Preparation and microwave absorption properties of Gd-Co ferrite@silica@carbon multilayer core-shell structure composites

Developing microwave absorbing materials having a low reflection loss (RL) and wide effective absorption band (EAB) is important. In this study, spherical Gd-Co ferrite nanoparticles were synthesized by using a co-precipitation method. Silica and carbon shells were coated on the surface of Gd-Co ferrite particles by poly-merizing tetraethyl orthosilicate and glucose. Three composites were prepared: Gd-Co ferrite@silica, Gd-Co ferrite@carbon, and Gd-Co ferrite@silica@carbon. The results showed that Gd-Co ferrite@silica@carbon exhibited the best absorbing performance, with its RL reaching the minimum value of -46.85 dB and its EAB was 3.14 GHz (8.74-11.88 GHz) at an absorption layer thickness of 2.5 mm and a frequency of 9.93 GHz. This excellent microwave absorption performance is attributed to two factors: the magnetic loss caused by the natural resonance and eddy current loss of Gd-Co ferrite and the dielectric loss enhanced by the interfacial polarization and dipole polarization caused by the multilayer core-shell structure such that the composite has excellent impedance matching. Thus, Gd-Co ferrite@silica@carbon composites can be used as high-performance micro-wave absorption material.