Flower-like Co@CoO nanohybrids assembled by crisp-rice-like quadrate flakes as high-performance electromagnetic wave absorber

Microstructure design has gradually emerged as an effective strategy for achieving high electromagnetic wave absorption. Here 3D flower-like Co@CoO nanohybrids composed of crisp-rice-like core-shell Co@CoO quadrate flakes are crafted utilizing a simple hydrothermal-thermal reduction strategy. The as-prepared quadrate flake-assembled architectures could facilitate the electron migrating/hopping and the formation of conductive network, leading to the conductive loss augment. The experimental results show that the contribution factor of the conductive loss could be tuned through adjusting the loading of Co@CoO nanohybrids. Meanwhile, the abundant surface, Co-CoO interfaces and active sites (e.g., defects, dangling bonds, and functional groups) boost the interfacial polarization and dipole polarization of Co@CoO nanohybrids. Moreover, the affluent cavities as well as certain-angle-arranged flakes also empower the multiple reflection/scattering of electromagnetic wave. Due to the combination of the multiple absorption mechanisms including conductive loss, dipole polarization, interfacial polarization, natural resonance, eddy current loss and multiple scattering, flower-like Co@CoO achieves good EM wave absorption performance. 35 wt% flower-like Co@CoO/paraffin composite exhibits a high RL value of −44.76 dB (f = 9.19 GHz, d = 1.91 mm), and 40 wt% flower-like Co@CoO/paraffin composite presents wide effective bandwidth (RL < −10 dB) of 3.75 GHz with a thickness of only 1.51 mm.