Direct Growth of Edge-Rich Graphene with Tunable Dielectric Properties in Porous Si₃N₄ Ceramic for Broadband High-Performance Microwave Absorption

High-performance graphene microwave absorption materials are highly desirable in daily life and some extreme situations. A simple technique for the direct growth of graphene as absorption fillers in wave-transmitting matrices is of paramount importance to bring it to real-world application. Herein, a simple chemical vapor deposition (CVD) route for the direct growth of edge-rich graphene (ERG) with tailored structures and tunable dielectric properties in porous Si₃N₄ ceramics using only methyl alcohol (CH₃OH) as precursor is reported. The large O/C atomic ratio of CH₃OH helps to build a mild oxidizing atmosphere and leads to a unique structure featuring open graphite nanosteps and freestanding nanoplanes, endowing the ERG/Si₃N₄ hybrid with an appropriate balance between good impedance matching and strong loss capacity. Accordingly, the prepared materials exhibit superior electromagnetic wave absorption, far surpassing that of traditional CVD graphene and reduced graphene oxide-based materials, achieving an effective absorption bandwidth of 4.2 GHz covering the entire X band, with a thickness of 3.75 mm and a negligibly low loading content of absorbents. The results provide new insights for developing novel microwave absorption materials with strong reflection loss and wide absorption frequency range.