Stealth technology enables stealth jets like the F-22, J-20, and Su-57 to efficiently avoid detection by opponent detection systems. This significantly enhances their capacity to survive and strike on the battlefield, making it very significant for national defense security. Microwave and infrared imaging are two crucial technologies used for locking and tracking stealth fighters, which total threat ratio accounts up to 90%. As counter-detection technologies, microwave absorbing material (MAM) and low-infrared emissivity material are crucial for improving the stealth capabilities of fighter aircraft.
Typically, two ways are employed to realize microwave-infrared compatible stealth. One approach is to develop MAM and low infrared emissivity materials separately. Then, applying a layer of the low infrared emissivity coating onto the MAM. However, low infrared emissivity coatings will degrade the microwave absorption performance of the MAM due to the reflection on incident microwave. Another way is to fabricate metamaterial on the surface of MAM. A metamaterial, which possesses a periodic arrangement, is intentionally created to fulfill particular optical features. Typically, it is composed of conductive metals possessing low spectrum emissivity. Through the design of the metamaterial, it is co-optimized between the impedance matching and infrared emissivity properties, resulting in the realization of microwave-infrared compatible stealth. However, the metamaterial shows many drawbacks including complex design, poor oxidation resistance, degradation of performance under high temperature service conditions, and so on. This seriously restricts its practical application. At present, there are few literatures about microwave-infrared compatible stealth performance from the perspective of single material. Combined with principle of electromagnetic loss and ionic conductivity, the 8YSZ coatings as a novel microwave-infrared compatible stealth material is proposed firstly.
Recently, a team of material scientists led by Peng Wu from Kunming University of Science and Technology, China first reported the microwave-infrared compatible stealth performance including permittivity, reflection loss and infrared emissivity of 8YSZ coating. This work not only reports the microwave absorption and infrared stealth performance of 8YSZ coating firstly, but also reveals the principle of electromagnetic loss inside the coating by theoretical simulation and calculation.
The team published their work in Journal of Advanced Ceramics on August 8, 2024.
"In this report, we prepared ZrO2 and 8YSZ coatings by atmospheric plasma spraying technology with corresponding feedstock powder. Then, the phase and microstructure of the prepared coatings are characterized. Compared with ZrO2, 8YSZ has higher lattice symmetry with tetragonal phase because of replacement of Y3+ ions for a portion of Zr4+ in the parent lattice of zirconia, which has an important effect on the high temperature ionic conductivity of 8YSZ coating，" said Peng Wu, research assistant at Faculty of Material Science and Engineering at Kunming University of Science and Technology (China), a young scientist whose research interests focus on the field of thermal protection and stealth function ceramic materials.
"A perfect microwave-infrared compatible stealth material should be composed of simple ingredients, which can not only balance the microwave dissipation and low infrared emissivity but also has a simple prepared process and high operating temperature. Attributed to excellent attributes, the 8 wt% yttria-stabilized zirconia (8YSZ) is widely used in the field of thermal barrier coatings, solid oxide fuel cell, catalysis, gas sensors, medicine and so on. The application of 8YSZ in solid oxide fuel cells is mainly based on its special oxygen ionic conductivity characteristics at high temperatures, and its conductivity can reach about 0.02 S/cm at 800 ℃. Based on free-electron theory, suitable conductivity is conducive to the dissipation of incident microwave, and this implies that 8YSZ may be a promising microwave absorbing material (MAM) especially applied at high temperature." said Peng Wu.
At 900 ℃, 8YSZ possesses excellent microwave absorbing properties including strong absorption (minimum reflection loss (RLmin): -50 dB), thin thickness (1.5 mm), and better effective absorption bandwidth (EAB: 2 GHz). Meanwhile, it maintains low infrared emissivity (ε＜0.3) in the infrared bands of 3-5 μm compared with traditional materials. "Due to the excellent microwave absorbing and infrared stealth performance of 8YSZ coating, it shows great potentials in the filed of microwave-infrared compatible stealth materials," said Peng Wu.
However, more delicate research works are still needed to explore the suitability of 8YSZ as a new microwave--infrared compatible stealth material. In this regard, Wu also put forward three major development directions may be pursued in future works including the thermal shock properties, stability during plasma deposition, and thermal/structural stability of the coatings during performance.
Other contributors include Jun Wang, Zifang Zhao, Jianyu Li from the Faculty of Material Science and Engineering at Kunming University of Science and Technology in Yunnan, China; Wenting He from School of Materials Science and Engineering at Beihang University; Yongpan Zeng, Yanjun Sun, Xiangwei Tang from Guangdong Midea Kitchen Appliances Manufacturing Co., Ltd., Midea Group.
This work was supported by the National Natural Science Foundation of China (No. 52402078), Yunnan Major Scientific and Technological Projects (No. 202302AG050010), Yunnan Fundamental Research Projects (No. 202201BE070001-008), and the National Key Research and Development Program of China (No. 2022YFB3708600). The author (Wenting He) appreciates the support from the Youth Talent Support Program of Beihang University.
About Author
Peng Wu holds a Ph.D. in ceramics from School of Materials Science and Engineering, Beihang University. He is currently working as an assistant researcher at Kunming University of Science and Technology. He focuses on the investigations about design and preparation, thermodynamic properties and electromagnetic loss performance optimization of ultra-high temperature thermal barrier coating and high temperature stealth coating. The relevant research results have been applied to many types of engines. Currently, he has published more than 30 papers in peer-reviewed international journals including J Adv Ceram, APL, J Eur Ceram Soc, J Am Ceram Soc, JMR&T, Ceram Int, with citations ca 1000 times with H-index of 20. More than 10 national invention patents were authorized. He presides over the National Natural Science Foundation youth project, participates in the two aircraft special project, 173 National defense basic research and the military Commission Science and Technology Commission innovation Special zone and other projects.
About Journal of Advanced Ceramics
Journal of Advanced Ceramics (JAC) is an international academic journal that presents the state-of-the-art results of theoretical and experimental studies on the processing, structure, and properties of advanced ceramics and ceramic-based composites. JAC is Fully Open Access, monthly published by Tsinghua University Press, and exclusively available via SciOpen. JAC's 2023 IF is 18.6, ranking in Top 1 (1/31, Q1) among all journals in "Materials Science, Ceramics" category, and its 2023 CiteScore is 21.0 (top 5%) in Scopus database. ResearchGate homepage: https://www.researchgate.net/journal/Journal-of-Advanced-Ceramics-2227-8508
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