Preparation and evaluation of the microwave absorption properties of template-free graphene foam-supported Ni nanoparticles

A template-free graphene foam-supported Ni nanoparticle (GFN) composite was prepared by a hydrothermal method, followed by a calcination process. Phase, composition and morphology of the composites were characterized by XRD, Raman spectroscopy, FTIR, XPS, FESEM, and TEM. GFN exhibited a well-defined and interconnected three-dimensional (3D) network structure without template, and Ni nanoparticles were uniformly dispersed on the graphene nanosheets and attached via C-Ni covalent bonds. The microwave absorption (MA) properties of the samples were also investigated with a vector network analyzer. Based on the 3D structure of graphene foam, due to interfacial effects (graphene/Ni/wax) and the synergistic effect between graphene and Ni nanoparticles, GFN showed the most remarkable MA properties, compared with the graphene foam-supported NiO nanoparticles composite (GFNO), pure graphene foam (GF) and pure Ni nanoparticles. When the thickness of the GFN/wax sample was 3.4 mm and the content of GFN in the sample was only 1 wt%, the maximum reflection loss of GFN could reach −49 dB at 11.5 GHz. This high reflection loss was a result of the multiple reflections and attenuations of electromagnetic waves within the 3D structure of the graphene foam, the interfacial polarization and the better impedance matching characteristics of GFN. Hence, a template-free graphene foam-supported Ni nanoparticle composite with strong absorption and lightweight properties showed a promising future in microwave absorption applications.