Study on the Microstructure and Microhardness Behavior of Reduced Graphene Oxide Reinforced Alumina Nanocomposites

Here, we report the successful development of reduced graphene oxide (rGO) (0.1, 0.3 and 0.9 wt.%) reinforced alumina (Al₂O₃) novel nanocomposites by powder metallurgy route. The composite powder samples were prepared using a high-energy dry planetary ball mill for 2 h under an argon atmosphere. Then, the optimized compacted samples (at 170 MPa for 180 s) having high density were sintered at 1450 °C for 180 min. under an argon atmosphere. The characteristics of the materials have been evaluated to improve microstructure, microhardness, and Young’s modulus of composites. rGO has 4-5 numbers of graphene sheets with an energy band gap of 2.28 eV and a specific surface area of 509.177 m²/g. The rGO retains structural quality before and after making composites with Al₂O₃ samples. The purity of rGO and Al₂O₃/rGO composite samples was confirmed by EDS analysis. While rGO shows peaks of C and O, Al₂O₃/rGO (0.1, 0.3, and 0.9 wt.%) composite samples show peaks of Al, O, and C. Micro Raman analysis establishes the successful formation of composite between Al₂O₃ and rGO. Al₂O₃/rGO (0.1, 0.3, and 0.9 wt.%) composite samples mostly show similar kinds of D, G, and 2D peaks as shown by pure rGO. The outstanding result achieved for the typical Al₂O₃/rGO (0.3 wt.%) sample showed significantly higher microhardness (2488 ± 12 VHN) and Young’s modulus (520 ± 9 GPa) values compared to pure Al₂O₃. The microhardness and Young's modulus values of Al₂O₃/rGO (0.3 wt.%) composite are more than 79% and 31% compared to those observed for pure Al₂O₃. When the rGO amount further increased to 0.9 wt.% in Al₂O₃, agglomeration of graphene sheets developed, which caused degradation of the mechanical property of the composite. The excellent outcome of this work further advances critical applications of Al₂O₃ in various industrial fields.