Controlling and Understanding Thermal Energy Exchange at Single Domains of Functional Materials

控制和理解功能材料单域的热能交换

• 批准号: 1608899
• 负责人: Junqiao Wu
• 金额: $ 40万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-01 至 2020-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1608899&HistoricalAwards=false
• 关键词: Controlling; Understanding; Thermal; Energy; Exchange

NON-TECHNICAL DESCRIPTION: Heat has been familiar and important to humankind for a much longer history than electricity, yet people's ability of controlling and understanding heat lags much behind that of electricity. The key lies in materials science and engineering: how to design, synthesize and develop materials and tools that support, direct and gauge heat flow (in the same manner in which semiconductors work with electric current). This project seeks to tackle this fundamental problem using a specific class of materials: nanoscale functional materials. As heat is carried by both electrons and atomic vibration (the so-called "phonons"), achieving this goal requires exquisite control of behavior of both electrons and phonons, as well as their interactions. Functional materials made in the nanoscale and with high quality allow such control because they can be used to regulate the direction and magnitude of heat flow (as well as its conversion from/to electric current and fields). Knowledge gained in this project is used to educate underrepresented students through a partnership between Prof. Wu's university and local middle-high schools. TECHNICAL DETAILS: Functional materials support extraordinary thermal energy exchange processes such as thermoelectrics, thermal rectification, and electrocaloric effect. Domains (including functional domains and crystal grains) and domain walls of various types ubiquitously exist in these materials and strongly influence, sometimes dominate, the thermal energy exchange processes. Hampered by challenges in measuring heat flow at the nanoscale, previous studies of these effects are mostly limited to materials with a large number of disordered domains. As a result, intrinsic effects are hidden by ensemble averaging over the domains, leaving many key questions unsettled. This project goes beyond this ensemble averaging, to gauge, understand, control and optimize the thermal energy exchange at the level of single domain or single domain wall of functional materials, using microfabricated tools and nanomaterials processing techniques recently developed in Prof. Wu's lab. The project enables exquisite control of heat flow with functional materials by engineering density and mobility of electrons as well as crystallinity and interface of the lattice; identifies fundamental limits in such thermal energy exchange processes as interfacial thermal rectification, composite thermoelectrics, and electrocaloric cooling; and opens tremendous opportunities for novel design and improved performance of various thermal devices. Integrated with the research activities, Prof. Wu is also running an education project that stimulates and prepares pre-college students for careers in materials science and engineering pertaining to thermal applications.

非技术描述：热对人类来说是熟悉和重要的，比电的历史要长得多，但人们控制和理解热的能力远远落后于电。关键在于材料科学和工程：如何设计、合成和开发支持、引导和测量热流的材料和工具（与半导体与电流工作的方式相同）。这个项目试图用一种特殊的材料来解决这个基本问题：纳米级功能材料。由于热量由电子和原子振动（所谓的“声子”）携带，实现这一目标需要对电子和声子的行为以及它们之间的相互作用进行精确的控制。纳米级和高质量的功能材料允许这样的控制，因为它们可以用来调节热流的方向和大小（以及从电流和场到电流和场的转换）。在这个项目中获得的知识将通过吴教授所在的大学和当地中学的合作来教育弱势学生。技术细节：功能材料支持非凡的热能交换过程，如热电、热整流和电热效应。各种类型的畴（包括功能畴和晶粒）和畴壁普遍存在于这些材料中，并强烈影响，有时甚至主导着热能交换过程。由于在纳米尺度上测量热流的挑战，先前对这些效应的研究大多局限于具有大量无序畴的材料。其结果是，内在效应被域上的整体平均所掩盖，留下了许多悬而未决的关键问题。该项目超越了这种整体平均，利用吴教授实验室最近开发的微加工工具和纳米材料加工技术，测量、理解、控制和优化功能材料单畴或单畴壁水平上的热能交换。该项目通过工程密度和电子迁移率以及晶格的结晶度和界面，实现功能材料热流的精细控制；识别诸如界面热整流、复合热电和电热冷却等热能交换过程的基本限制；并为各种热器件的新设计和改进性能提供了巨大的机会。与研究活动相结合，吴教授还开展了一个教育项目，旨在激励和培养大学预科学生从事与热应用相关的材料科学和工程方面的职业。