Synthesis of double-shell carbonyl iron powder @SiO2 @C for enhanced electromagnetic wave absorption

Enhancing the electromagnetic wave absorption bandwidth and reflection loss depth of carbonyl iron powder (CIP) is a known challenge. Building a core-shell structure for electromagnetic wave absorbing materials is one of the most effective methods available. In this paper, tetraethyl orthosilicate was used as the SiO2 source and glucose-coated as the carbon source, and then the capsules were carbonized at 300 degrees C for 5 h to obtain CIP@SiO2 @C capsules with a bilayer shell structure. The minimum RL was - 62.2 dB at 11.9 GHz with a thickness of 1.73 mm, and the effective absorption bandwidth (RL < -10 dB) was up to 8.6 GHz at 1.64 mm coating thickness, covering almost the whole X and Ku bands(8-18 GHz). The results showed that the microwave absorption performance significantly improved after introducing SiO2 and carbon shell layer structure. The excellent absorption performance can be attributed to the enhanced eddy current loss., impedance matching characteristics, and the synergistic effect of dielectric and magnetic losses after the introduction of the coating. We believed that this work would provide a valuable reference for structural design and optimization of high-performance absorbing materials.