Hierarchical CNTs/PyC/SiBCN foam with tunable microwave absorption properties conspired by melamine-derived pyrolyzed carbon and carbon nanotubes

Three-dimensional (3D) porous carbon-based materials have garnered significant attention for their potential applications for electromagnetic wave absorption. In this study, a novel 3D porous foam composed of pyrolytic carbon (PyC), carbon nanotubes (CNTs), and silicoboron carbonitride (SiBCN) ceramics was proposed with a three-layer coating structure. The hierarchical CNTs/PyC/SiBCN foam was synthesized through a combination of melamine foam pyrolysis, CNTs impregnation, and polymer-derived ceramics technology. By synergistically adjusting the CNTs content and pyrolysis temperature, the dielectric properties of the foam were effectively tailored, enabling efficient regulation of electromagnetic wave absorption performances in 8.2–12.4 GHz (X Band). Experimental results demonstrate the foam's effectiveness in absorbing electromagnetic wave in the whole X band, with a minimum reflection loss of −47.5 dB at a thickness of 4.4 mm, with the CNTs content of 0.3 % and the pyrolysis temperature of 800 °C. The electromagnetic wave absorption mechanism of the composites is clarified from multiple electromagnetic wave loss modes caused by heterogeneous structures, providing new insights for developing lightweight and efficient microwave absorbing materials.