Hindawi Publishing Corporation Journal of Nanomaterials Volume 2013, Article ID 842819, 7 pages http://dx.doi.org/10.1155/2013/842819 Research Article The Thermal Conductivity of Carbon Nanotubes with Defects and Intramolecular Junctions Qiaoli Zhou, 1 Fanyan Meng, 1 Zhuhong Liu, 1 and Sanqiang Shi 2 1 Department of Physics, School of Mathematics and Physics, University of Science and Technology Beijing, Beijing 100083, China 2 Department of Mechanical Engineering, Hong Kong Polytechnic University, Hong Kong Correspondence should be addressed to Fanyan Meng; meng7707@sas.ustb.edu.cn Received 5 July 2013; Revised 11 November 2013; Accepted 15 November 2013 Academic Editor: Raymond Whitby Copyright © 2013 Qiaoli Zhou et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Te thermal conductivity of various carbon nanotubes with defects or intramolecular junctions was studied using nonequilibrium molecular dynamics approach. Te results show that the thermal conductivity of both armchair and zigzag carbon nanotubes increased with the decrease of the radius of the tube. Te thermal conductivity of armchair tube is higher than that of zigzag tube when the radii of the two tubes are kept almost same. Discontinuities appear on the temperature profle along the tube axial at the region of IMJ, resulting in the large temperature gradient and thus lower thermal conductivity of (, )/(, 0) tube with one IMJ and (, 0)/(, )/(, 0) tube with two IMJs. For the (, 0)/(, )/(, 0) tube with two IMJs, phonon mean free path of the middle (, ) tube is much smaller than that of the isolate (, ) tube. 1. Introduction As the sizes of electronic and mechanical devices are decreased to the micron and nanometre level, there is a great interest in materials that conduct heat efciently, thus pre- venting structural damage [1, 2]. Carbon allotropes and their derivatives occupy a unique place in terms of their ability to conduct heat [3], especially the carbon nanotubes (CNTs). As a typical one-dimensional nanostructure material, CNTs possessing the unique mechanical, thermodynamic, and elec- tronic properties [4–7] have received considerable attention, since the discovery of multiwalled carbon nanotubes by Iijima [8] in 1991 and single-walled nanotubes by Iijima and Ichihashi [9] and Bethune et al. [10] in 1993. Te high thermal conductivities of carbon nanotubes are measured experimen- tally [11–15] and theoretically [1, 2, 16–19], revealing that they are promising building blocks for advanced technologies in the future [20]. Te previous experiments [13, 21–25] have been con- ducted to measure the thermal properties of millimeter-sized CNT mats, graphene and packed carbon nanofbers, which may help us a little further to understand the thermal prop- erties of these materials. Up to now, there are many reports on thermal conductivity of isolated carbon nanotubes and more emphasis on a good medium for the perfect carbon nan- otubes. However, there has been little systematic investigation on the thermal conductivity of nanotubes with defects. Che et al. [1] compared the efects of vacancies with that of Stone- Wales (SW) defects on the thermal conductivity of CNTs. Te calculated results of Cummings et al. [26] demonstrate that a two-atom-vacancy defect is similar to one Y-junction. Te thermal conductivity of CNTs with only 0.25% vacancies decreases 60% at 300 K, which is predicted by Bi et al. [27]. Nevertheless, Kondo et al. [20] reported that the thermal conductivity of carbon nanotubes decreases rapidly down to 25% with only 1% vacancy defects. Meanwhile, Kondo et al. [20] found that the thermal resistance of the 5-6 defects is smaller than that of the vacancy defects. In our previous work, we studied that the thermal conductivity of the nanotube with junctions was 20–80% less than that of a straight nan- otube depending on temperature [28]. Other defects such as isotropic impurities [27],  3 -hybridized defect [29], chemis- orptions [30], and oxidation on the thermal conductivity of SWCNTs were studied. In the following, we investigate the thermal conductivities of various carbon nanotubes with one or two intramolecular junctions (IMJs) using molecular dynamics (MD) approach