Phonon transport in nanostructured materials is critical for thermal management in a wide range of technologies. While defects are typically associated with reduced thermal conductivity, their influence can be more nuanced depending on how they interact with lattice vibrations and mechanical properties. We use classical molecular dynamics simulations to investigate how dislocations, plasticity, and nanostructuring affect phonon-mediated heat transport in a variety of systems.

Our recent study on dislocations challenges the traditional view that they reduce thermal conductivity. Although dislocations act as scattering centers, they also relax stress and increase the contact radius at interfaces between nanoparticles, which can compensate or even outweigh their scattering effect, leading to an overall conductivity increase [1]. Similarly, when examining thermal transport between nanoparticles under compression, we show that plastic deformation modifies the local atomic structure and enhances contact, increasing the interfacial lattice conductivity [2].

In high-entropy alloys, electronic heat conduction is strongly reduced and it is similar to lattice conductivity. Thermal processing can lead to precipitation and chemical short-range order (SRO). Matrix-precipitate interfaces could decrease phonon mean-free paths, but we find that percolation of ordered phases enhances phonon propagation and increases thermal conductivity [3]. Therefore, different synthesis structures might allow conductivity tuning.   

Thermal conductivity of amorphous carbon nanostructures can be understood in terms of phonon transport with short mean free paths. Surprisingly, systems with porosity display higher conductivity than systems without porosity, due to stiffening of the carbon network that leads to higher sound velocity [4]. 

New results for samples with defects, including irradiation defects in Fe, W, and Bi nanowires, related to recent experiments, will also be discussed. 

Together, these findings highlight the complex role of disorder, morphology, and defects in phonon transport, offering new insights and design principles for materials with tunable thermal properties at the nanoscale. 

This work was supported by a PIDIUM 2024 -2026 grant.

References:
[1] Mora-Barzaga, G., Miranda, E. N., & Bringa, E. M. (2023). Int. J. Therm. Sci. 193, 108474. doi.org/10.1016/j.ijthermalsci.2023.108474
[2] Mora-Barzaga, G., Miranda, E. N., & Bringa, E. M. (2024). J. Appl. Phys. 136, 175103. doi.org/10.1063/5.0225591
[3] Mora-Barzaga, G. et al. (2024). Sci. Rep. 14, 20628. doi.org/10.1038/s41598-024-70500-9
[4] Mora-Barzaga, G. et al. (2022). Nanomaterials 12, 2835. doi.org/10.3390/nano12162835