Temperature-dependent thermal conductivity in nanoporous materials studied by the Boltzmann Transport Equation

Abstract

Nanostructured materials exhibit low thermal conductivity because of the additional scattering due to phonon-boundary interactions. As these interactions are highly sensitive to the mean free path (MFP) of a given phonon mode, MFP distributions in nanostructures can be dramatically distorted relative to bulk. Here we calculate the MFP distribution in periodic nanoporous Si for different temperatures, using the recently developed MFP-dependent Boltzmann Transport Equation. After analyzing the relative contribution of each phonon branch to thermal transport in nanoporous Si, we find that at room temperature optical phonons contribute 18 % to heat transport, compared to 5% in bulk Si. Interestingly, we observe a steady thermal conductivity in the nanoporous materials over a temperature range 200 K < T < 300 K, which we attribute to the ballistic transport of acoustic phonons with long intrinsic MFP. These results, which are also consistent with a recent experimental study, shed light on the origin of the reduction of thermal conductivity in nanostructured materials, and could contribute to multiscale heat transport engineering, in which the bulk material and geometry are optimized concurrently.

References in corpus (3)

• Significant reduction of lattice thermal conductivity by electron-phonon interaction in silicon with high carrier concentrations: a first-principles study
• Coherent and Incoherent Thermal Transport in Nanomeshes
• Toward phonon-boundary engineering in nanoporous materials

Cited by in corpus (9)

• First-principles dynamics of electrons and phonons
• Atomistic S-matrix method for numerical simulation of phonon reflection, transmission and boundary scattering
• Phonon Bottleneck Identification in Disordered Nanoporous Materials
• Achieving Minimal Heat Conductivity by Ballistic Confinement in Phononic Metalattices
• Heat current anticorrelation effects leading to thermal conductivity reduction in nanoporous Si
• Thermal Anisotropy Enhanced by Phonon Size Effects in Nanoporous Materials
• Theory of the Dynamical Thermal conductivity of Metals
• Enhanced Thermoelectric Performance of Polycrystalline Si0.8Ge0.2 Alloys through the Addition of Nanoscale Porosity
• Computational generation of voids in $a$-Si and $a$-Si:H by cavitation at low density