A comparative study on the microwave absorption properties of core-single-shell, core-double-shell and yolk-shell CIP/ceramic composite microparticles

Abstract

In this work, CIP@SiO2, CIP@SiO2@ZrO2 and CIP@void@ZrO2 microspheres were fabricated as model samples of the core-single-shell, core-double-shell and yolk-shell absorbents to systematically compare the role of different coating structures for microwave absorption properties and offer a comprehensive reference to the rational structural design for microwave absorbents. Microstructures, magnetic properties, electromagnetic parameters and microwave absorption of different absorbents were studied. The electromagnetic absorption performance of the as-prepared multicomponent hierarchical microspheres was superior to the sole CIP, owing to the combination of strong magnetic loss of CIP core and excellent dielectric loss of SiO2 and ZrO2 shell. For core-double-shell CIP@SiO2@ZrO2 microspheres, the minimum RL was −20.69 dB at 17.44 GHz with a thickness of 1.7 mm and the effective absorption bandwidth can reach 6.48 GHz at the coating thickness of 2 mm. It is noted that the initial oxidation temperature of CIP increased by ∼200 ℃ owing to the presence of dense SiO2 intermediate layer. Inspiringly, the minimum RL of yolk-shell CIP@void@ZrO2 microspheres was up to −28.38 dB at the absorber thickness of 2.2 mm and the effective absorption bandwidth reach 7.44 GHz from 10.24 to 17.68 GHz at 2.1 mm thickness. The yolk-shell structure had better absorbing performance than the core-shell structure because the cavity as the intermediate layer improved impedance matching. We believed that this work would provide a valuable reference for structural design and optimization of the high-performance absorbing materials.