FeCo/ZnO composites with enhancing microwave absorbing properties: effect of hydrothermal temperature and time

FeCo/ZnO composites were successfully synthesized by a simple one-step hydrothermal process. It is clearly seen that the pencil-like ZnO particles with 3-4 mu m in length and 200-300 nm in width are found to grow along the surface of the hexagonal-cone FeCo particles, which form a discontinuous conductive network. Enhanced microwave absorption properties can be obtained for the FeCo/ZnO composites as compared to those of pure FeCo alloy, which is mainly attributed to the better resonance according to an isotropic antenna mechanism. Further investigation confirms that the hydrothermal temperature (T) and time (t) play a key role on the real part of the permittivity values of the FeCo/ZnO composites and indirectly affect the microwave absorbing properties. It is surprising to find out that the composite prepared at 150 degrees C for 12 hours, exhibited the optimal reflection loss of -31 dB with a 5.5 GHz effective frequency bandwidth.