Synthesis and microwave absorption enhancement of NiO nanosheets@SiO ₂@graphene hierarchical structures

Three kinds of NiO@SiO₂@graphene hierarchical structures, NiO nanoparticles@SiO₂@graphene, NiO nanosheets@SiO₂@graphene and NiO nanoflowers@SiO₂@graphene composites were successfully fabricated by multi-step routes. The measured electromagnetic parameters show that NiO nanosheets@SiO₂@graphene composites exhibit enhanced microwave absorption performance with wide absorption bandwidth as compared to NiO nanoparticles@SiO₂@graphene and NiO nanoflowers@SiO ₂@graphene. The maximum reflection loss can reach -43.8 dB at 11.6 GHz with a thickness of 3 mm, and the absorption bandwidth with the reflection loss below -10 dB is 5.8 GHz (from 9.2 to 15 GHz). In addition, the mechanisms for the enhanced absorption performance are also discussed.