Hierarchically Porous Multiphase Si‐Based Ceramics with Synergistic Electromagnetic Wave Absorption Mechanisms

The development of high-performance electromagnetic wave absorbers is critical for mitigating electromagnetic pollution in modern electronic and communication systems. Here, a scalable strategy is developed to fabricate hierarchically porous, multiphase Si-based ceramics (Si_x-O_y-C_z) via one-step activation of carbon-rich polycarbosilane precursors. The resulting material integrates β-SiC crystals, amorphous SiOC, and conductive carbon within a tunable porous architecture. This combination creates abundant heterogeneous interfaces, defect structures, and enhanced impedance matching. The optimized sample achieves a minimum reflection loss of -70.44 dB at just 1.79 mm thickness and a broad 4.32 GHz bandwidth at a matching thickness of 1.86 mm. Structural, dielectric, and radar simulation analyses reveal that interfacial polarization, dipolar polarization, conduction loss, and pore-induced scattering work synergistically to dissipate electromagnetic energy. This work offers a simple, cost-effective approach to engineer next-generation ceramic EMW absorbers.