Synthesis of nitrogen-doped graphene and its strengthening effect on aluminium metal matrix composite

Abstract

The present study investigates the potential of nitrogen-doped graphene nanosheets (NDG) as a reinforcing material in aluminum (Al) metal matrix composites. The NDG was synthesized through a mechanochemical process involving solid-state dry ball milling of graphite with melamine. Characterization techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), and Raman spectroscopy were used to evaluate the properties of the NDG. For the first time, NDG was employed as a reinforcing material to improve the wettability, minimize the formation of aluminum carbide, and enhance the strength through strong interfacial bonding. The ultimate tensile and compressive yield strengths of Al/NDG composites were found to be 124% and 67% higher, respectively, with only 0.2 wt% NDG content. Furthermore, the tensile strength of the 0.2 wt% NDG/Al composite was found to be 72% higher than that of the 0.5 wt% graphene/Al composite. The fractured surface of the Al/NDG composite was investigated by XRD and FESEM techniques. XRD analysis revealed the presence of low-intensity peaks of aluminum nitride (AlN) and no evidence of aluminum carbide. The tribological properties of NDG were studied through wear rate and coefficient of friction (COF) measurements. The results showed a decrease in COF by 45% with an increase in NDG concentration from 0.1 to 0.5 wt%, and a decrease in wear rate by 25% and 71% for the same NDG concentration range. These results provide insight into the potential of NDG as an additive to improve tribological properties in aluminum-based composites. Further research is needed to understand the underlying mechanisms and optimize the performance thoroughly.