Nanotechnology Now

Our NanoNews Digest Sponsors

Heifer International

Wikipedia Affiliate Button

Home > Press > Boron nanoribbons reveal surprising thermal properties in bundles

Abstract:
Boron Nanoribbons Reveal Surprising Thermal Properties in Bundles Size matters… but apparently so does shape - when it comes to conducting heat in very small spaces.

Boron nanoribbons reveal surprising thermal properties in bundles

Charlotte, NC | Posted on December 20th, 2011

Researchers looking at the thermal conductivity of boron nanoribbons have found that they have unusual heat-transfer properties when compared to other wire/tube-like nanomaterials. While past experiments have shown that bundles of non-metallic nanostructures are less effective in conducting heat energy than single nanostructures, a new study shows that bundling boron nanoribbons can have the opposite effect and "the thermal conductivity of a bundle of boron nanoribbons can be significantly higher than that of a single free-standing nanoribbon," according to a report in Nature Nanotechnology, published online on December 11.

The finding is the result of work by a multidisciplinary team headed by Ravi Prasher of the Advanced Research Projects Agency, Terry Xu of the University of North Carolina at Charlotte, and Deyu Li of Vanderbilt University (see a complete list of authors below).

Additionally, the researchers found that the unusual heat-transfer properties of boron nanoribbon bundles can be modified, allowing the higher thermal conductivity to be switched on and off through relatively simple physical manipulation. The study concludes that the ribbon structure of the nanomaterials is strongly related to the unusual thermal conductivity of the bundles.

Boron-based nanostructures are a promising class of high temperature thermoelectric materials -- substances that can convert waste heat to useful electricity - and thermal conductivity is related to other thermoelectric properties. Physicists describe the transmission of heat energy in materials like boron as happening through the conduction of "phonons," quasi-wave-particles that carry energy through excitations of the material's atoms.

"What we found was largely unexpected," said Xu. "When two nanoribbons were put together, the thermal conductivity was found to rise significantly rather than staying the same or going down, as has been the case in previous measurements. It has been assumed that phonons were hampered by the interface between the individual nanostructures in similar materials.

"That seems to mean that the phonon can pass effectively through the interface between two boron nanoribbons," she said. "The question is whether or not this result is due to the weak van der Waals interactions between two nanostructures of ultra-flat geometry."

The team suspects that the reason for the enhanced thermal conductivity is due in large part to the flat surface structure of the nanoribbons, based on another experimental result that the group discovered by accident.

The nanoribbon bundles exhibiting the unexpectedly higher thermal conductivity were originally prepared in a solution of reagent alcohol and water, which was then allowed to evaporate, leaving some nanoribbons drawn together by van der Waals force (the weak attraction that non reactive and uncharged substances can have for each other). When other members of the team attempted to duplicate this result, however, the experiment failed and the bundles only had the lower thermal conductivity of single ribbons. The researchers then noted that a significant difference between the two attempts was that the second experiment had used isopropyl alcohol rather than reagent alcohol in the solution. Since isopropyl alcohol was known to leave minute residue following evaporation, the researchers suspected that a residue was forming on the ribbons surfaces - a fact that microscopy confirmed -- and the residue apparently prevented tight contact between two nanoribbons. Further tests were made on the lower-conducting bundles, where the ribbon interfaces were washed with reagent alcohol to remove the isopropyl residue, and in this experiment the higher thermal conductivity was achieved.

The results point to the conclusion that boron nanoribbons form better heat-conducting bundles because the ribbons flat surfaces allow for tighter, more complete contact between the individual structures through van der Waals interaction and improved transmission of phonons overall.

"The result implies that achieving a tight van der Waals interface between the ribbons is important in thermal conductivity, something their geometry encourages," Xu said. "It is possible that this result may have implications for other materials with ribbon-based nanostructures."

Xu notes that there are potential engineering applications for the finding come not just from the improved thermal conductivity of boron nanoribbon bundles, but also from the reversible nature of the effect.

