Nanotechnology Now

Our NanoNews Digest Sponsors





Heifer International

Wikipedia Affiliate Button


DHgate

Home > Press > In nanotube growth, errors are not an option: Rice, Hong Kong Polytechnic, Tsinghua researchers probe healing of nanotube defects

Defects in nanotubes heal very quickly in a very small zone at or near the iron catalyst before they ever get into the tube wall, according to calculations by theoretical physicists at Rice University, Hong Kong Polytechnic University and Tsinghua
Defects in nanotubes heal very quickly in a very small zone at or near the iron catalyst before they ever get into the tube wall, according to calculations by theoretical physicists at Rice University, Hong Kong Polytechnic University and Tsinghua

Abstract:
At the right temperature, with the right catalyst, there's no reason a perfect single-walled carbon nanotube 50,000 times thinner than a human hair can't be grown a meter long.

In nanotube growth, errors are not an option: Rice, Hong Kong Polytechnic, Tsinghua researchers probe healing of nanotube defects

Houston, TX | Posted on June 18th, 2012

That calculation is one result of a study by collaborators at Rice, Hong Kong Polytechnic and Tsinghua universities who explored the self-healing mechanism that could make such extraordinary growth possible. That's important to scientists who see high-quality carbon nanotubes as critical to advanced materials and, if they can be woven into long cables, power distribution over the grid of the future.

The report published online by Physical Review Letters is by Rice theoretical physicist Boris Yakobson; Feng Ding, an adjunct assistant professor at Rice and an assistant professor at Hong Kong Polytechnic; lead author Qinghong Yuan, a postdoctoral researcher at Hong Kong Polytechnic; and Zhiping Xu, a professor of engineering mechanics at Tsinghua and a former postdoctoral researcher at Rice.

They determined that iron is the best and quickest among common catalysts at healing topological defects - rings with too many or too few atoms - that inevitably bubble up during the formation of nanotubes and affect their valuable electronic and physical properties. The right combination of factors, primarily temperature, leads to kinetic healing in which carbon atoms gone astray are redirected to form the energetically favorable hexagons that make up nanotubes and their flat cousin, graphene. The team employed density functional theory to analyze the energies necessary for the transformation.

"It is surprising that the healing of all potential defects — pentagons, heptagons and their pairs — during carbon nanotube growth is quite easy," said Ding, who was a research scientist in Yakobson's Rice lab from 2005 to 2009. "Only less than one-10 billionth may survive an optimum condition of growth. The rate of defect healing is amazing. If we take hexagons as good guys and others as bad guys, there would be only one bad guy on Earth."

The energies associated with each carbon atom determine how it finds its place in the chicken-wire-like form of a nanotube, said Yakobson, Rice's Karl F. Hasselmann Chair in Engineering and a professor of materials science and mechanical engineering and of chemistry. But there has been a long debate among scientists over what actually happens at the interface between the catalyst and a growing tube.

"There have been two hypotheses," Yakobson said. "A popular one was that defects are being created quite frequently and get into the wall of the tube, but then later they anneal. There's some kind of fixing process. Another hypothesis is that they basically don't form at all, which sounds quite unreasonable.

"This was all just talk; there was no quantitative analysis. And that's where this work makes an important contribution. It evaluates quantitatively, based on state-of-the-art computations, specifically how fast this annealing can take place, depending on location," he said.

A nanotube grows in a furnace as carbon atoms are added, one by one, at the catalyst. It's like building the peak of a skyscraper first and adding bricks to the bottom. But because those bricks are being added at a furious rate - millions in a matter of minutes - mistakes can happen, altering the structure.

In theory, if one ring has five or seven atoms instead of six, it would skew the way all subsequent atoms in the chain orient themselves; an isolated pentagon would turn the nanotube into a cone, and a heptagon would turn it into a horn, Yakobson said.

But calculations also showed such isolated defects cannot exist in a nanotube wall; they would always appear in 5/7 pairs. That makes a quick fix easier: If one atom can be prompted to move from the heptagon to the pentagon, both rings come up sixes.

The researchers found that very transition happens best when carbon nanotubes are grown at temperatures around 930 kelvins (1,214 degrees Fahrenheit). That is the optimum for healing with an iron catalyst, which the researchers found has the lowest energy barrier and reaction energy among the three common catalysts considered, including nickel and cobalt.

Once a 5/7 forms at the interface between the catalyst and the growing nanotube, healing must happen very quickly. The further new atoms push the defect into the nanotube wall, the less likely it is to be healed, they determined; more than four atoms away from the catalyst, the defect is locked in.

Tight control of the conditions under which nanotubes grow can help them self-correct on the fly. Errors in atom placement are caught and fixed in a fraction of a millisecond, before they become part of the nanotube wall.

The researchers also determined through simulations that the slower the growth, the longer a perfect nanotube could be. A nanotube growing about 1 micrometer a second at 700 kelvins could potentially reach the meter milestone, they found.

