In-situ construction of carbon fiber gradient periodic structure in Al2 O3f /SiOC composites for ultra-broadband and high-temperature electromagnetic wave absorption

Ceramic matrix composites (CMC) are widely utilized in high-temperature components of aero-engines for load-bearing and electromagnetic stealth synergy due to their superior toughening and designable electromagnetic properties. However, the design of ultra-broadband electromagnetic wave (EMW) absorption at thin thicknesses ( < 10 mm) has been difficult and focused, especially the design of metamaterial. Inspired by 3D printing technology and the structural characteristic of 2D CMC, this study ingeniously devised and proposed a novel carbon fiber gradient periodic structure in AlO/SiOC composites to enhance the ultra-broadband EMW absorption properties at a wide temperature range. By optimizing the geometric structure parameters, the AlO/SiOC composites with the carbon fiber gradient periodic structure have exhibited exceptional ultra-broadband EMW absorption properties at elevated temperatures and excellent mechanical performance. The composites have attained a minimum reflection loss (RL) of -30 dB and a high absorption efficiency of more than 84 %, ranging from 9.3 to 40 GHz at a thickness of 9 mm. Due to the temperature insensitivity of discrete periodic structures, the composites can adapt to high temperatures up to 700 degrees C. Additionally, compared to the AlO/SiOC composites, the flexural strength and fracture toughness of the AlO/SiOC composites with carbon fiber gradient periodic structure have significantly increased to 398 MPa and 15.6 MPa m, respectively. This work breaks through the limitation of the design and fabrication of 3D periodic structures in CMC, creating a novel oxide-CMC with ultra-broadband EMW absorption properties at a wide temperature range and enhanced mechanical properties.