Rapid Microwave Plasma Engineering of HfO₂/C@C Core-Shell Fibrous Membrane Toward Flexible High-Performance Electromagnetic Wave Absorption

Flexible electromagnetic wave (EMW) absorbers that simultaneously exhibit excellent impedance matching, strong attenuation capability, and mechanical robustness remain highly desirable yet challenging to realize, particularly for dielectric HfO₂-based materials owing to their intrinsically low conductivity and limited polarization capability. Herein, a rapid and environmentally friendly CO₂ microwave plasma torch strategy is developed to fabricate flexible HfO₂/C@C core-shell fibrous membranes with tunable defects. The ultrafast plasma process simultaneously regulates the crystalline structure of HfO₂, the graphitization of the carbon shell, and the concentration of oxygen vacancies, thereby constructing highly coupled dielectric-conductive heterointerfaces. Therefore, the optimized HfO₂/C@C-2 sample exhibits outstanding microwave absorption, with a minimum reflection loss of −65.75 dB at 3.2 mm and an effective absorption bandwidth of 7.37 GHz. Meanwhile, the interconnected one-dimensional fibrous network endows the material with excellent flexibility and fatigue resistance, while radar cross-section simulations further demonstrate its superior stealth capability. This work establishes a clear processing-structure-property relationship and proposes a green plasma strategy to overcome the performance-practicality trade-off of HfO₂-based absorbers, providing a promising route toward next-generation flexible EMW absorbing materials.