CAREER: Investigation of thermal phonon scattering processes in solids

职业：研究固体中的热声子散射过程

• 批准号: 1254213
• 负责人: Austin Minnich
• 金额: $ 40.54万
• 依托单位: California Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-02-01 至 2018-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1254213&HistoricalAwards=false
• 关键词: CAREER; Investigation; thermal; phonon; scattering

1254213MinnichHeat conduction is central to numerous and diverse technologies, ranging from power generation, to electronics, to lasers. Increasingly in these applications, heat conduction occurs at scales much less than a micron, comparable to the fundamental length scales of the heat carriers themselves. For example, nanostructured thermoelectrics may contain engineered structures as small as a few nanometers; these nanoscale materials are 50% more efficient at converting heat to electricity than their macroscopic counterparts. However, further advances are difficult to achieve because of a poor understanding of the lattice vibration, or phonon, scattering processes that largely determine a material?s thermal conductivity. Despite over 50 years of investigation, the mean free paths (MFPs) of phonons, which describe how phonons scatter when they interact with other phonons, defects, and nanostructures, are unknown in most materials. This experimental and computational investigation will provide a comprehensive understanding of thermal phonon scattering. Novel experimental methods that have been developed only recently will be used to measure MFP distributions across length scales ranging from nanometers to millimeters. The effect of different scattering mechanisms on specific phonon modes will be obtained by observing the changes in the MFP distribution as mass defects, grain boundaries, nanoprecipitates, and other nanostructures are systematically introduced into the material. Analytical expressions for the MFPs, which are of great utility to researchers in the field, will be created and validated against the experimental results using numerical solutions of the Boltzmann transport equation. This project will advance our scientific knowledge of heat conduction and enable many applications, particularly in the energy field. Scientifically, the investigation will provide a comprehensive understanding of the complex thermal phonon scattering process, which has eluded scientists for decades, as well as experimentally validate fundamental computational predictions of thermal phonon scattering rates. Practically, this research will enable engineers to design materials with precisely tailored thermal conductivities before fabrication rather than by trial-and-error, a major advance over present capabilities. This ability would lead to many applications, such as highly efficient cars that harvest useful electricity from wasted heat in the tailpipe, environmentally friendly refrigerators that do not use any harmful fluids, and electronic devices with reduced power consumption.

1254213Minnich 热传导是众多不同技术的核心，从发电到电子，再到激光。在这些应用中，热传导越来越多地发生在远小于微米的尺度上，与热载体本身的基本长度尺度相当。例如，纳米结构热电材料可能包含小至几纳米的工程结构；这些纳米级材料将热能转化为电能的效率比宏观材料高 50%。然而，由于对很大程度上决定材料热导率的晶格振动或声子散射过程了解甚少，因此很难取得进一步的进展。尽管经过 50 多年的研究，声子的平均自由程 (MFP)（描述声子与其他声子、缺陷和纳米结构相互作用时如何散射）在大多数材料中仍是未知的。这项实验和计算研究将提供对热声子散射的全面理解。最近开发的新颖实验方法将用于测量从纳米到毫米的长度尺度上的 MFP 分布。当质量缺陷、晶界、纳米沉淀物和其他纳米结构被系统地引​​入材料中时，通过观察 MFP 分布的变化，可以获得不同散射机制对特定声子模式的影响。 MFP 的分析表达式对于该领域的研究人员非常有用，将使用玻尔兹曼输运方程的数值解根据实验结果进行创建和验证。该项目将增进我们对热传导的科学知识，并实现许多应用，特别是在能源领域。从科学角度来看，这项研究将提供对复杂的热声子散射过程的全面理解，该过程几十年来一直困扰着科学家，并通过实验验证热声子散射率的基本计算预测。实际上，这项研究将使工程师能够在制造前设计出具有精确定制热导率的材料，而不是通过反复试验，这是对现有能力的重大进步。这种能力将带来许多应用，例如从排气管中的废热中收集有用电力的高效汽车、不使用任何有害液体的环保冰箱以及功耗更低的电子设备。