“…For example, porous Si 3 N 4 ceramic with low permittivity has been employed in missile radome due to their good electromagnetic waves transparency [2]. And the Si 3 N 4 ceramic composites containing pyrolytic carbon [4] or carbon fiber [5], exhibit excellent electromagnetic absorbing properties because of the good matching between permittivity and permeability. Oppositely, if permittivity and permeability of material aren't comparable, electromagnetic waves will be reflected back at the material surface, which is the primary mechanism of electromagnetic shielding [1,6].…”
“…Moreover, pyrolytic carbon-Si 3 N 4 ceramic composites with gradient PyC distribution (Gradient-PyC-Si 3 N 4 ) were prepared by directional oxidation PyC-Si 3 N 4 in the air with the help of Si 3 N 4 coating. After oxidation for 1.0 h, the EMW absorption ability of the Gradient-PyC-Si 3 N 4 increased from 0.8 to 50.1% [279]. Figure 17. Schematic illustration of a multilayered EMW materials structure.…”
Section: Emw Absorbing Performance Based On Microstructural Designmentioning
Electromagnetic wave (EMW) absorbing materials have attracted much attention in recent years due to the dramatical increase of high-frequency electronic components and devices, which generate electromagnetic (EM) pollution and cause serious electromagnetic interference (EMI). Ceramics and associated (nano)composites are widely investigated as EMW absorbing materials because of their excellent mechanical properties, chemical/ thermal stabilities, and oxidation/corrosion resistance. In addition to outstanding EMW absorbing performance, lightweight, flexibility and thermal resistance at high temperatures strongly affect their practical applications. Therefore, this review highlights the recent progress of advanced ceramic-based EMW absorbing materials by evaluating their vital EMW absorption parameters. First, the fundamentals of EMW absorption are briefly summarized, followed by the effects of phase/chemical composition, micro/nano structure, and morphology on the EMW absorbing performance and associated mechanisms. Furthermore, modern strategies for the preparation of lightweight, flexible and thermal resistant EMW absorbing materials are comprehensively reviewed. Finally, the perspectives of advancedceramics as EMW absorbing materials are discussed as well.
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