CAREER: Engineering Thermal Energy Transport Using Embedded Nanoparticles

利用嵌入纳米粒子的工程热能传输本项目探索了含有嵌入颗粒的材料中的热传输的基本物理。许多材料中的热流是由称为声子的随机振动产生的，这种随机振动以波状的方式传输能量。声子与他们遇到的任何杂质相互作用，包括粒子，可能导致能量散射，阻碍热量流动。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颗粒相互作用，并利用这些信息来设计具有改善热性能的材料。该项目的科学发现可能导致纳米结构电子和光学材料具有更好的散热能力，以及热电材料以前所未有的效率直接将热转化为电，反之亦然。该项目还寻求对社会产生更广泛的影响，包括(1)与4Young Production非营利组织合作实施一项教育推广计划，让德州威尔明顿的高危K-8儿童接触光学、热传递和能源节约；(2)实施一项针对工业用户的教育推广计划，目的是将超快温度测量技术转移给非学术最终用户。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远超过先前认识的，这改变了纳米复合材料热控制的几何和材料设计规则，以及(2)局域化可能支配对致密纳米合金材料中的热传输至关重要的长波声子的物理。利用连续介质力学的精确结果，该项目探索了与在米氏散射系统中操作相关的复杂干扰效应如何改变设计策略，如试图控制热传输时纳米颗粒大小、成分和形状的选择。一种新发展的原子计算方法被用来提供任意几何形状下与偏振和波数相关的声子散射截面，并与声子-声子和声子-合金散射率的第一性原理计算相结合来预测逐模的热输运性质；该方法将使模拟前所未有的尺寸的声子-结构散射问题成为可能，我们用该方法来研究致密纳米复合材料中声子局域化的物理。通过对纳米合金颗粒材料进行相应的热传输测量，该项目寻求三维声子局部化的实验证据和理解。

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.