Tunable Thermal Transport Characteristics of Nanocomposites.

G P Srivastava,Iorwerth O Thomas

doi:10.3390/nano10040673

Abstract

We present a study of tunable thermal transport characteristics of nanocomposites by employing a combination of a full-scale semi-ab inito approach and a generalised and extended modification of the effective medium theory. Investigations are made for planar superlattices (PSLs) and nanodot superlattices (NDSLs) constructed from isotropic conductivity covalent materials Si and Ge, and NDSLs constructed from anisotropic conductivity covalent-van der Waals materials MoS and WS. It is found that difference in the conductivities of individual materials, period size, volume fraction of insertion, and atomic-level interface quality are the four main parameters to control phonon transport in nanocomposite structures. It is argued that the relative importance of these parameters is system dependent. The equal-layer thickness Si/Ge PSL shows a minimum in the room temperature conductivity for the period size of around 4 nm, and with a moderate amount of interface mass smudging this value lies below the conductivity of SiGe alloy.

Highlights

Thermal conductivity is a property of bulk solids spanning over four orders of magnitude, covering the range 10−1–103 W m−1 K−1 [1] at room temperature
The cross-plane conductivity component κzz for the Si/Ge planar superlattices (PSLs) system decreases as D increases from an ultralow nm value, takes a minimum in the range 3–12 nm, and continues to increase until 10 μm, before saturating to the bulk weighted result obtained from Equation (3)
From investigations made for planar superlattices (PSLs) and nanodot superlattices (NDSLs) constructed from isotropic conductivity covalent materials Si and Ge, and NDSLs constructed from anisotropic conductivity covalent-van der Waals materials MoS2 and WS2, we have identified four key parameters that control thermal transport in nanocomposites

Summary

Introduction

Thermal conductivity is a property of bulk solids spanning over four orders of magnitude, covering the range 10−1–103 W m−1 K−1 [1] at room temperature This range can be further increased by including solids of nanoscale size [1] and even more so through considering nanocomposites. In a review article Dresselhaus et al [8] presented the status of experimental and theoretical works in the emerging field of low-dimensional thermoelectricity, and discussed the outlook for future research directions for nanocomposite thermoelectric materials. In their theoretical works, Hicks and Dresselhaus did not present any numerical calculations of phonon conductivities for the nanostructures they had studied. The identification of key physical parameters of nanostructures, nanocomposites, for tuning phonon transport remains an important topic of both fundamental and practical importance

Methods

Results

Conclusion