Microwave absorbing property and preparation of CoNi@SiO₂@PPy composite in X-band

CoNi alloy@SiO₂@Polypyrrole microwave absorbing nanocomposites with three-layer core–shell structure was synthesized successfully through three-step reaction: Co20Ni80 core preparation via a solvothermal reaction, SiO₂ coating by a modified stöber method and Polypyrrole (PPy) coating through an in-situ polymerization. The surface morphologies and chemical components were characterized by field emission scanning electron microscope, X-ray diffraction and X-ray photoelectron spectroscope. The results indicate that the SiO₂ and PPy shells coat CoNi core successfully and completely. the saturation magnetization (Ms) of CoNi@SiO₂@PPy nanocomposites are 42.1 emu/g. the effective complementarity between magnetic loss contributed by CoNi cores and dielectric loss from SiO₂ and PPy shells makes CoNi@SiO₂@PPy significant enhanced microwave absorbing capacity. The minimum reflection loss could up to − 34.19 dB at frequency of 9.59 GHz with a very thin thickness 2.12 mm, furthermore, in this thickness, the effective absorbing bandwidth with reflection loss less than − 10 dB is the entire X-band, showing that the CoNi@SiO₂@PPy nanocomposites a very outstanding and promising microwave absorber.