# Elimination of Extreme Boundary Scattering via Polymer Thermal Bridging in Silica Nanoparticle Packings: Implications for Thermal Management

## TL;DR

This study demonstrates that polymer filling in silica nanoparticle packings eliminates boundary scattering and unexpectedly enhances thermal conductivity, offering new insights into thermal management in disordered nanostructures.

## Contribution

It reveals that interstitial polymers can eliminate boundary scattering and increase thermal conductivity in disordered nanoparticle systems, challenging previous assumptions.

## Key findings

- Polymer filling eliminates boundary scattering.
- Thermal conductivity increases with polymer filling.
- Results challenge effective medium theory expectations.

## Abstract

Recent advances in our understanding of thermal transport in nanocrystalline systems are responsible for the integration of new technologies into advanced energy systems, including thermoelectric refrigeration systems and renewable energy platforms. However, there is little understanding of heat energy transport mechanisms that govern the thermal properties of disordered nanocomposites. In this work, we explore thermal transport mechanisms in disordered packings of amorphous nanoparticles with and without a polymer filling the interstices in order to quantify the impact of thermal boundary scattering introduced at nanoparticle edges in an already amorphous system and within the context of a minimum thermal conductivity approximation. By fitting a modified minimum thermal conductivity model to temperature-dependent measurements of thermal conductivity from 80 K to 300 K, we find that the interstitial polymer {\it eliminates} boundary scattering in the disordered nanoparticle packing, which surprisingly leads to an {\it increase} in the overall thermal conductivity of the disordered nanoparticle thin-film composite. This is contrary to our expectations relative to effective medium theory and our understanding of a minimum thermal conductivity limit. Instead, we find that a stiff interstitial material improves the transmission of heat through a nanoparticle boundary, improving the thermal properties of disordered nanoparticle packing. We expect these results to provide insight into the tunability of thermal properties in disordered solids that exhibit already low thermal conductivities through the use of nanostructuring and vibrational thermal bridging.