Magnetic-dielectric synergistic coral-like CoNi@SiO2 microparticles for high-efficiency and broadband microwave absorption

Magnetic-dielectric functional materials with unique three-dimensional (3D) anisotropic structures, reasonable component regulation, and hierarchical heterogeneous interfaces are potential candidates for achieving efficient microwave absorption (MA). In this paper, CoNi/SiO2 hybrids are synthesized for high-performance MA by anchoring the dielectric SiO2 layer by Sto<spacing diaeresis>ber's sol-gel method to regulate the permittivity (epsilon r). The results show that the abundant pores and high specific surface area of the coral-like spherical structure, the epsilon r modulation of CoNi alloy by SiO2 shell-layer, the heterogeneous interface and charge storage capacity difference between both, which provide more reflective and scattering channels for the incident electromagnetic wave (EMW), optimize the impedance matching and enhance the interfacial polarization loss and magnetic loss, and finally achieve the reflection loss (RL) enhancement and effective absorption bandwidth (EAB) broadening. In particular, the corallike CoNi@SiO2-2 microparticle (MP) has the strongest RL of -66.59 dB at 2.2 mm matching thickness and the maximum EAB of 6.460 GHz at 1.9 mm matching thickness, which covers the entire Ku-band. In this study, the hierarchical heterostructure is constructed by a unique morphology design and the introduction of a dielectric anchoring layer, which provides a new way to prepare efficient microwave-absorbing materials by magneticdielectric coupling engineering.