Fabrication of hollow microhemisphere-like polypyrrole and carbon dielectric materials by sol–gel template method for enhanced microwave absorption

Abstract

Hollow-microstructured dielectric materials offer immense potential for next-generation lightweight high-performance microwave absorbers with strong reflection loss and wide absorption frequency bandwidth. Herein, we demonstrate the successful synthesis of hollow polypyrrole microhemispheres (HPMs) and hollow carbon microhemispheres (HCMs) via a facile sol–gel method with SiO2 microspheres as the templates. Compared to some of polypyrrole and carbon absorbers reported previously, HPMs and HCMs exhibit excellent microwave absorption performances. Particularly, HCMs possess stronger conductive loss and better characteristic impedance matching than HPMs, displaying superior microwave absorption properties. Combining with disordered and aggregated nanoparticles as control samples, their electromagnetic analysis further reveals that the improved dielectric loss, optimized impedance matching, and multiple reflection/scattering derived from hollow hemispherical microstructures primarily account for the enhanced microwave absorption performance of these hollow microhemisphere-like products. It is believed that this work provides a new idea for preparing high-performance dielectric microwave absorbers by construction of their hollow microstructure.