"This may lead to a simple way to switch the thermal conductivity of the bundle on and off," she said. "If you want more heat dissipated, but only in certain conditions, you can apply a solution to create a bundle structure with tight bonds and higher thermal conductivity. It could similarly be reversed by adding a residue between the nanoribbons and reducing the thermal conductivity to that of an individual ribbon."

The finding appears in a letter to Nature Nanotechnology. The authors are Juekuan Yang, Yang Yang, Scott Waltermire and Deyu Li from Vanderbilt University; Xiaoxia Wu, Haitao Zhang, Timothy Gutu, Youfei Jiang, and Terry Xu from UNC Charlotte; Yunfei Chen from Southwest University in Nanjing, China; Alfred Zinn from Lockheed Martin Space Systems and Ravi Prasher from the Advanced Research Projects Agency in the US Department of Energy. This research was funded by the National Science Foundation and Lockheed Martin.

####

For more information, please click here

Contacts:
James Hathaway

704-687-5743

Copyright © University of North Carolina at Charlotte

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 News Press

News and information

DNA triggers shape-shifting in hydrogels, opening a new way to make 'soft robots' September 21st, 2017

Physicists develop new recipes for design of fast single-photon gun Physicists develop high-speed single-photon sources for quantum computers of the future September 21st, 2017

GLOBALFOUNDRIES Announces Availability of mmWave and RF/Analog on Leading FDX™ FD-SOI Technology Platform: Technology solution delivers ‘connected intelligence’ to next generation high-volume wireless and IoT applications with lower power and significantly reduced cost September 20th, 2017

GLOBALFOUNDRIES Announces Availability of Embedded MRAM on Leading 22FDX® FD-SOI Platform: Advanced embedded non-volatile memory solution delivers ‘connected intelligence’ by expanding SoC capabilities on the 22nm process node September 20th, 2017

Govt.-Legislation/Regulation/Funding/Policy

DNA triggers shape-shifting in hydrogels, opening a new way to make 'soft robots' September 21st, 2017

Copper catalyst yields high efficiency CO2-to-fuels conversion: Berkeley Lab scientists discover critical role of nanoparticle transformation September 20th, 2017

Solar-to-fuel system recycles CO2 to make ethanol and ethylene: Berkeley Lab advance is first demonstration of efficient, light-powered production of fuel via artificial photosynthesis September 19th, 2017

New insights into nanocrystal growth in liquid: Understanding process that creates complex crystals important for energy applications September 14th, 2017

Discoveries

DNA triggers shape-shifting in hydrogels, opening a new way to make 'soft robots' September 21st, 2017

Physicists develop new recipes for design of fast single-photon gun Physicists develop high-speed single-photon sources for quantum computers of the future September 21st, 2017

Copper catalyst yields high efficiency CO2-to-fuels conversion: Berkeley Lab scientists discover critical role of nanoparticle transformation September 20th, 2017

Solar-to-fuel system recycles CO2 to make ethanol and ethylene: Berkeley Lab advance is first demonstration of efficient, light-powered production of fuel via artificial photosynthesis September 19th, 2017

Materials/Metamaterials

Copper catalyst yields high efficiency CO2-to-fuels conversion: Berkeley Lab scientists discover critical role of nanoparticle transformation September 20th, 2017

New quantum phenomena in graphene superlattices September 18th, 2017

New insights into nanocrystal growth in liquid: Understanding process that creates complex crystals important for energy applications September 14th, 2017

Corrosion in real time: UCSB researchers get a nanoscale glimpse of crevice and pitting corrosion as it happens September 14th, 2017

Announcements

DNA triggers shape-shifting in hydrogels, opening a new way to make 'soft robots' September 21st, 2017

Physicists develop new recipes for design of fast single-photon gun Physicists develop high-speed single-photon sources for quantum computers of the future September 21st, 2017

GLOBALFOUNDRIES Introduces New 12nm FinFET Technology for High-Performance Applications September 20th, 2017

Copper catalyst yields high efficiency CO2-to-fuels conversion: Berkeley Lab scientists discover critical role of nanoparticle transformation September 20th, 2017

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