Thermal Conductivity Enhancement by Optical Phonon Sub-Band Engineering of Nanostructures Based on C and BN
TEXAS UNIV AT DALLAS RICHARDSON NANOTECH INST
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It is expected that a single-wall carbon nanotube SWCN is a very promising object for creation of metamaterials with a high thermal conductivity TC 1,2. The first reason for this expectation is that carbon-based materials, like diamond, have the largest known TC and, the second reason is a molecular perfection of the SWCNs 1. However, to the best of my knowledge, the highest TC ever observed in SWCN bundles at room temperature is about 220 WmK and it is ten times smaller than the TC of the natural diamond 3. This highest result has been reported by Hone et al. 4 for a bulk sample of magnetically aligned nanotubes. The aligned SWCNs form a bundle in which all tubes have a preferable orientation in some direction. Hone et al. showed that the TC of the aligned SWCNs is strongly anisotropic with the largest value in the direction of the alignment. The enhancement of the TC due to the alignment has been observed also by Zhou et al. 5 and by Choi et al. 6, but the absolute values of the reported TC have been significantly smaller than in 4. There are many theoretical works on TC of the SWCNs. Some computational ones 7- 10 are made by molecular dynamics simulations. The results of these simulations have different values and different T-dependences. They predict mostly very high values of the room temperature TC for example 6000 in 7. Evidently, the main problem of all these works is the small size of the array that can be simulated. There are also some different analytical approaches to the problem 11,12 and wonderful reviews 13-15. The purpose of this research is to estimate the maximum TC value of aligned nanotubes taking into account that they do necessarily consist of segments with a finite length. It is well known, that tubes in ropes are not infinitely long, but have brakes, because each method of synthesis is able to create separated tubes of only a certain length.
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