Interconnected magnetic carbon@NixCo1-xFe2O4 nanospheres with core–shell structure: An efficient and thin electromagnetic wave absorber

The applications of cobalt ferrite and nickel ferrite composite materials on electromagnetic (EM) wave absorption are the research hotspot currently. However, the systematical comparison study between these two ferrites composites have rarely been carried out. Thus, the EM wave absorption performance of interconnected carbon@Ni x Co 1-x Fe 2 O 4 composites with core–shell structures were investigated comprehensively in this work. A series of magnetic nanospheres including NiFe 2 O 4 , cobalt-doped nickel ferrite, nickel–cobalt ferrite, nickel-doped cobalt ferrite and CoFe 2 O 4 were synthesized firstly, and then uniformly encapsulation by carbon rendered the corresponding C@Ni x Co 1-x Fe 2 O 4 composites nanospheres. Synthesis reactions involved for C@Ni x Co 1-x Fe 2 O 4 formation were investigated in detail, and afterwards their magnetic behavior, EM wave absorption performance and absorbing mechanism were thoroughly explored and analyzed. Results show that when nickel is dominant element and cobalt is doping element (Ni 0.75 Co 0.25 Fe 2 O 4 ), the composite nanosphere exhibits optimum EM wave absorption performance. When the sample thickness is just 1.9 mm, its RL min value can reach −51 dB, and the corresponding EAB width is 3.3 GHz. The synthesized C@Ni 0.75 Co 0.25 Fe 2 O 4 can be qualified as an efficient and thin electromagnetic wave absorber, which is mainly attributed to its special structure, fair electromagnetic matching and impedance matching.