CAREER: Engineering Thermal Energy Transport Using Embedded Nanoparticles

工程热能传输使用嵌入纳米粒子本项目探讨热传递的基本物理与嵌入粒子的材料。许多材料中的热流是由随机振动产生的，这种振动被称为声子，它以波状的方式传递能量。声子与它们遇到的任何杂质（包括粒子）相互作用，可能导致阻碍热量流动的能量散射。该项目的目标是利用新的理论、计算和实验技术来了解声子如何与纳米粒子相互作用，并利用这些信息来设计具有更好热性能的材料。这个项目的科学发现可能会导致纳米结构的电子和光学材料具有更好的散热能力，热电材料可以直接将热转化为电，并且具有前所未有的效率。该项目还寻求对社会产生更广泛的影响，包括(1)与非营利组织4Youth Production合作，执行一项教育推广计划，让威尔明顿州面临风险的K-8儿童接触光学、传热和节能；(2)执行一项针对工业用户的教育推广计划，目标是将超快热测量技术推广给非学术终端用户。特别是，该项目探索了两个主要的科学假设：(1)Mie散射对传输的重要性远比之前认识到的要大，这改变了纳米复合材料热控制的几何和材料设计规则；(2)在致密纳米颗粒合金材料中，局部化可能控制对热传输重要的长波声子的物理特性。利用连续介质力学的精确结果，该项目探索了与Mie散射机制相关的复杂干涉效应如何改变设计策略，例如在试图控制热输运时选择纳米颗粒大小、成分和纳米颗粒形状。采用一种新发展的原子计算方法来提供任意几何形状中与极化和波数相关的声子散射截面，并结合声子-声子和声子-合金散射率的第一性原理计算来预测逐模的热输运性质；该方法可以模拟空前规模的声子结构散射问题，用于研究致密纳米复合材料中声子局部化的物理特性。通过对纳米颗粒合金材料进行相应的热输运测量，该项目寻求实验证据和对三维声子定位的理解。

Engineering Thermal Energy Transport Using Embedded NanoparticlesThis project explores the fundamental physics of heat transfer in materials with embedded particles. Heat flow in many materials occurs by random vibrations, called phonons, that transport energy in a wave-like manner. Phonons interact with any impurities they encounter, including particles, potentially leading to energy scattering that impedes the flow of heat. The goal of this project is to leverage new theoretical, computational, and experimental techniques to understand how phonons interact with nanoparticles, and to use that information to engineer materials with improved thermal properties. The scientific findings from this project could lead to nanostructured electronic and optical materials with improved heat dissipation capabilities, and thermoelectric materials that directly convert heat to electricity and vice versa with unprecedented efficiency. The project also seeks to provide a broader impact to society including (1) execution of an educational outreach program in collaboration with the 4Youth Production non-profit organization that exposes at-risk K-8 children in Wilmington, DE to optics, heat transfer, and energy conservation (2) execution of an educational outreach program targeted to industrial users with the goal of transferring ultrafast thermal measurement technology to non-academic end-users. In particular, the project explores two primary scientific hypotheses: (1) that Mie scattering is far more important to transport than previously recognized and this changes the geometric and materials design rules for thermal control of nanocomposites, and (2) that localization may govern the physics of long-wavelength phonons important to thermal transport in dense nanoparticle-in-alloy materials. Using exact results from continuum mechanics, the project explores how complex interference effects associated with operating in the Mie scattering regime alter design strategies such as the choice of nanoparticle size, composition, and nanoparticle shape when trying to control thermal transport. A newly developed atomistic computational method is employed to provide polarization- and wavenumber-dependent phonon scattering cross sections in arbitrary geometries, and integrated with first-principles calculations of phonon-phonon and phonon-alloy scattering rates to predict thermal transport properties on a mode-by-mode basis; the method would enable phonon-structure scattering problems of unprecedented size scale to simulated, which we use to investigate the physics of phonon localization in dense nanocomposites. By performing corresponding thermal transport measurements on nanoparticle-in-alloy materials, the project seeks experimental evidence and understanding of 3-dimensional phonon localization.