In-situ formation of Al2O3/Al core-shell from waste material: Production of porous composite improved by graphene

Aluminum dross produced from aluminum industry was used to fabricate Al2O3/Al porous composites. The dross was milled for 20 h to obtain nano powder. The milled material was examined by TEM and XRD. Graphene (up to 4 wt%) was mixed with the dross and utilized to reinforce sintered composites. The milled powders were compacted then fired at various temperatures up to 700 °C. Physical properties in terms of bulk density and apparent porosity for sintered composites were tested using Archimedes method. SEM attached by energy dispersive spectrometer (EDS) was used to inspect microstructure and elemental analysis of sintered composites. Microhardness and compressive strength were also measured. Ultrasonic nondestructive technique was utilized to examine the elastic moduli. Electrical conductivity of sintered composite was also studied. During milling up to 20 h, Al2O3/Al core-shell was in-situ formed with size of 65.9 and 23.8 nm, respectively. The apparent porosity of sintered composites was improved with rising graphene percent while it decreased with increasing sintering temperature. Increasing of graphene mass percent and firing temperature led to remarkable increase in all mechanical properties and electrical conductivity. The maximum compressive strength, hardness, elastic modulus and electrical conductivity were 200 MPa, 1200 MPa, 215 GPa and 1.42 × 10−5 S/m, respectively, obtained for composite sintered at 700 °C having 4 wt% graphene.