Synthesis and Characterization of High-Performance, Aluminum/Graphene Nanocomposites for Light-Weighting Applications towards Energy Efficiency Goals

Tailoring structural elements to provide a superior technical performance through using less material is known as light-weighting and is one of the strategies suggested to increase energy efficiency and reduce fuel consumption and harmful emissions. Aluminum (Al) is an indispensable metal in automobile and aerospace industries for its lightweight, corrosion resistance, and high ductility. In this thesis, a nanocrystalline (NC) Al matrix was alloyed with lithium (Li) to further reduce its density, and reinforced with graphene nanoplatelets (GNPs) to enhance its strength and thermal stability, using ball-milling. A comprehensive study was conducted to realize the optimum Al-Li-GNPs nanocomposite in terms of both the milling conditions and the consolidation process. In addition, the effect of the GNPs content on the thermal stability, mechanical properties, and deformation mechanisms of the nanocomposite, was investigated. The optimum Al-Li-GNPs system is synthesized by ball-milling for 8 hours at room temperature, followed by hot pressing and hot rolling. The Al-based nanocomposites are thermally stable up to 773 K through both kinetic and thermodynamic mechanisms. High hardness, tensile yield strength, and compressive yield strength, of 1.52 GPa, 372 MPa, and 403 MPa respectively, in addition to good ductility, were achieved upon the addition of 1.0 wt% GNPs. Strengthening and deformation mechanisms were identified by microscopic investigations which revealed the presence of a high density of dislocations, stacking faults, twinning, and carbide phases. In addition, microscopic investigations revealed the formation of hexagonal platelet-like single-crystal Al-based nanoparticles, which exhibit high plasmonic absorbance. It is believed that the interaction between Al and GNPs under milling conditions initiated the anisotropic growth. The results in this thesis present a novel, thermally stable, ultra-strong, Al-Li-GNPs nanocomposite, and reveals for the first time, the synthesis of plasmonic single-crystal Al-based nanoparticles using a simple ball-milling technique.