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

Abstract

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 polymerizing 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 microwave absorption material.