Preparation of nanocrystalline-coated carbon nanotube/Ni0.5Zn0.5Fe2O4 composite with excellent electromagnetic property as microwave absorber

A combined precipitation-hydrothermal method was used to fabricate carbon nanotube/Ni0.5Zn0.5Fe2O4 ferrite composite powders. The phase, microstructure and electromagnetic properties of CNT/NiNi0.5Zn0.5Fe2O4 composites were investigated. After surface modification, The zeta potential value of CNTs could maintain at about -50mV when pH is higher than 8, which affords a suitable surface environment for in situ coating of NiNi0.5Zn0.5Fe2O4 nanocrystallines. With increasing CNTs content, the saturation magnetization of the composites is gradually reduced, while the complex magnetic permeability changes little. The complex dielectric constant of the composites is significantly increased when the concentration of CNTs approaches the percolation threshold value of 2 wt%. When CNTs content is 5 wt%, the reflection ratios are less than -10 dB within the frequency range 2-9 GHz, and the reflection ratios reach a minimum -32.5 dB at a frequency of about 3.9 GHz.