The work at Rice University was initially supported by the National Science Foundation and at a later stage by an Office of Naval Research grant.

####

About Rice University
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 known for its “unconventional wisdom.” With 3,708 undergraduates and 2,374 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 has been ranked No. 1 for best quality of life multiple times by the Princeton Review and No. 4 for “best value” among private universities by Kiplinger’s Personal Finance. To read “What they’re saying about Rice,” go to www.rice.edu/nationalmedia/Rice.pdf.

For more information, please click here

Contacts:
David Ruth
713-348-6327


Mike Williams
713-348-6728

Copyright © Rice University

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related Links

Read the abstract at:

Related News Press

News and information

Oxford Instruments’ Triton Cryofree dilution refrigerator selected by Oxford University for developing scalable quantum nanodevices September 2nd, 2015

JEOL Introduces New Best-in-Class Field Emission SEM September 2nd, 2015

TCL and QD Vision Demonstrate the Future of Wide Color Gamut Television at IFA: Color IQ Based Display is the First Commercially-Branded Television to Present Over 90% of ITU Rec. 2020 Color Gamut September 2nd, 2015

Atomic Force Microscopes from Asylum Research Guide the Development of Thin Film Deposition and Etch Processes September 2nd, 2015

Chemistry

A new technique to make drugs more soluble August 28th, 2015

Nanocatalysts improve processes for the petrochemical industry August 28th, 2015

Researchers combine disciplines, computational programs to determine atomic structure August 26th, 2015

Laser-burned graphene gains metallic powers: Rice University scientists find possible replacement for platinum as catalyst August 20th, 2015

Govt.-Legislation/Regulation/Funding/Policy

For 2-D boron, it's all about that base: Rice University theorists show flat boron form would depend on metal substrates September 2nd, 2015

Silk bio-ink could help advance tissue engineering with 3-D printers September 2nd, 2015

A marine creature's magic trick explained: Crystal structures on the sea sapphire's back appear differently depending on the angle of reflection September 2nd, 2015

Sustainable nanotechnology center September 1st, 2015

Nanotubes/Buckyballs/Fullerenes

For 2-D boron, it's all about that base: Rice University theorists show flat boron form would depend on metal substrates September 2nd, 2015

$200K Awarded to Develop In Vitro Lung Test for Toxicity of Inhaled Nanomaterials: In Vitro Lung Test Designed to Protect Human Health and Replace Animal Testing September 1st, 2015

Developing Component Scale Composites Using Nanocarbons August 26th, 2015

Southampton scientists find new way to detect ortho-para conversion in water August 25th, 2015

Discoveries

For 2-D boron, it's all about that base: Rice University theorists show flat boron form would depend on metal substrates September 2nd, 2015

Silk bio-ink could help advance tissue engineering with 3-D printers September 2nd, 2015

Phagraphene, a 'relative' of graphene, discovered September 2nd, 2015

A marine creature's magic trick explained: Crystal structures on the sea sapphire's back appear differently depending on the angle of reflection September 2nd, 2015

Materials/Metamaterials

Sustainable nanotechnology center September 1st, 2015

Using ultrathin sheets to discover new class of wrapped shapes: UMass Amherst materials researchers describe a new regime of wrapped shapes August 31st, 2015

An engineered surface unsticks sticky water droplets August 31st, 2015

New material science research may advance tech tools August 31st, 2015

Announcements

For 2-D boron, it's all about that base: Rice University theorists show flat boron form would depend on metal substrates September 2nd, 2015

Silk bio-ink could help advance tissue engineering with 3-D printers September 2nd, 2015

Phagraphene, a 'relative' of graphene, discovered September 2nd, 2015

A marine creature's magic trick explained: Crystal structures on the sea sapphire's back appear differently depending on the angle of reflection September 2nd, 2015

Military

Seeing quantum motion August 30th, 2015

These microscopic fish are 3-D-printed to do more than swim: Researchers demonstrate a novel method to build microscopic robots with complex shapes and functionalities August 26th, 2015

Nanotechnology that will impact the Security & Defense sectors to be discussed at NanoSD2015 conference August 25th, 2015

Industrial Nanotech, Inc. Provides Update On Hospital Project, PCAOB Audit, and New Heat Shield™ Line August 24th, 2015

Research partnerships

Turning clothing into information displays September 2nd, 2015

Sustainable nanotechnology center September 1st, 2015

$200K Awarded to Develop In Vitro Lung Test for Toxicity of Inhaled Nanomaterials: In Vitro Lung Test Designed to Protect Human Health and Replace Animal Testing September 1st, 2015

Hot electrons point the way to perfect light absorption: Physicists study how to achieve perfect absorption of light with the help of rough ultrathin films September 1st, 2015

NanoNews-Digest
The latest news from around the world, FREE



  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project







Car Brands
Buy website traffic