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

In this work, CIP@SiO 2 , CIP@SiO 2 @ZrO 2 and CIP@void@ZrO 2 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 SiO 2 and ZrO 2 shell. For core-double-shell CIP@SiO 2 @ZrO 2 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 SiO 2 intermediate layer. Inspiringly, the minimum RL of yolk-shell CIP@void@ZrO 2 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.