A facile and environmentally friendly method is proposed to prepare reduced graphene oxide–nickel (RGO–Ni) nanocomposites using γ-ray irradiation. Graphene oxide (GO) and Ni²⁺ are reduced by the electrons which originated from the gamma radiolysis of H₂O. The structure and morphology of the obtained RGO–Ni nanocomposites were analyzed using X-ray diffraction (XRD) and Raman spectroscopy. The results show that Ni nanoparticles were dispersed uniformly on the surface of the RGO nanosheets. As expected, the combination of RGO nanosheets and Ni nanoparticles improved the electromagnetic wave absorption because of the better impedance matching. RGO–Ni nanocomposites exhibited efficient electromagnetic wave absorption performance. The minimum reflection loss (RL) of RGO–Ni reached −24.8 dB, and the highest effective absorption bandwidth was up to 6.9 GHz (RL < −10 dB) with a layer thickness of 9 mm.

A low infrared emissivity coating was prepared using graphene surface-modified flaky aluminum complex powders (rGO-FAl) as fillers. The flaky aluminum powders were coated with graphene through chemical bonding. Compared with pure flaky aluminum, the Vis-NIR diffuse reflectance of rGO-FAl complex powders was significantly decreased, which was beneficial to the low glossiness of the coating. After the modification, the glossiness at 60° of the coating with 40% (mass fraction) pigments decreased from 12.8 to 6.7, while the coating maintained low infrared emissivity (0.238~0.247) at a spectral range of 8–14 μm. In the electrochemical impedance spectroscopy (EIS) measurement, at the lowest frequency, the impedance of the Al-rGO test plate was at least two orders of magnitude greater than that of the control Al test plate, and the graphene layer significantly increased the bandwidth of the maximum phase angle, which indicates a good protective effect of the ultra-thin graphene layer on metal in a corrosive environment. The coating with 40% rGO-FAl complex powders can maintain its appearance after 500 h of salt spray corrosion testing. In contrast, the color of the coating with the original aluminum powders changed after only 300 h.