Progress in the understanding of heat transfer in nanocomposites

CNRS researchers have highlighted an unexpected impact of the microstructure of a nanocomposite material on its ability to transport heat. This new knowledge, published in the journal Nanoscale, could benefit applications requiring thermal control such as the conversion of heat into electricity.

Due to the current energy requirements, controlling heat is a major societal challenge. This new study provides a significant understanding of thermal transport in nanocomposite materials. This work, based on numerical simulations involving molecular dynamics, was carried out by researchers from the Centre for Energy and Thermal Sciences of Lyon (CETHIL, CNRS / INSA Lyon / University Claude Bernard Lyon 1), the Institut Lumière Matière (ILM, CNRS / University Claude Bernard Lyon 1) and the Laboratory of energy and theoretical and applied mechanics (LEMTA, CNRS / University of Lorraine). The researchers focused on a nanocomposite made of a thermally insulating silica matrix in which they introduced nanograins forming a thermally conductive crystalline structure of galium nitride (GaN). At small scales, heat is associated with the vibrations of atoms called phonons.

The study shows that a small amount of GaN (5%) is sufficient to generate a significant heat flow within the material. Indeed, this ordered structure promotes a tunneling effect of the phonons through the silica and thus the heat transport from one nanoparticle to another. This surprising result goes against the behavior predicted by the laws of physics at the macroscopic scale. Thus, by changing the organization and orientation of the nanoparticles, the thermal conductivity of the material can be controlled at will. This discovery could be used for technological applications for which better heat dissipation is targeted, but also for thermoelectric applications, for which heat transport needs to be inhibited.

This study is the subject of a press release from CNRS: 
https://insis.cnrs.fr/fr/cnrsinfo/avancee-majeure-de-la-comprehension-des-transferts-de-chaleur-dans-les-nanocomposites