【百家大讲堂】第197期：大气再入条件下的新型光子保护系统

　　讲座题目：大气再入条件下的新型光子保护系统 

　　报  告 人：Valery Shklover

　　时  　 间：2019年5月22日 上午8:30-10:30

　　地　   点：5号教学楼502-1 

　　主办单位：研究生院、材料学院

　　报名方式：登录北京理工大学微信企业号---第二课堂---课程报名中选择“【百家大讲堂】第 期：大气再入条件下的新型光子保护系统 ”

 

【主讲人简介】

 Valery Shklover,苏黎世联邦理工学院教授，ETH-NASA大气再入保护涂层项目主管，该项目致力于光子保护涂层的设计与模拟，以及太阳能吸收器的设计。除此以外，Valery Shklover教授的研究领域覆盖广泛，包括热防护涂层、传热学、固态化学、薄膜材料、纤维材料、光子学、超材料、纳米结构等、多孔材料等，现已在400多个同行评审出版物上发表学术文章，拥有9项专利。

主讲人简介（英文）

Dr. Valery Shklover has started to work on design and simulation of photonic protective coatings and spectrum splitting for solar photovoltaics. After 2015 Valery Shklover is project coordinator at the Institute of Electromagnetic Fields of the Department of Electrical Engineering and Information Technology of the ETH Zurich, where he is concentrating on the ETH-NASA projects on protection coatings for atmospheric re-entry. He was also supervisor of two PhD works on photonic thermal protective coatings for atmospheric re-entry (his PhD student got ETH medal) and on solar absorbers. 

The main scientific interests of Dr. Valery Shklover comprise thermal protective coatings, thermal conductivity modeling, heat transfer, solid-state chemistry, thin films fabrication and properties, fiber materials, photonics, application of correlation function approach to determination materials properties, texture, metamaterials, nanostructures, porous materials, sensors. V. Shklover is author of more than 400 peer-reviewed publications, he owns 9 patents.

 

 

【讲座信息】

光子热保护系统（pTPS）可用于在大气重返大气层时对航天器进行保护，当极高的进入速度导致强烈的电磁辐射时，这种辐射（与对流和催化加热结合）可导致飞行器表面严重过热。对于月球返回轨道，激波层中电离气体的电磁辐射可占总热通量的30-50%；对于木星返回轨道，99%的热量是辐射性的。pTPS的设计可以调整到特定行星的辐射光谱以及特定的进入条件。pTPS的组成材料应满足一些严格要求，如高温稳定性、低吸收率、抗氧化性等。需要电介质对比度，允许全向pTPS的设计。本次讲座中，将讲解反射强电磁辐射的各种光子结构，包括层状结构、逆蛋白石结构、木桩结构、多孔反射层、编织结构、导模共振反射层等。本次讲座中将详细讲解对由玻璃碳（GC）和碳化硅组成的光子结构进行了近红外辐射光谱的优化。与SiC相比，由于材料吸收，GC结构的反射率限制在约38%。然而，GC可以设计为相对较高的单频反射~80%。光子前体的制备，可将它们可控地作为添加剂整合到目前由NASA多孔浸渍碳烧蚀器使用（形成光子复合物），并且最终测试遵循光子前体的理论研究基础。此外，讲座中将提出考虑制造不精确性对光子结构反射率的影响的方法，即可以通过蒙特卡罗射线追踪（MCRT）模拟来分析光子添加剂的整合方式，和实现光子复合材料的预期反射率估计。

内容简介（英文）

The photonic thermal protective systems (pTPS) can be used for protection of space vehicles during atmospheric re-entry, when extremely high entry velocities lead to strong electromagnetic radiation, which (combined with convective and catalytic heating) can cause undesirable heating of vehicle's surface. Electromagnetic radiation from the ionized gas in the shock layer can constitute up to 30-50% of the overall heat flux for lunar return trajectories, albeit for relatively short times. For Jupiter entries 99% of the heating is radiative. The pTPS design can be tuned to the radiative spectra of a specific planet as well as to the specific entry conditions. The constituent pTPS materials should meet a number of the strict requirements to re-entry application, such as high-temperature stability, low absorptivity, oxidation resistance and others. Dielectric contrast is required, permitting the design of omnidirectional pTPS. In this work, various photonic structures for reflecting strong electromagnetic radiation are proposed and optimized, including layered structures, inverse opals, woodpiles, porous reflectors, woven structure, guided mode resonance reflectors. For example, photonic structures composed of glassy carbon (GC) and silicon carbide were optimized for near-infra-red part of radiative spectra. The reflectivity of GC structures, in contrast to SiC, is limited to ~38%, due to material absorption. Nevertheless, GC can be designed for a relatively high single-frequency reflection ~80%. Fabrication of photonic precursors, controlled integration them as additives into currently used by NASA porous impregnated carbon ablators (resulting in formation of photonic composites) and final testing follow the theoretical studies of photonic precursors. The method to take into account the influence of fabrication inaccuracies onto reflectivity of photonic structures is suggested. The way of integration of photonic additives and estimation of expected reflectivity of photonic composites can be analysed by the Monte Carlo Ray Tracing (MCRT) simulations.