Tunable anisotropic thermal transport in porous carbon foams: The role of phonon coupling

Carbon foams (CFs) possess high storage capacity, good electronic conductivity and superb mechanical strength, which demonstrate promising applications in many engineering fields. Understanding thermal transport in CFs is critical for the design and reliability of functional electronic devices based on them. In this work, we systematically study anisotropic thermal transport in the CFs composed of sixfold-wing graphene nanoribbons by using equilibrium molecular dynamics simulations. The results showed that the remarkable anisotropic behavior reflecting geometric anisotropy can be attributed to the orientation-dependent group velocity of long wavelength phonons. Moreover, it is found that the anisotropic ratio could be effectively regulated by compress/tensile strains. Detailed spectral analysis revealed that the loading of strain would significantly modify the coupling level between the transverse and longitudinal vibrational modes, resulting in a change to the anisotropic ratio. For thermal management application, the interfacial thermal conductance (TBC) of CFs/silicon substrate is predicted to be about 35 MW/m(2) K-1, which is comparable to the TBC of the transferred metal films on silicon or SiO2 substrates. Furthermore, the TBC could be further enhanced by increasing ambient temperature or external stress. Our results might provide guidance for the development of thermal interfacial materials and thermal channeling devices.