Coral‐Like Yolk–Shell‐Structured CoNi@Void@C Microspheres for Enhanced Microwave Absorption, Photothermal, Anti‐Corrosion, and Radiation Shielding Properties

ABSTRACT Considering the multiple challenges faced by stealth coatings in complex service environments, the development of multifunctional integrated microwave absorbing materials (MAMs) that combine efficient electromagnetic (EM) attenuation with environmental tolerance has become an urgent need. In this work, coral‐like CoNi@Void@C microparticle (MP) with the yolk–shell structure was synthesized through a continuous process combining conventional solvothermal, sol‐gel, oxidative self‐polymerization, and acid etching. The precise construction of the magnetic core–cavity–carbon shell structure synergistically optimizes impedance matching and multiple loss mechanisms, endowing the material with outstanding microwave dissipation performance. A minimum reflection loss (RL min ) of −81.24 dB and an effective absorption bandwidth (EAB) of 6.21 GHz are achieved at an ultra‐thin matching thickness ( d m ), and the excellent EM stealth capability is confirmed by a radar cross‐section value of 51.82 dB m 2 . Additionally, the barrier effect of the cavity buffer layer and nonpolar carbon shell simultaneously endow it with low density, super‐hydrophobicity, efficient photothermal conversion, corrosion resistance, and performance reinforcement for ionizing radiation shielding, demonstrating potential adaptability in various environments. This work provides a new paradigm for the next generation of environmentally adaptive MAMs through a three‐level synergistic strategy of “morphology–cavity–interface”.