3D graphene-Ni microspheres with excellent microwave absorption and corrosion resistance properties

In this study, we report a simple and efficient two-step method consisting of water-in-oil (W/O) emulsion technique and subsequent annealing process for synthesizing the hollow reduced graphene oxide microspheres embedded with Ni nanoparticles (Air@rGOa,notsignNi). The microspheres showed good electromagnetic properties because of the coexistence of magnetic loss and dielectric loss to microwaves. The minimum reflection loss (RLmin) value of Air@rGOa,notsignNi microsphere reaches up to - 59.7 dB at 11.6 GHz with a thickness of 2.7 mm and an absorption bandwidth (lower than - 10 dB) is 4.8 GHz (9.4-14.2 GHz). Their resistance to chemical corrosion is amazingly, after treatment in hydrochloric acid for 5 days, the saturation magnetization (Ms) values of Air@rGOa,notsignNi microsphere has fallen only six percentage points. More interestingly, we can easily controll the microwave absorbing properties of the microspheres by changing the ratio of the two components in the composites. The unique 3D structure and excellent electromagnetic match at the corresponding resonance peaks for dielectric and magnetic loss play an important role in improving microwave absorption property. Our study provides a good potential method for preparation of lightweight microwave absorbing materials.