Diluted magnetic semiconductors Zn_1−xFe_xO nanoparticles with different doping concentration (x = 0, 0.01, 0.05, 0.10, and 0.20) were successfully synthesized by hydrothermal method. The crystal structure, morphology, and optical and magnetic properties of the samples were characterized by X‐ray diffraction (XRD), energy dispersive spectrometer (EDS), high‐resolution transmission electron microscopy (HRTEM), Raman scattering spectra (Raman), photoluminescence spectra (PL), and the vibrating sample magnetometer (VSM). The experiment results show that all samples synthesized by this method possess hexagonal wurtzite crystal structure with good crystallization, no other impurity phases are observed, and the morphology of the sample shows the presence of ellipsoidal nanoparticles. All the Fe³⁺ successfully substituted for the lattice site of Zn²⁺ and generates single‐phase Zn_1−xFe_xO. Raman spectra shows that the peak shifts to higher frequency. PL spectra exhibit a slight blue shift and the UV emission is annihilated with the increase of Fe³⁺ concentration. Magnetic measurements indicated that Fe‐doped ZnO samples exhibit ferromagnetic behavior at room temperature and the saturation magnetization is enhanced with the increase of iron doping content.

Graphene–nickel (G–Ni) composites were in situ fabricated by a powder metallurgy method. The effects of graphene content on the tribological behavior of G–Ni composites were investigated. The tribochemistry and structural evolution of graphene were analyzed by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy to understand the lubricating role of graphene in the G–Ni composite. The results show that graphene protects the nickel matrix from severe oxidation at the expense of its oxidation during sliding friction. Graphene on the friction interface transforms from a structure with less defects to a disordered amorphous structure. Polymeric segments are also generated by the tribochemical reactions of graphene. The formation of the tribofilms containing amorphous carbon and polymers is responsible for the self-lubricating behavior of the G–Ni composites.