Efficient thermal rectification in nitrogen-doped carbon nanotube heterostructures

Abstract Carbon nanotubes (CNTs) are widely used in various fields owing to their unique properties. In this study, three different types of nitrogen-doped CNT heterojunctions were constructed: parallel-doped (PCNT), vertically doped (VCNT), and mesh-doped (MCNT). Non-equilibrium molecular dynamics (NEMD) simulations were conducted 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 behavior, with PCNT showing the most pronounced effect. Interestingly, the TR ratio of the zigzag PCNT is significantly higher than that of the armchair PCNT. Subsequently, we examined the effects of system length and diameter on the TR ratio of the PCNT and found that the TR ratio increases and then decreases with increasing model length. In addition, the effect of defect density on the heat flux of the PCNT is peculiar. The phonon density of states, phonon dispersion, participation ratio, and phonon spectral heat flux were analyzed to elucidate the thermal transport behavior of phonons in the nanotubes. This study provides insights into the development and design of nitrogen-doped CNT thermal rectifiers.