Thermal Rectification Enabled by Nanoscale Radiative Heat Transfer

Georgia Tech Research Corporation, Atlanta GA

Investigators

Abstract

CBET-1235975 PI: Zhang Solid-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.