Superior Microwave Absorption Performance of Hierarchical Coni Chains than Particles

CoNi alloys are excellent magnetic microwave absorption materials, and the influence of various structures on performance is very significant, especially chains versus particles. Herein, a magnetic field-induced solvothermal method was applied to prepare hierarchical CoNi chains, and without the magnetic field, corresponding CoNi particles were obtained. Tailoring the reaction time can change the hierarchical surface structures of samples, which are observed through SEM images. XRD results reveal the crystalline structures, lattice constants, mean crystallite sizes, and internal stresses of samples. Magnetic properties and microwave absorption performance have been investigated. CoNi chains possess stronger saturation magnetization and higher coercivity than CoNi particles due to their larger crystalline sizes and higher aspect ratios. Moreover, CoNi chains exhibit superior microwave absorption capacity than CoNi particles, and the minimum reflection loss value can reach -42.113 dB (16.5 GHz) together with an effective absorption bandwidth of 3.5 GHz (13-16.5 GHz). Possible microwave absorption mechanisms of CoNi chains involve conductive loss from antenna effect of chain-like structure, abundant interfacial polarizations from hierarchical porous surface, more eddy current effect and exchange resonance. This work first reveals the reason that CoNi chains are more promising candidates than particles in the application of microwave absorption