General Biotemplating of Hierarchically Ultra-Vesicular Microspheres for Superior Microwave Absorption

The vesicular structure has elicited increasing interest in the field of lightweight microwave absorption (MA) materials. However, few methods exist to integrate both microand nanoscale vesicles within one nano architecture. Herein, the high-yield and green biotemplate method is developed for the general synthesis of hierarchically ultra-vesicular microspheres (HUVMs), consisting of a hollow configuration and numerous multi sized bubbles inside. HUVMs of metal oxides (SnO2, Co3O4, Fe2O3, and Mn2O3), their combinations, and magnetic metals (Co and CoNi) have been successfully prepared. Their synergistic multi-sized vesicles simultaneously enhance dielectric loss capacity by space charge polarization and satisfy impedance matching by large cavities, proved by electron holography. Eventually, both the SnO2 and Co HUVMs demonstrate first-rank MA performance covering almost the whole bandwidth from 2 to 18 GHz with ultrahigh absorption intensity beyond -40.0 dB. These achievements provide a new avenue for precise manipulation of ultra-porous structure and foreshadow an important direction of lightweight absorbents.