the stiffness of individual nanotube junctions with a combined scanning electron microscope and picoindenter. It allowed them to analyze nanotubes in real time. (Credit: Evgeni Penev/Rice University)

http://news.rice.edu/wp-content/uploads/2015/12/1102_ALPHABET-2-web.jpg

Rice University scientists used a picoindenter to measure the stiffness of junctions in a nanotube "alphabet." They determined its letters handle strain to varying degrees depending on their form. (Credit: Illustration by Evgeni Penev/Rice University)

http://news.rice.edu/wp-content/uploads/2015/12/1102_ALPHABET-3-web.jpg

A picoindenter approaches the junction of a branched nanotube in an experiment carried out by Rice University scientists. The researchers discovered these nanotube "letters" handle strain to varying degrees depending on their form. (Credit: Hysitron)

Located on a 300-acre forested campus in Houston, Rice University is consistently ranked among the nation's top 20 universities by U.S. News & World Report. Rice has highly respected schools of Architecture, Business, Continuing Studies, Engineering, Humanities, Music, Natural Sciences and Social Sciences and is home to the Baker Institute for Public Policy. With 3,910 undergraduates and 2,809 graduate students, Rice's undergraduate student-to-faculty ratio is 6-to-1. Its residential college system builds close-knit communities and lifelong friendships, just one reason why Rice is ranked No. 1 for best quality of life and for lots of race/class interaction by the Princeton Review. Rice is also rated as a best value among private universities by Kiplinger's Personal Finance. To read "What they're saying about Rice," go to http://tinyurl.com/AboutRiceUniversity.

David Ruth
713-348-6327
david@rice.edu

Mike Williams
713-348-6728
mikewilliams@rice.edu

http://news.rice.edu 

David Ruth | EurekAlert!

More articles from Materials Sciences:

nachricht Researchers printed graphene-like materials with inkjet
18.08.2017 | Aalto University

nachricht Superconductivity research reveals potential new state of matter
17.08.2017 | DOE/Los Alamos National Laboratory

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

A Map of the Cell’s Power Station

18.08.2017 | Life Sciences

Engineering team images tiny quasicrystals as they form

18.08.2017 | Physics and Astronomy

Researchers printed graphene-like materials with inkjet

18.08.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>