Microwave absorption properties of γ-Fe2O3/(SiO2) x –SO3H/polypyrrole core/shell/shell microspheres

Highly regulated γ-Fe2O3/(SiO2) x –SO3H/polypyrrole (FS x HP) composite core/shell/shell microspheres are successfully prepared through a SiO2 sol–gel process and an in situ polymerization of pyrrole monomers. γ-Fe2O3 functions as the “core,” whereas SiO2 and polypyrrole (PPy) act as the “shells” of the composite. In contrast to many previously reported FS2H-P and PPy-based composites, the FS x HP composites display substantially improved microwave absorption properties, which can reach nearly − 43.1 dB (15.1 GHz) with a broader effective absorption bandwidth (RL < − 10 dB) of 6.1 GHz. The excellent microwave-absorbing properties of the FS x HP composites are closely associated with the layer of SiO2 shells and can be attributed to the proper impedance matching and synergistic interaction of the special core/shell/shell structures, dielectric loss (SiO2 and PPy layers) and magnetic loss (γ-Fe2O3). These results show that the core/shell/shell structure may be an efficient and promising way to improve microwave absorption properties.