Electromagnetic Wave Absorption Properties of Coatings with Carbonyl-iron Particles coated by Silicon dioxide Nano-powders
Silicon dioxide nano-powders prepared by gas-phase synthesis method were directly added into the solvent. The carbonyl iron particles (CIP) were partially coated by a thin layer of silicon dioxide in the solvent. Such coated particles were used as absorbent, with Aliphatic Polyurethane (APT) resin as matrix, to prepare the microwave absorbing coating. The morphology, elemental composition and electromagnetic characteristics of silicon dioxide coated and uncoated CIP were studied using SEM, EDS, and a voter network analyzer. Its electromagnetic parameters were measured in the range from 2GHz to 18GHz. The results show that the direct mixing method can effectively change the iron-based particle electromagnetic parameters, achieving the purpose of regulating the impedance matching. The minimum reflection loss of the coating shifts to the high-frequency region with increasing weight concentrations of silicon dioxide. The peak value of -31.1 dB was obtained at 16.5 GHz for the coatings with 50 wt.% CIP and 5wt.% silicon dioxide nano-powders.