Impact of silica-coating on the microwave absorption properties of carbonyl iron powder

•Silica coatings were prepared on the surface of carbonyl iron powder.•Coating layers were identified by several ways.•We discussed the absorbing mechanism of coated samples.•Reflection loss was significantly improved, the width of RL exceeding −10 dB is from 8 GHz to 14 GHz.

Microwave absorption properties, especially the band width and depth of reflection loss are highlighted as key measurement in studies of microwave absorber. In order to improve the band width and depth of reflection loss of carbonyl iron powder (CIP), we prepared SiO2 layers on the surface of CIP by using tetraethyl orthosilicate (TEOS) as a SiO2 source and 3-aminopropyl triethoxysilane (APTES) as a surface modifier. SiO2 layer was formed by the hydrolysis of TEOS. The results show that after treatment the CIP is covered by a 5–10 nm coating layer. Contrast to uncoated samples, coated samples show improved absorption properties. The minimum of reflection loss is −38.8 dB at 11 GHz and the band width of reflection loss exceeding −10 dB is from 8 GHz to 14 GHz.