Thermal Rectification across an Asymmetric Layer Carbon Nanotube van der Waals Heterostructure

Abstract

The exceptional thermal conductivity and strength of carbon nanotubes (CNTs) position them as outstanding materials for thermal conduction. The intriguing properties introduced by van der Waals (vdW) heterojunctions have also captured the interest of researchers. However, further refinement of the research concerning the integration of these two elements is required. In our study, a vdW heterostructure with asymmetric layer nesting of multiwalled CNTs (ALCNTs) is devised, with a specific focus on the model's heat flux and thermal rectification (TR) properties, which are analyzed using nonequilibrium molecular dynamics (NEMD). Notably, the greatest TR ratio is observed in the connection of three-layer and single-layer ALCNTs. Moreover, multilayer variable-length nested models exhibit a sluggish TR ratio. An examination of the interface thermal resistance (ITR) reveals that the maximum ITR in the multilayer nested model resides at the rightmost interface. However, it is essential to highlight that the determinant of the TR ratio and heat flux in the multilayer nested model is not the maximum ITR of the rightmost interface but rather the ITR of the outermost layer on the left. Additionally, the impacts of the defect density, length, temperature difference, and hydrogenation on the model's heat flux and TR are explored, yielding noteworthy conclusions. For instance, defects in the outer CNT have a minimal influence on the heat flux and TR compared with those in the inner CNT. As the length increases, the heat flux initially decreases and then increases. Hydrogenation significantly enhances the model's heat flux but does not favor the TR. Our study contributes to advancing the understanding of CNT vdW heterojunctions and offers valuable insights for their practical applications.

Thermal Rectification in Graphene–Boron Nitride Nanotube Hybrid Structures: An Independent Control Mechanism for Forward and Backward Heat Flux

“…For the forward heat flux, a higher Δ led to increased phonon participation in thermal transport, which is consistent with existing studies. ,,, Additionally, the impact of Δ on the STCs under backward heat fluxes was analyzed as shown in Figure b,c. Figure b shows that in the graphene region, the value of STC considerably increased as Δ rose.…”

“…In this work, we developed graphene–boron nitride nanotube hybrid structures (GR-BNNTs) and observed a TR ratio of approximately 50%. This structure not only achieves significant TR but also maintains larger thermal conductivity in all directions than graphene and CNT rectifiers reported in our previous work. , Additionally, unlike earlier studies on CNTs–graphene hybrids, the present work reveals an independent regulation mechanism for forward and backward heat fluxes in TR formation. Specifically, modulating phonon thermal transport in the interlayer BNNTs can independently alter the forward heat flux without significantly affecting the backward flux.…”

“…However, it was notable that while the forward heat flux continued to increase steadily, the backward heat flux demonstrated minimal growth when Δ rose from 0.2 to 0.3, resulting in the highest TR ratio at this increment. It is different from existing studies, ,,, so the next step is to study this phenomenon in detail.…”

“…found the TR effect in the asymmetric Y-junction CNT bundle. Our previous work studied the TR phenomenon by constructing asymmetric layer nanotube van der Waals heterojunctions , and graphene nanojunctions . In addition, in the PGN system discussed in detail, many studies have also demonstrated the TR phenomenon inside it.…”