High-performance microwave absorption epoxy composites filled with hollow nickel nanoparticles modified graphene via chemical etching method

High efficient microwave absorption materials are in emergent demand for civil and military application, especially these with light weight and broad absorption bandwidth. In this work, lightweight microwave absorbers consisting of hollow nickel nanoparticles modified reduced graphene oxide (GHN) and epoxy matrix have been successfully prepared via chemical etching method and solution blending process. SEM and TEM images showed that hollow Ni nanospheres are uniformly anchored on the surface of graphene sheets. The introduction of magnetic Ni nanoparticles into dielectric graphene improved integral properties, not only reducing the density but also enhancing microwave absorption capacity. Compared with single hollow Ni samples or graphene samples, GHN/epoxy samples exhibited extraordinary performance originating from the specific structure and multiple loss mechanism. A delta-function and microwave attenuation constant were adopted to quantitatively evaluating the impedance matching condition and microwave energy consumption ability. For GHN-10 samples, optimal reflection loss (RL) could reach up to -33.1 dB with a matching thickness of 4.9 mm. As the coating thickness decreased to 2 mm, the corresponding RI. still remained an acceptable numerical value of -23.8 dB and the effective absorption bandwidth extended to about 6.5 GHz (11.5-18 GHz), covering the whole Ku band. The as-synthesized high-performance microwave absorbers would pave a new and promising way to obtain lightweight, broad-band and strong microwave absorption materials.