Tunable Super-Planckian Near-field Radiative Heat Transfer with Thermochromic Metamaterials

在零开尔文以上的有限温度下，材料可以发射与常规热辐射相关的长距离传播的电磁波，热通量受到黑体的限制，以及当距离远小于特征热波波长时，在近距离辐射热通量可能超过黑体极限数量级的衰减波。本项目研究颜色随温度变化的热致变色材料的可调谐近场辐射热输运。该项目可能会影响许多潜在的能源应用，包括微电子的热管理和固态热电发电中的能量转换。它还将为主动热控制、热电路和热计算机等基于辐射的近场设备铺平道路。研究成果将通过期刊出版物、会议报告和课程教学进行传播。国际和平研究所将为下一代劳动力培训研究人员和领导人，强调代表不足的群体的更广泛参与。研究生将学习多学科的基础知识和技能。亚利桑那州立大学富尔顿本科生研究计划为本科生提供了一个很好的机会，让他们参与PI实验室的研究活动。PI将吸引当地的K-12学生，并通过亚利桑那州立大学的各种项目接触当地公众和社会。该研究项目旨在促进对热致变色超材料在纳米真空间隙中的可调谐近场辐射热传输的基本理解，基于不同的物理机制，超普朗克热流超过黑体极限。二氧化钒作为一种独特的热致变色材料，当其温度升高到68°C以上时，可以经历绝缘体到金属的相变。基于涨落电动力学和薄膜单轴波光学的理论计算以及基于严格耦合波分析的数值模拟将用于预测不同热致变色纳米结构的光谱和总辐射热流。包括薄膜沉积、深紫外光刻和电子束光刻在内的先进纳米制造方法将被用来制备所设计的热致变色纳米结构，而独特的技术如随温度变化的红外光谱将被用来表征所制备的样品的辐射热性能。可以实现100 nm真空间隙的新型近场热计量技术将被用于近场辐射换热的实验研究，以了解不同的物理机制如何使不同的热致变色纳米结构的相变时的热流密度可调。该奖项反映了NSF的法定使命，通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Materials at finite temperature above zero Kelvin can emit propagating electromagnetic waves over long distances related to conventional thermal radiation with heat flux limited by blackbodies, as well as decaying waves in close proximity where radiative heat flux could exceed the blackbody limit by orders of magnitude when the distance is much smaller than the characteristic thermal wavelength. This project studies tunable near-field radiative thermal transport with thermochromic materials whose color changes with temperature. The project could impact many potential energy applications including thermal management of microelectronics and energy conversion in solid-state thermopower generation. It will also pave the way to radiation-based near-field devices for active heat control, thermal circuits and thermal computers. The research outcomes will be disseminated through journal publications, conference presentations and course teaching. The PI will train researchers and leaders for the next generation of work force, emphasizing on broader participation of underrepresented groups. Graduate students will learn the fundamentals and skills of multiple disciplines. The Arizona State Fulton Undergraduate Research Initiative program offers a great opportunity for undergraduate students to participate in the research activities in the PI’s lab. The PI will engage local K-12 students and reach out to local public and society through various programs at ASU.This research project aims to advance the fundamental understanding in tunable near-field radiative thermal transport with thermochromic metamaterials across nanometric vacuum gaps based on different physical mechanisms with super-Planckian heat flux exceeding the blackbody limit. Vanadium dioxide as one unique thermochromic material could experience insulator-to-metal phase transition when its temperature increases beyond 68°C. Theoretical calculations based on fluctuational electrodynamics incorporated with thin-film uniaxial wave optics as well as numerical modeling based on rigorous coupled-wave analysis will be implemented to predict the spectral and total radiative heat flux with different thermochromic nanostructures. Advanced nanofabrication methods including thin-film deposition, deep-UV lithography and electron-beam lithography will be used to fabricate the designed thermochromic nanostructures, while unique techniques such as temperature-dependent infrared spectroscopy will be employed to characterize the radiative thermal properties of fabricated samples. Novel near-field thermal metrology that could achieve down to 100-nm vacuum gaps will be utilized for the experimental study of near-field radiative heat transfer to understand how different physical mechanisms enable the tunable heat flux upon phase transition of different thermochromic nanostructures. Potential applications such as near-field radiative thermal rectification and switching will be experimentally demonstrated.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.