Navigation Links
Boron nanoribbons reveal surprising thermal properties in bundles
Date:12/20/2011

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.

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."
'/>"/>

Contact: James Hathaway
jbhathaw@uncc.edu
704-687-5743
University of North Carolina at Charlotte
Source:Eurekalert

Related biology news :

1. European researchers harness unique properties of boron to develop new drugs and diagnostics
2. Boron-based compounds trick a biomedical protein
3. Armchair nanoribbons made into spintronic device
4. £2 million study to reveal workings of dementia genes
5. Study reveals homeowner perceptions in fire-prone areas
6. Study reveals specific gene in adolescent men with delinquent peers
7. 6 environmental research studies reveal critical health risks from plastic
8. Revealing the evolutionary history of threatened sea turtles
9. Details of evolutionary transition from fish to land animals revealed
10. UGA study reveals ecosystem-level consequences of frog extinctions
11. Tick-borne encephalitis virus reveals its access code
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:3/16/2017)... CeBIT 2017 - Against identity fraud with DERMALOG solutions "Made in ... ... Used combined in one project, multi-biometric solutions provide a crucial contribution against identity fraud. ... Used combined in one project, multi-biometric solutions ... ...
(Date:3/9/2017)... , March 9, 2017 4Dx has ... World Lung Imaging Workshop at the University of Pennsylvania. ... invited to deliver the latest data to world leaders ... event brings together leaders at the forefront of the ... lung imaging. "The quality of the ...
(Date:3/7/2017)... -- Brandwatch , the leading social intelligence company, today announces ... to uncover insights to support its reporting, help direct future campaigns, ... leading youth charity will be using Brandwatch Analytics social listening and ... understanding of the topics and issues that are a priority for ... "Until ...
Breaking Biology News(10 mins):
(Date:4/21/2017)... ... April 21, 2017 , ... Frederick Innovative Technology Center, ... emerging technology-based businesses, recently earned a $77,518 grant from the Rural Maryland Council ... 2004, FITCI is Frederick’s first incubator. A non-profit corporation, FITCI is a public-private ...
(Date:4/20/2017)... ... April 20, 2017 , ... ... their strategic partnership to offer a full spectrum of digital security goods and ... of biometric products and the ground-breaking proactive cybersecurity services and products through Assured ...
(Date:4/20/2017)... ... 2017 , ... USDM Life Sciences , the leading risk management, technological ... pleased to announce Holger Braemer as Vice President of its Europe division ... Germany. , Braemer is an integral part of USDM’s expansion of services and ...
(Date:4/20/2017)... ... April 20, 2017 , ... NetDimensions appoints Bill Mastin, a ... over 20 years of experience in the learning technologies industry, Mastin joins NetDimensions from ... Learning Technologies Group plc (LTG). At LEO, Mastin served as SVP of the North ...
Breaking Biology Technology: