Design of hollow ZnFe2O4 microspheres@graphene decorated with TiO2 nanosheets as a high-performance low frequency absorber

The ternary composite of hollow ZnFe2O4 microspheres@graphene decorated with TiO2 nanosheets was fabricated by two-step hydrothermal method. FESEM and TEM images illustrate that hollow ZnFe2O4 microspheres with an average diameter of about 300-500 nm were attached to the surface of transparent graphene sheets. In addition, TiO2 nanosheets were grown on the top of ZnFe2O4@graphene with a random orientation. Electromagnetic (EM) wave absorption results demonstrate that the maximum reflection loss (RL) of ZnFe2O4@graphene@TiO2 composite are significantly enhanced, which can be up to −55.6 dB at 3.8 GHz for a coating of 2.5 mm. The maximum absorbing bandwidth exceeding −10 dB is almost 6.4 GHz (2.8-5.4 GHz, 12.9-14.5 GHz, 15.8-18 GHz) at only 2.5 mm. Consequently, it is supposed that the hierarchical structure of ZnFe2O4@graphene@TiO2 composite can be served as a promising microwave absorber, especially in low frequency.