Molecular-dynamics simulations of thermal transport in carbon nanotubes with structural defects

Abstract

Effects of structural defects on thermal transport in carbon nanotubes are revealed through nonequilibrium molecular-dynamics simulations with the Tersoff-Brenner bond-order potential. The thermal conductivity of carbon nanotubes decreases rapidly down to 25 % with only 1 % vacancy defects. By performing thermal annealing, the vacancy defects are mainly transformed into 5-6 defects consisting of pentagon-hexagon pairs, and the reduced thermal conductivity due to vacancy defects is increased by 4-7 %. This improvement in thermal conductivity can be understood from the result that the thermal resistance of the 5-6 defects is smaller than that of the vacancy defects.

Effects of defects on thermoelectric properties of carbon nanotubes

“…, where Λprist and Λdef are the MFPs in the pristine CNT and induced by defects. Assuming that cph and vg are independent on σ and Λdef is proportional to σ -β , we can obtain the fitting equation, [31], where α and β are fitting parameters. Solid (broken) lines in Fig.…”

“…While the introduction of defects to CNTs, in general, reduces both electrical and thermal conductivity (or conductance), previous works have shown that the electrical and thermal properties have different sensitivity to the type of defect; the extent of reduction varies with the defect types for electrical conductivity [25][26][27][28] but varies less for thermal conductivity [29][30][31]. Note that most of the works so far on the effect of crystal disorder such as defects and strain on the electronic transport properties have been done for metallic CNTs [25][26][27][28]32,33], and there are only a few works on semiconducting CNTs, which dominantly contribute to the thermoelectric performance of CNT sheets.…”

Control of electron- and phonon-derived thermal conductances in carbon nanotubes

“…vacancy defects, isotopes and Stone-Wales defects) reduce the phonon-derived thermal conductivity in CNTs [6,7]. Among these defects, a vacancy defect with three dangling bonds (hereinafter monovacancy) decreases the thermal conductivity most markedly [7]. Monovacancies are generated during the synthesis process or by artificial procedures such as acid purification and ion/electron irradiation.…”

Anomalous satellite inductive peaks in alternating current response of defective carbon nanotubes

“…Although it is known that the atomic vacancy shown in Fig. 1 is not the most stable, [31][32][33][34] this defect is useful for clarifying the effect of defect on physical properties. [13][14][15][16][17][18] We can see two conductance dips: a broad dip around e F ¼ À0.25 eV and a sharp dip around e F ¼ 0.05 eV.…”

“…This defect is composed of two pentagons and two hexagons: hereafter it is called 5-6 defect. 31,32 Figure 2(c) shows the Fermi-level dependence of the DC conductance. It has two dips at e F ¼ À0.7 eV and 0.6 eV due to the electron scattering by the defect states shown in Figs.…”