Radiation heat transfer during hypersonic flight: A review of emissivity measurement and enhancement approaches of ultra‐high temperature ceramics

Abstract

Emissivity as a function of wavelength, direction, and temperature correlates to a material's efficiency in radiating thermal energy. Knowledge of emissivity is essential for designing and developing radiation-cooled thermal protective systems for hypersonic applications. It is desirable to achieve a high emissivity (with a value close to 1) to maximize heat radiation from a hot surface of a hypersonic vehicle's leading edge during atmospheric re-entry. With the goal of providing the hypersonic materials community with this necessary knowledge, this article offers a basic understanding of thermal radiation, methods for measuring emissivity at high temperatures, and a comprehensive overview of the emissivity of ultra-high temperature ceramics.

Short-Term Oxidation of HfB2-SiC Based UHTC in Supersonic Flow of Carbon Dioxide Plasma

“…The average spectral emissivities in the spectral ranges from 0.8 to 1.0 µm (λ 1 ) and from 2.0 to 2.6 µm (λ 2 ) were evaluated by comparison with the spectral-ratio pyrometer readings as a reference (Figure 5). The idea and details of such in situ emissivity measurements are described in [23,[49][50][51]. Spectral emissivities for both spectral ranges decrease during exposure from a value of 0.64-0.67 to 0.41 due to surface oxidation.…”

Feasibility research of perovskite‐type PrAlO3+δ as high‐temperature infrared radiation coating

“…Notable examples include spinels, [8][9][10][11][12] magnetoplumbitetype hexa-aluminates, 13,14 chromates, 15,16 and carbides. 17 Zeng et al have prepared HfO 2 -based high infrared emissivity coating above 0.87 at 1600 • C by reducing the energy band gap for materials. 18 Dong et al explored La 2 Ce 2 O 7 inner mechanisms and increased the infrared emissivity of La 2 Ce 2 O 7 -based coatings above 0.9 at 1000 • C. 19 In contrast to the aforementioned investigations, perovskite-type (ABO 3 ) materials characterized by simpler lattice structure and unique electronic structure, present a promising avenue for the development of thermal protective coating.…”

“…At present, an array of materials exhibiting elevated emissivity values suitable for high‐temperature coating application has been explored. Notable examples include spinels, 8–12 magnetoplumbite‐type hexa‐aluminates, 13,14 chromates, 15,16 and carbides 17 . Zeng et al.…”