Designing Co7Fe3@TiO2 Core–Shell Nanospheres for Electromagnetic Wave Absorption in S and C Bands

Abstract

Ferromagnetic-dielectric nanocomposites have attracted extensive interests for its high electromagnetic wave absorption (EMA) performance due to the synergetic effects between different components. Herein, we report the design of core–shell structured Co7Fe3@TiO2 composite particles, which are subsequently annealed in H2/Ar atmosphere to further improve its EMA performance. The introducing of TiO2 dielectric shell together with hydrogen annealing contributes greatly to the electromagnetic properties due to the increased conductivity and enhanced ferromagnetic resonance. Excellent EMA performance is achieved in S (2–4 GHz) and C (4–8 GHz) bands in coatings using Co7Fe3@TiO2 as absorbents. Apart from the high EMA efficiency, the location of EMA band can be tailored in a wide range through regulating the coating thickness. Specifically, an effective absorption band of 2.0 GHz in C band at a thickness of 2.62 mm, and an effective absorption band of 1.7 GHz are achieved in S band at thicknesses of 4.0–5.0 mm. The excellent electromagnetic properties are ascribed to the effective complementary between dielectric loss and ferromagnetic loss.