Phonon Transport within Periodic Porous Structures -- From Classical Phonon Size Effects to Wave Effects

TL;DR

This paper reviews how periodic porous structures influence phonon transport, highlighting classical size effects and wave interference phenomena, with implications for thermal management at various temperatures.

Contribution

It provides a comprehensive comparison of theoretical and experimental studies on phonon transport in periodic nanostructures, emphasizing the transition from classical to wave effects.

Findings

Classical size effects dominate at room temperature, reducing thermal conductivity.

Wave interference effects are significant mainly at ultralow temperatures (~10 K).

Periodic nanostructures can be engineered to tailor thermal properties.

Abstract

Tailoring thermal properties with nanostructured materials can be of vital importance for many applications. Generally classical phonon size effects are employed to reduce the thermal conductivity, where strong phonon scattering by nanostructured interfaces or boundaries can dramatically supress the heat conduction. When these boundaries or interfaces are arranged in a periodic pattern, coherent phonons may have interference and modify the phonon dispersion, leading to dramatically reduced thermal conductivity. Such coherent phonon transport has been widely studied for superlattice films and recently emphasized for periodic nanoporous patterns. Although the wave effects have been proposed for reducing the thermal conductivity, more recent experimental evidence shows that such effects can only be critical at an ultralow temperature, i.e., around 10 K or below. At room temperature, the impacted phonons are mostly restricted to hypersonic modes that contribute little to the thermal conductivity. In this review, the theoretical and experimental studies of periodic porous structures are summarized and compared. The general applications of periodic nanostructured materials are further discussed.