Simple Salt-Template Assembly for Layered Heterostructures of C/Ferrite and EG/C/MFe2O4(M = Fe, Co, Ni, Zn) Nanoparticle Arrays toward Superior Microwave Absorption Capabilities

Layered C/ferrite nanoparticle array (NPA) and expanded graphite (EG)/C/MFe2O4(M = Fe, Co, Ni, Zn) NPA heterostructures are synthesized via a simple sodium salt-template method. An array of well-distributed ferrite nanoparticles supported by layered carbon grows simultaneously on the EG surface from metal-oleate complexes. Some dynamic factors are systematically optimized to well adjust the size, content, and morphology of the heterostructures. The heterostructures show good soft magnetic nature with theM(s)decreasing in the following order: EG/C/gamma-Fe2O3 > EG/C/CoFe2O4 > EG/C/NiFe2O4 > EG/C/ZnFe2O4. As microwave absorbers, these heterostructures of EG/C/MFe(2)O(4)NPA exhibit significantly enhanced electromagnetic-wave absorbing capabilities (EWACs) compared with pure EG, EG/gamma-Fe(2)O(3)NPA heterostructure, and other C-based composites. Hereinto, EG/C/CoFe(2)O(4)NPA heterostructures exhibit the optimal EWAC with a minimal reflection loss of -49.85 dB at 13.9 GHz and a 1.3 mm coating thickness. The frequency range of 99% absorption is over 2.0-17.0 GHz and the corresponding thickness is 1.10-8.0 mm. The excellent microwave absorption relies on cooperation of double dielectric relaxations, natural resonance, eddy current loss, high attenuation, and appropriate impedance matching. Therefore, layered heterostructures of EG/C/MFe(2)O(4)NPA are promising electromagnetic wave absorbers for practical application.