Mesoporous core-shell structure NiFe_2O_4@polypyrrole micro-rod with efficient electromagnetic wave absorption in C, X, Ku wavebands

摘要

Reasonable design of micro-structure and chemical constitution is an effective way to fabricate highly efficient electromagnetic (EM) wave absorbers. In this work, a series of mesoporous core-shell structure NiFe_2O_4@ polypyrrole (NFO@PPy) micro-rod composites are successfully synthesized through a convenient in-situ polymerization progress. The characterizations confirm porous one-dimensional rod-like NiFe_2O_4 (NFO) is formed by the aggregation of many nanoparticles. The amount of pyrrole (Py) greatly affects the thickness of polypyrrole (PPy) shell, as well as the relative content of magnetic and carbon components, which regulates dielectric loss and magnetic loss of NFO@PPy. To be specific, when the dosage of Py is 10% (NFO@PPy-10%), the sample manifests the best performance with the minimum reflection loss (RL_(min)) of -54.6 dB at C band (7.0 GHz). Notably, the effective absorption band (EAB, RL < -10 dB) is up to 13.7 GHz via manipulating the coating thickness which covers all C, X, and Ku wavebands. This work highlights the importance of synergistic coupling effects between dielectric loss (strong interfacial/dipolar polarizations, conductive loss, multiple scatterings) and magnetic loss (eddy current loss, natural ferromagnetic resonance, and exchange resonance) for the NFO@PPy to achieve sufficient attenuation capacity and impedance matching.