Nanoscale Thermal Management Research Articles

Thermal conductance modulator based on folded graphene nanoribbons

Based on folded graphene nanoribbons, we report a thermal conductance modulator which performs analogous operations as the rheostat in electronic circuits. This fundamental device can controllably and reversibly modulate the thermal conductance by varying the geometric structures and its tuning range can be up to 40% of the conductance of unfolded nanoribbons (∼1 nm wide and 7–15 nm long). Under this modulation, the conductance shows a linearly dependence on the folded angle, while undergoes a transition with the variation of the inter-layer distance. This primary thermal device may have great potential applications for phononic circuits and nanoscale thermal management.

Nanoengineering Heat Transfer Performance at Carbon Nanotube Interfaces

Carbon nanotubes are superb materials for nanoscale thermal management and phononic devices applications, due to their extremely high thermal conductivity (3000-6600 W/mK) and quasi-one-dimensional geometry. However, the presence of interfaces between individual carbon nanotubes as found widely in nanocomposites, nanoelectronics, and nanodevices severely limits their performance for larger scale applications. Solving this issue requires a deep understanding of the heat transfer mechanism at this nanoscale interface between low-dimensional structures, where conventional models developed for interfaces in bulk materials do not apply. Here we address this challenge through a bottom-up approach based on atomistic simulations. We demonstrate that the huge thermal resistance of carbon nanotube junctions can be significantly improved through modifying the molecular structure at the interface to enhance both the matching of phonon spectra and phonon mode coupling. Specifically, two approaches based on polymer wrapping and metal coatings are investigated here and have shown to improve both the structural stability and interfacial thermal conductivity of carbon nanotube junctions. By properly designing the interface molecular structure between individual carbon nanotubes, significant performance gains up to a factor of 4 can be achieved. These results pave the way for future designs of thermal management networks and phononic devices with thermally transparent and structurally stable interfaces.

Molecular Dynamics Simulation of Interfacial Thermal Resistance Between a (10,10) Carbon Nanotube and SiO2

AbstractUnderstanding thermal transport between carbon nanotubes (CNTs) and dielectric substrates is important both for nanoscale thermal management and CNT device applications. We investi-gate thermal transport between a (10,10) CNT and an SiO2 substrate through non-equilibrium classical molecular dynamics (MD) simulations. The thermal boundary conductance (TBC) is computed by setting up a temperature pulse in the CNT and monitoring its relaxation. The TBC is found to scale nearly linearly with temperature between 200�600 K, where a quantum correction is applied to the CNT heat capacity through its phonon density of states. However, the TBC ap-pears most sensitive to the strength the CNT-substrate interaction, which linearly modulates it between 0.05�0.30 WK-1m-1, in the range suggested by recent experimental data.

Heat transport through plasmonic interactions in closely spaced metallic nanoparticle chains

We report a numerical investigation on the near-field heat transfer through one-dimensional arrays of metallic nanoparticles closely spaced in a host material. Using the Landauer-Buttiker formalism we study the thermal behavior of chains in ballistic regime. It is shown that that the heat transport through plasmonic interactions can be several order of magnitude more efficient than in classical dipolar chains. This result could explain the anomalously high thermal conductivity observed in many nanoparticles based composite media such as nanofluids and could find broad practical applications in nanoscale thermal management.

Thermal resistance of the nanoscale constrictions between carbon nanotubes and solid substrates

We have determined the thermal resistance for transferring heat between individual single-walled carbon nanotube devices and solid substrates. Using sapphire and comparing our results to previous results obtained from SiO2, we find that the resistance is dominated by interfacial resistance rather than the spreading resistance of heat for diffusing into the substrate. Our results are in agreement to a recent model for the thermal resistance of nanoscale constrictions. Our results suggest that relatively short contact lengths (∼10–30nm) to a typical solid should be sufficient to transfer heat efficiently into carbon nanotubes, underscoring the potential of carbon nanotubes for nanoscale thermal management.