Multifunctional Metamaterial Microwave Blackbody with High-Frequency Compatibility, Temperature Insensitivity, and Structural Scalability

Compared with optical black, few attempts have focused on achieving broadband microwave blackbodies. In this study, all-ceramic metamaterial microwave blackbodies are created by integrating a graded Gyroid shellular (GGS) metastructure design with additive manufacturing of polymer-derived SiOC (PDCs-SiOC) ceramics encapsulated by Si₃N₄ (SiOC@Si₃N₄). Hardly influenced by the destructive interference effect, as-fabricated GGS-structured SiOC@Si₃N₄ microwave blackbodies demonstrate a broadband microwave absorption (MA) above 83.6% (91.3% on average) across the entire X-Ku band and encompassing higher frequencies above 18 GHz as well, together with the temperature insensitivity from room temperature to 500 °C. Based on the flexible electromagnetic tunability of PDCs-SiOC, exceptional structural scalability is experimentally validated for metal-doped modified CuSiOC and CoSiOC substrates with the same GGS metastructures, retaining high-efficiency MA capability. Furthermore, attachment of perfectly reflecting metal backplanes further enhances the MA performance, with an ultrawide MA exceeding 67.9% (89.1% on average) achievable at 2.95–18 GHz for CoSiOC substrate. Meanwhile, the GGS-structured SiOC@Si₃N₄ metamaterials possess additional multifunctional properties, such as good noise reduction performance as well as ultrahigh wear resistance. As a proof of concept, this study provides important guidance on achieving multifunctional coupling broadband MA characteristics by fully tapping the application potential of existing materials.