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CAREER: Thermal Transport Studies of Individual Grain Boundaries within Nanostructured Materials

职业：纳米结构材料内单个晶界的热传输研究

基本信息

批准号：
1651840
负责人：
Qing Hao
金额：
$ 50.64万
依托单位：
University of Arizona
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2017
资助国家：
美国
起止时间：
2017-03-01 至 2023-02-28
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1651840&HistoricalAwards=false
关键词：
CAREER Thermal Transport Studies Individual

项目摘要

Thermal Transport Studies of Individual Grain Boundaries within Polycrystalline MaterialsAt the nanoscale, interfaces can strongly restrict heat transfer by scattering the heat carriers, which are mainly phonons in nonmetallic materials. Such interfacial phonon scattering and its resulting interfacial thermal resistance are important to many applications, ranging from the thermal management of nanoelectronic and optical devices, to effective thermal insulation materials, to thermoelectric energy conversion. However, the fundamental understanding of how phonons interact with an interface is still limited after decades of research, especially when the complexities of a real interface are considered. In particular, the thermal resistance of a single grain boundary (GB) has not been directly measured for a polycrystalline bulk material or thin film. Existing thermal studies can only extract an averaged GB thermal resistance by fitting the temperature-dependent thermal conductivity of the whole material. To address this critical issue, this project combines thermal measurements and atomistic simulations to reveal the detailed phonon transport across individual GBs. For general interfaces, the knowledge gained from this project will provide important guidance for tailoring the interfacial phonon transport by varying the interfacial atomic and nanoscale structures. The integrated educational plan aims to involve undergraduate and high-school students, especially those from underrepresented groups, in cutting-edge energy research. Innovative outreach activities also include developing a challenge for middle-school students in the Mathematics, Engineering, Science Achievement program, and demonstrating the importance of nanotechnology research to the general public through museum exhibitions.The objective of the proposed research is to better understand the phonon transport across an individual GB within polycrystalline bulk materials and thin films. The investigations focus on GBs formed by two widely used techniques for materials synthesis, i.e., chemical vapor deposition (CVD) for thin films and hot press for nanostructured bulk materials. Thermal resistance measurements are carried out on a single GB, using nanofabricated thermal sensors to measure the steady-state temperature jump across this GB under a given heat flow. This will provide unprecedented experimental data for phonon transport across single GBs within these polycrystalline materials. As a comparable case of a real GB within hot-pressed bulk materials, planar film-wafer interfaces by hot press are also measured for varied crystal misorientations across the interface. All thermal measurements can be directly compared to predictions based on atomistic Green?s function (AGF) simulations that employ the exact interfacial atomic structure (e.g., dislocations, crystal orientation, roughness, nanoscale strain as atomic displacement) revealed by different microscopy techniques. The integration of individual GB measurements and AGF simulations reaches beyond previous AGF studies that often use guessed interfacial atomic structures and are seldom validated by experiments. Fundamentally, the proposed study will elucidate the relationship between the synthesis condition, interfacial atomic structure, and the corresponding GB thermal transport. The success of this project will significantly advance the thermal studies for many important applications, such as nanoelectronic devices using CVD films and film-wafer bonding, polycrystalline thin-film solar cells, structural and optical bulk materials by hot press, thermoelectric materials, and thermal barrier coatings.

多晶材料中单个晶粒边界的热输运研究在纳米尺度下，界面可以通过散射热载体来强烈地限制热传递，在非金属材料中，热载体主要是声子。这种界面声子散射及其产生的界面热阻对许多应用都很重要，从纳米电子和光学器件的热管理到有效的热绝缘材料，再到热电能量转换。然而，经过几十年的研究，对声子如何与界面相互作用的基本理解仍然有限，特别是当考虑到真实的界面的复杂性时。特别地，对于多晶块体材料或薄膜，还没有直接测量单个晶界（GB）的热阻。现有的热研究只能通过拟合整个材料随温度变化的热导率来提取平均GB热阻。为了解决这个关键问题，该项目结合热测量和原子模拟来揭示单个GB之间详细的声子传输。对于一般的接口，从这个项目中获得的知识将提供重要的指导，定制界面声子输运通过改变界面原子和纳米结构。综合教育计划旨在让本科生和高中生，特别是那些来自代表性不足群体的学生参与尖端能源研究。创新的外展活动还包括在数学、工程、科学成就计划中为中学生开发一项挑战，并通过博物馆展览向公众展示纳米技术研究的重要性。拟议研究的目标是更好地了解多晶块体材料和薄膜中单个GB的声子输运。研究的重点是由两种广泛使用的材料合成技术形成的GB，即，用于薄膜的化学气相沉积（CVD）和用于纳米结构体材料的热压。热阻测量在单个GB上进行，使用纳米制造的热传感器来测量在给定热流下跨越该GB的稳态温度跳变。这将为这些多晶材料中的声子输运提供前所未有的实验数据。作为一个可比较的情况下，一个真实的GB内的热压块体材料，平面薄膜-晶片界面热压也测量了不同的晶体取向差跨越界面。所有的热测量可以直接比较的基础上预测原子绿色？S函数（AGF）模拟，其采用精确的界面原子结构（例如，位错、晶体取向、粗糙度、作为原子位移的纳米级应变）。个别GB测量和AGF模拟的集成超出了以前的AGF研究，通常使用猜测的界面原子结构，很少通过实验验证。从根本上说，拟议的研究将阐明合成条件，界面原子结构，和相应的GB热输运之间的关系。该项目的成功将大大推进许多重要应用的热研究，例如使用CVD薄膜和薄膜-晶片键合的纳米电子器件，多晶薄膜太阳能电池，热压结构和光学块状材料，热电材料和热障涂层。