Thermal Transport Properties of Nanoporous Silicon with Significant Specific Surface Area

TL;DR

This study investigates how nanoporous silicon's thermal conductivity depends on specific surface area and porosity, developing models that align well with molecular dynamics data across various porosity levels.

Contribution

The paper introduces a modified phonon transport kinetic theory model that accurately predicts thermal conductivity in nanoporous silicon across different porosities.

Findings

Model 2 accurately predicts thermal conductivity for all porosities.

Thermal conductivity decreases with increasing surface area and porosity.

Phonon mean free path dependence is crucial for thermal transport modeling.

Abstract

This paper studies thermal transport in nanoporous silicon with a significant specific surface area. First, the equilibrium molecular dynamics approach was used to obtain the dependence of thermal conductivity on a specific surface area. Then, a modified phonon transport kinetic theory-based approach was developed to analyze thermal conductivity. Two models were used to evaluate the phonon mean free path in the porous materials. The first model approximates the dependence of the mean free path only with the specific surface area, and the second one investigates the dependence of the mean free path variation with the porosity in the peculiar case of a highly porous matrix. Both models approximate molecular dynamics data well for the smaller porosity values, while the first model fails for large porosities. The second model matches well with molecular dynamics simulations for all considered ranges of the porosities. This work illustrates that the phonon mean free path dependence with the porosity/volume fraction of composite materials is essential for describing thermal transport in systems with significant surface-to-volume fractions.