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:4/18/2017)... -- Socionext Inc., a global expert in SoC-based imaging and computing solutions, ... which features the company,s hybrid codec technology. A demonstration utilizing TeraFaces ... will be showcased during the upcoming Medtec Japan at Tokyo Big ... Las Vegas Convention Center April 24-27. ... Click here for an image of ...
(Date:4/11/2017)... Apr. 11, 2017 Research and Markets has ... report to their offering. ... The global eye tracking market to grow at a CAGR of ... Eye Tracking Market 2017-2021, has been prepared based on an in-depth ... market landscape and its growth prospects over the coming years. The ...
(Date:4/5/2017)... , April 5, 2017 Today HYPR ... that the server component of the HYPR platform is ... providing the end-to-end security architecture that empowers biometric authentication ... HYPR has already secured over 15 million users across ... manufacturers of connected home product suites and physical access ...
Breaking Biology News(10 mins):
(Date:8/15/2017)... Linda, Ca (PRWEB) , ... August 15, 2017 ... ... coffee production and is threatened by various biotic and abiotic factors. During this ... complex evolutionary history of coffee, as well as gain a better understanding of ...
(Date:8/11/2017)... 2017  Market researcher Kalorama Information was ... regarding the telemedicine market.  The telemedicine market ...  The article, "Heart and Asthma Monitors? ... information from Kalorama Information,s Remote Patient Monitoring ...  (Sleep, Diabetes, Vital Signs /EKG and ...
(Date:8/10/2017)... (PRWEB) , ... August 09, 2017 , ... ... the classroom next week-- as students. From August 14th through the 16th, the ... institute, which debuted in the summer of 2016, provides Philadelphia-based middle school educators ...
(Date:8/10/2017)... ... August 10, 2017 , ... DrugDev and ... webinar to demonstrate how Good Clinical Practice (GCP) can be used throughout ... addition the webinar will discuss the importance of GCP compliance, how sites are affected ...
Breaking Biology Technology: