Hierarchical CoNi alloys toward microwave absorption application: Chain-like versus particle-like

CoNi alloys are well known as excellent magnetic microwave absorption materials, but their various structures greatly influence electromagnetic properties, especially chains versus particles. Hierarchical CoNi chains were prepared using the solvothermal method in conjunction with an external magnetic field, and hierarchical CoNi particles were obtained in the absence of the magnetic field. Changing the reaction time from 6 to 12 h can change the surface structures of hierarchical CoNi alloys, as seen in the SEM images. The lattice parameters of samples are determined by XRD results, which include crystalline structures, lattice constants, mean crystallite sizes, and internal strain. The investigation of magnetic properties indicates that CoNi chains possess a stronger saturation magnetization and higher coercivity than CoNi particles as a result of their higher aspect ratios and larger crystalline sizes. Furthermore, CoNi chains have a higher microwave absorption capacity than CoNi particles, with a minimum reflection loss value of −42.113 dB (16.5 GHz) and an effective absorption bandwidth of 3.5 GHz (13–16.5 GHz). Conductive loss, defect-induced polarization relaxation, eddy current effect, exchange resonance, N é el relaxations, multiple reflections, and scatterings all contribute to the excellent microwave absorption performance of the CoNi chains. This research establishes that a chain-like structure outperforms a particle-like structure for hierarchical CoNi alloys as microwave absorbers, and it will provide clear guidance for designing high-performance magnetic microwave absorption materials.