Double-shell PANS@PANI@Ag hollow microspheres and graphene dispersed in epoxy with enhanced microwave absorption

Double-shell hollow conductive poly(acrylonitrile) microspheres@polyaniline@Ag (PANS@PANI@Ag) was synthesized by a facile two-step method. Polyaniline-coated poly(acrylonitrile) microspheres (PANS@PANI) prepared by in situ polymerization exhibited a porous, corrugated and compact conductive network, making for the formation and attachment of Ag nanoparticles. Incorporating these hollow conductive spheres and reduced graphene oxide (RGO) into epoxy resin, a lightweight microwave absorber was brought out. The chemical composition, micro-structure surface morphology and electromagnetic properties were thoroughly characterized and analyzed. The calculated results showed that the optimal reflection loss (RL) was − 44.9 dB at 9.16 GHz with a constitution of 1 wt% dielectric RGO and 1 wt% conductive PANS@PANI@Ag, and the corresponding effective bandwidth was about 2 GHz. However, the microwave absorption capacity gradually reduced with the raise of PANS@PANI@Ag content, derived from the high conductivity leading to more microwave reflection. As the PANS@PANI@Ag content increased to 5 wt%, the minimum RL was − 14.7 dB and still remained an effective absorption performance with a lower density of 0.47–0.53 g/cm3. Therefore, the as-obtained composites paved a new route for lightweight and strong absorption microwave absorbers in commercial and military application.