Fabrication of cobalt-zinc bimetallic oxides@polypyrrole composites for high-performance electromagnetic wave...

Composite materials that combine magnetic and dielectric losses offer a potential solution to enhance impedance match and significantly improve microwave absorption. In this study, Co₃O₄/ZnCo₂O₄ and ZnCo₂O₄/ZnO with varying metal oxide compositions are successfully synthesized, which are achieved by modifying the ratios of Co²⁺ and Zn²⁺ ions in the CoZn bimetallic metal-organic framework (MOF) precursor, followed by a high-temperature oxidative calcination process. Subsequently, a layer of polypyrrole (PPy) is coated onto the composite surfaces, resulting in the formation of core-shell structures known as Co₃O₄/ZnCo₂O₄@PPy (CZCP) and ZnCo₂O₄/ZnO@PPy (ZCZP) composites. The proposed method allows for rapid adjustments to the metal oxide composition within the inner shell, enabling the creation of composites with varying degrees of magnetic losses. The inclusion of PPy in the outer shell serves to enhance the bonding strength of the entire composite structure while contributing to conductive and dielectric losses. In specific experimental conditions, when the loading is set at 50 wt%, the CZCP composite exhibits an effective absorption bandwidth (EAB) of 5.58 GHz (12.42 GHz-18 GHz) at a thickness of 1.53 mm. Meanwhile, the ZCZP composite demonstrates an impressive minimum reflection loss (RL_min) of -71.2 dB at 13.04 GHz, with a thickness of 1.84 mm. This study offers a synthesis strategy for designing absorbent composites that possess light weight and excellent absorptive properties, thereby contributing to the advancement of electromagnetic wave absorbing materials.