Thermal Rectification Enabled by Nanoscale Radiative Heat Transfer

CBET-1235975PI：张固态热整流器近年来备受关注，因为控制热流方向对于热管理和能量收集应用至关重要。虽然大多数固态热整流器是基于界面附近材料的非线性声子、电子或机械性质，但光子器件可能有利于在较宽的温度范围内获得较大的整流因子。结果表明，近场热辐射可以达到超过Stefan-Boltzmann定律所预测的热流密度，而Stefan-Boltzmann定律是普朗克黑体辐射理论所规定的常规极限。由于其在近场传感和热成像、纳米制造和热光电器件等方面的应用前景，近年来受到了人们的广泛关注。该项目将使用具有变温介电功能的不同材料来加强真空热整流。这项研究的一个创新方面是使用聚合物垫来创造亚微米级的真空间隙，同时减少热传导。这将使得能够明确地确定通过大片区域的近场辐射传输。还将对有希望的材料在高温下的光谱辐射性能进行测量，以阐明纳米级辐射热传输所介导的热整流的潜在机制。测量大面积之间的纳米级热辐射仍然是一个令人生畏的挑战。这项研究将为真空热整流器提供实验演示。研究高温下的辐射特性以及它们如何影响近场辐射传输将使人们能够更深入地了解光子与物质的相互作用。这项研究的成功将促进使用近场热辐射的其他一些应用，包括用于能量收集的近场热光伏系统。这一项目有望带来理论和实验上的进步。研究成果将广泛传播到多学科期刊和会议上。该项目将对工程教育产生重大影响。从事这个项目的学生将获得热辐射基础理论的知识，以及微/纳米制造和热/光学仪器的经验。将积极招募代表人数不足的学生参与这项研究，并鼓励他们攻读高级工程学位。此外，研究成果将被纳入一本关于热辐射的新的研究生教科书。

CBET-1235975PI: ZhangSolid-state thermal rectifiers have received much attention in recent years, because controlling the direction of heat flow is critically important for thermal management and energy-harvesting applications. While most solid-state thermal rectifiers are based on the nonlinear phononic, electronic or mechanical properties of materials near the interfaces, a photonic device may be advantageous for obtaining large rectification factors over a broad temperature range. It has been shown that near-field thermal radiation can achieve a heat flux exceeding that predicted by the Stefan-Boltzmann law, which is the conventional limit set forth by Planck's blackbody radiation theory. Much attention has been paid to this research area lately, due to its promising applications in near-field sensing and thermal imaging, nanomanufacturing, and thermophotovoltaic devices. This project will use dissimilar materials with temperature-dependent dielectric functions to enhance vacuum thermal rectification. An innovative aspect of this research is the use of polymer pads to create sub-micrometer vacuum gaps with reduced heat conduction. This will allow the unambiguous determination of near-field radiative transfer through large areas. Measurements of the spectral radiative properties of promising materials at elevated temperatures will also be performed to elucidate the underlying mechanisms of thermal rectification mediated by nanoscale radiative heat transfer. Measurements of nanoscale thermal radiation between large areas remain a daunting challenge. This research will provide an experimental demonstration of a vacuum thermal rectifier. The study of the radiative properties at high temperatures and how they can affect near-field radiative transfer will enable a deeper understanding of photon-matter interactions. The success of this research will facilitate a number of other applications that use near-field thermal radiation, including near-field thermophotovoltaic systems for energy harvesting. Both theoretical and experimental advances are expected to result from this project. The research findings will be broadly disseminated to multidisciplinary journals and conferences. This project will make a significant impact on engineering education. Students working on this project will gain knowledge in the fundamental theory of thermal radiation as well as experience in micro/nanofabrication and thermal/optical instrumentation. Underrepresented students will be actively recruited to participate in this research as well as encouraged to pursue advanced engineering degrees. Furthermore, the research results will be integrated in a new graduate textbook on thermal radiation.