Enhancement mechanisms of interfacial thermal conductance across graphene-paraffin composites: Molecular dynamics explorations

Phase change composites have attracted significant attention due to their prominent thermal energy storage capacity. However, the interfacial thermal conductance between filler-matrix interface performs a critical impact on the overall thermal conductivity of phase change composites, necessitating deeper mechanistic understanding to advance engineered material design. In this work, thermal transport mechanisms across graphene-paraffin (C22H46) interfaces are systematically determined based on molecular dynamics simulations. The underlying influences of material density, interfacial interaction strength, and vibration spectrum property on interfacial thermal conductance of composite material are investigated using spectral analysis. Results indicate that increasing material density and interfacial binding effect can enhance the thermal transport due to improved van der Waals forces and resonance in the low-frequency region. Specifically, when ρ∗/ε∗ are varied from 0.9/0.5 to 1.3/2.5, the ITC of graphene-paraffin composite can be correspondingly increased from 47.6/35.5 to 96.4/152.4 MW m−2 K−1. Moreover, modulation of vibrational spectrum of graphene causes an unconventional enhancement in interfacial thermal conductance through bridging the phonon transport channels at wide frequency regions. Additionally, the impacts of interfacial thermal conductance, filler fraction, and length on the overall thermal conductivity of graphene-paraffin composites are comprehensively discussed by using effective medium theory. Increasing interfacial thermal transport can provide an efficient approach to modify the thermal performance of a composite, especially with a small filler size. These findings are expected to unveil some intriguing routines for the development of engineered phase change composites.