Carbon-encapsulated core-shell structure ZnFe₂O₄ sphere composites coupled with excellent microwave absorption and corrosion resistance

Microwave absorbing materials (MAMs) have been identified as an efficient means to solve major electromagnetic pollution problems. Current core-shell composite MAMs are fabricated as single magnetic cores with dielectric shells, yielding decreased magnetic couplings and impedance mismatches. Herein, carbon shell encapsulated core-shell structured zinc ferrate (ZnFe₂O₄) sphere composites (CSZF@C) were fabricated using a hydrothermal method and subsequent carbonisation process. The complex permittivity and complex permeability of CSZF@C can be effectively adjusted by varying the parameters of the outer carbon shell. The synergistic effect of carbon shell and inner core-shell structured ZnFe₂O₄ (CSZF) not only meets impedance matching but also improves electromagnetic energy loss, a result of the unique microstructure. CSZF@C-1 exhibited a considerable reflection loss (RL) of −53.5 dB and an effective absorption bandwidth (EAB) of up to 6.56 GHz, the thickness is only 2.94 mm. Meanwhile, the epoxy resin coating of CSZF@C-1 substantially increases the corrosion resistance of the metal substrate owing to carbon encapsulation. This study presents new ideas for designing efficient multifunctional nanocomposites with high microwave absorption and corrosion resistance.