CAREER: Engineering Heat Conduction Through Alloys and Interfaces

职业：通过合金和界面进行热传导工程

• 批准号: 1554050
• 负责人: Asegun Henry
• 金额: $ 50万
• 依托单位: Georgia Tech Research Corporation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-03-01 至 2020-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1554050&HistoricalAwards=false
• 关键词: CAREER; Engineering; Heat; Conduction; Through

The research objective in this project is to use atomistic level modeling techniques to understand heat conduction through alloys and interfaces and then use the insights gained, to guide the design or identification of materials/systems with unprecedented properties. The educational objective is to increase scientific literacy around atomic level vibrations/heat transfer, since heat transfer plays a fundamental role in our energy infrastructure. The educational approach is to create a new program targeted at underrepresented minority high school students that stimulates a fascination with atomic level vibrations/heat transfer via sonification of MD simulation data (e.g., the conversion of atomic vibrations into audible sounds), which will then be used to make music. The outreach program will recruit African-American and women undergraduates, high school music teachers and high school students each summer, via two outreach programs administered by the Georgia Tech center for education. The participants will build an understanding of both atomic motions and coding as they work together to create a mobile app. The students and general public users will use the mobile app to make music from the sounds generated by sonification of each element on the periodic table, which will provide a new way for students to learn chemistry. The program will facilitate long term mentoring relationships between the PI and participants, which will both strengthen and diversify the underrepresented minority STEM pipeline.Heat conduction through non-electrically conductive media is dominated by the energy transferred between atoms due to their motions. In solids, these motions are vibrations, referred to as phonons, and virtually all knowledge of phonon heat conduction is understood through what is termed the phonon gas model (PGM). The PGM works well in many situations, but the idea itself breaks down in disordered materials, where one cannot rigorously define phonon velocities. Recently, the PI developed a new molecular dynamics (MD) based formalism that presents an alternative picture to the PGM, where transport is described by normal mode correlation, instead of phonon quasi-particle scattering. Most importantly, the new formalism provides a more general view of phonon transport that allows one to treat any class of materials and exploit new features that are inconceivable from the PGM perspective.Leveraging this new perspective, the proposal focuses on (1) studying semiconductor and insulator alloys to understand heat conduction through non-propagating vibrational modes. The purpose of this is to determine if it is possible to identify or engineer an alloy that has higher thermal conductivity than one of its constituent pure crystalline compounds. Such a material would be unprecedented, because the current theory suggests this is impossible, yet experimental data and predictions based on the PI?s new formalism suggest otherwise. (2) The proposal also focuses on studying semiconductor and insulator interfaces to understand the roles of different types of vibrational modes and find the most useful descriptor that can be used to identify/engineer highly conductive interfaces. The purpose of this is to determine if it is possible for an interface to have a conductance higher than the PGM limit, where one simply assumes all vibrational modes transmit 100% of their energy. Exceeding the PGM limit would be unprecedented, because the current theory says it is impossible, yet new experimental data and predictions by the PIs new formalism suggest it is. If thermal interface conductances beyond the PGM limit and alloys with thermal conductivities higher than their pure compounds can be achieved, it could have a major impact on energy applications involving heat dissipation, such as multi-junction solar cells, LEDs and power electronics.

该项目的研究目标是使用原子水平建模技术来了解合金和界面的热传导，然后使用所获得的见解来指导具有前所未有的性能的材料/系统的设计或识别。我们的教育目标是提高有关原子水平振动/热传递的科学素养，因为热传递在我们的能源基础设施中扮演着基本的角色。教育方法是创建一个新的计划，针对未被充分代表的少数族裔高中生，通过将MD模拟数据发声(例如，将原子振动转换为可听声音)来激发对原子级振动/热传递的兴趣，然后将其用于制作音乐。该外展计划每年夏天将通过佐治亚州理工学院教育中心管理的两个外展项目，招募非裔美国人和女性本科生、高中音乐教师和高中生。参与者将在共同创建移动应用程序的过程中，建立对原子运动和编码的理解。学生和普通公众用户将使用这款手机应用程序，将元素周期表上每种元素发声产生的声音制作成音乐，这将为学生提供一种学习化学的新方法。该计划将促进PI和参与者之间的长期指导关系，这将加强和多样化代表不足的少数STEM管道。通过非导电介质的热传导由原子之间由于运动而转移的能量主导。在固体中，这些运动是振动，称为声子，几乎所有关于声子热传导的知识都是通过所谓的声子气体模型(PGM)来理解的。PGM在许多情况下都工作得很好，但这个想法本身在无序材料中就失效了，在无序材料中，人们无法严格定义声子速度。最近，PI发展了一种新的基于分子动力学(MD)的形式，它给出了PGM的另一种图景，其中输运用简正模关联来描述，而不是声子准粒子散射。最重要的是，新的形式主义提供了对声子输运的更一般的看法，允许人们处理任何一类材料并利用从PGM角度无法想象的新特征。利用这一新的视角，该提议集中于(1)研究半导体和绝缘体合金，以了解通过非传播振动模式的热传导。这样做的目的是确定是否有可能识别或设计一种导热系数高于其组成的纯晶体化合物的合金。这样的材料将是史无前例的，因为目前的理论表明这是不可能的，但基于皮涅利？S新形式主义的实验数据和预测表明情况并非如此。(2)该提案还侧重于研究半导体和绝缘体界面，以了解不同类型的振动模式的作用，并找到可用于识别/设计高导电性界面的最有用的描述符。这样做的目的是为了确定界面是否有可能具有高于PGM极限的电导，在这种情况下，人们简单地假设所有振动模式都传输100%的能量。超过PGM限制将是史无前例的，因为目前的理论认为这是不可能的，但新的实验数据和PI新形式主义的预测表明它是不可能的。如果能够获得超过PGM极限的热界面导，以及导热系数高于其纯化合物的合金，可能会对涉及散热的能源应用产生重大影响，如多结太阳能电池、LED和电力电子产品。