Efficient Thermal Rectification in Nitrogen-Doped Carbon Nanotube Heterostructures

Carbon nanotubes (CNTs) are widely used in many fields owing to their unique properties. In this study, three different nitrogen-doped types of CNT heterojunctions were constructed: parallel doped (PCNT), vertically doped (VCNT), and mesh doped (MCNT). Non-equilibrium molecular dynamics (NEMD) simulations were used to investigate their heat flux and thermal rectification (TR) effects. The results show that heat flux preferentially flows from nitrogen-doped regions to undoped regions, exhibiting distinct thermal rectification effects, with PCNT being the most prominent. Interestingly, the TR ratio of the zigzag PCNT is significantly higher than that of the armchair-structured PCNT. Subsequently, we investigated the effects of system length and diameter on the TR ratio of the PCNT, and found that the TR ratio shows a tendency of increasing and then decreasing with the increase of model length. In addition, the effect of defect density on the heat flux of the PCNT is peculiar. Phonon density of states, phonon dispersion, participation ratio and phonon spectral heat flux were employed to analyze the thermal transport behavior of phonons in nanotubes. This study provides insights for developing and designing nitrogen-doped CNT thermal rectifiers.