Ballistic Heat Transport in Nanocomposite: the Role of the Shape and Interconnection of Nanoinclusions

TL;DR

This study investigates how the shape and interconnection of nanoinclusions in amorphous silicon influence ballistic heat transport, revealing that interconnected nanostructures can enhance thermal conductivity via phonon ballistic transport.

Contribution

It introduces a detailed analysis of the impact of nanoinclusion interconnection on phonon transport and thermal conductivity in nanocomposites using molecular dynamics simulations.

Findings

Interconnection increases mean free path of high-frequency phonons.

Thermal conductivity is enhanced by crystalline interconnections.

Coherent energy propagation with moderate conductivity increase is possible.

Abstract

The effect on the vibrational and thermal properties of gradually interconnected nanoinclusions embedded in an amorphous silicon matrix is studied using MD simulations. The nanoinclusion arrangement ranges from an aligned sphere array to an interconnected mesh of nanowires. Wave-packet simulations scanning different polarizations and frequencies reveal that the interconnection of the nanoinclusions at constant volume fraction induces a strong increase of the mean free path of high frequency phonons, but does not affect the energy diffusivity. The mean free path and energy diffusivity are then used to estimate the thermal conductivity, showing an enhancement of the effective thermal the effective thermal conductivity due to the existence of crystalline structural interconnections. This enhancement is dominated by the ballistic transport of phonons. Equilibrium molecular dynamics simulations confirm the tendency although less markedly. This leads to the observation that coherent energy propagation with a moderate increase of the thermal conductivity is possible.