Session: Research Posters

Paper Number: 120164

120164 - Thermal Transport in Embedded Nanoparticle Composites: A Molecular Dynamics Study of the Optimal Size Distribution 

Nanoparticles embedded within a crystalline solid serve as impurity phonon scattering centers that reduce lattice thermal conductivity, a desirable result for thermo-electric applications as the energy conversion efficiency is inversely proportional to the lattice thermal conductivity. Most studies of thermal transport in nanoparticle-laden composite materials have assumed the nanoparticles to possess a single size. If there is a distribution of nanoparticle sizes, how is thermal conductivity affected? Moreover, is there a best nanoparticle size distribution to minimize thermal conductivity? The latter question has been briefly addressed in the literature by a numerical calculation of the thermal conductivity of a nanoparticle-laden semiconductor composite, however, the authors employed a non-mode-resolved phonon-nanoparticle scattering rate expression that is derived from a simplistic analytical treatment of phonons as electromagnetic waves. While conceptually illustrative, we argue this simplified analysis provides little confidence to describe the true effect of nanoparticle size distribution on thermal transport. In this work, we study the thermal conductivity of nanoparticle-laden composites through a molecular dynamics approach which naturally captures anharmonic phonon scattering behavior to the atomic-level more rigorously than analytical theory. From non-equilibrium thermal transport simulations of systematic variety of nanoparticle configurations, we empirically formulate how the factors of nanoparticle size distribution, particle number density, and volume fraction affect the lattice thermal conductivity. We particularly focus on comparison of the computed thermal conductivities of both rational and irrational designed size distributions to the conductivities of the random alloy limit and configurations where the nanoparticles possess a single size. We find at low volume fractions below ~7%, the particle number density is by far the most impactful parameter on thermal conductivity and at fractions above 7%, the effect of the size distribution and number density is minimal compared to the volume fraction. In fact, upon comparisons of configurations with the same particle number density and volume fractions, the nanostructure thermal conductivity of a single nanoparticle size can be lower than that of a size distribution which contradicts intuitions that a single size would attenuate phonon transport less than a spectrum of sizes. The random alloy, which can be considered as a single size configuration in the limit of infinite particle number density, is shown to be the most performant in thermal conductivity reduction. We thus conclude that nanoparticle size distribution only plays a minor role in affecting lattice thermal conductivity with the particle number density and volume fraction being more significant factors that should be considered in fabrication of low-cost nanoparticle-laden composites for potential improved thermo-electric performance.

Presenting Author: Theodore Maranets University of Nevada, Reno

Presenting Author Biography: Theodore is a graduate student pursuing his doctoral degree in mechanical engineering at the University of Nevada, Reno, joining the program in the Fall of 2021. His research primarily focuses on computational modeling of phonon wave transport through nanostructured crystals.

Authors:

Theodore Maranets University of Nevada, Reno
Yan Wang University of Nevada, Reno