Effects of length, diameter, and doping on the thermal transport in carbon nanotubes: a molecular dynamics study

In this study, we have investigated numerous influential factors such as length, diameter, impurity introduction, and vacancy defects on the thermal conductivity of carbon nanotubes (CNTs). These investigations were conducted through molecular dynamics simulations using the large-scale atomic/molecular massively parallel simulator (LAMMPS). It is observed that longer CNTs tend to exhibit heightened thermal conductivity, a consequence of the increased support for phonon vibration modes that facilitate efficient thermal transport. Furthermore, CNTs with larger diameters display superior thermal characteristics owing to reduced phonon scattering effects. The introduction of boron doping reduces CNTs thermal conductivity by approximately 3% with the inclusion of 6% boron atoms, whereas nitrogen doping increases it by a similar margin. These doping effects hold great potential for optimizing the performance of MEMS and NEMS devices. This duality in doping offers a versatile means to fine-tune the thermal conductivity of CNTs, enabling effective heat management in micro/nanodevices. By strategically modulating thermal conductivity, we can optimize the heat transfer properties of CNT-based materials and devices. This optimization is of utmost importance in ensuring efficient heat dissipation and averting thermal-induced issues, such as overheating, performance degradation, or failure. Additionally, this paper explores how vacancy defects impact the thermal conductivity of CNTs. By varying the vacancy concentration from 1 to 6%, a decrease in thermal conductivity of approximately 2% to 4% was observed in both SWCNTs and DWCNTs. These results emphasize the pivotal role of defects in perturbing the efficient phonon transport mechanisms in CNTs and suggest the potential for customizing CNTs with specific defect concentrations to enhance their suitability for thermoelectric devices and thermal insulation materials.