Fabrication of Al/Al2O3/ SiC/graphene hybrid nanocomposites from Al-dross by powder metallurgy: Sinterability, mechanical and electrical properties

Abstract

The recycling of industrial wastes instead of their burial disposing is necessary for maintaining the environment. In the current research, aluminum dross waste was utilized for preparing sintered Al/Al2O3 hybrid composites reinforced with different amounts of SiC and graphene up to 8 and 4 wt %, respectively. To obtain nanocomposite powders, aluminum dross and reinforcing materials were milled by high energy ball milling for 10 h. The particles' shapes and sizes of prepared nano powder were characterized by transmission electron microscope while the phase composition, crystallite size, lattice strain and dislocation density were investigated by X-ray diffraction technique. To fabricate sintered hybrid composites, the prepared nano powders were pressed and sintered at 1000 and 1200 °C. The physical properties in-terms of bulk density and apparent porosity of sintered composites were determined by liquid-displacement technique. The microstructure and phase composition were examined by scanning electron microscopy and X-ray technique, respectively. Furthermore, compressive strength, microhardness, wear resistance and dielectric properties were investigated in details. Also, pulse-echo technique was used to determine the elastic moduli. The results showed that the particle size of milled aluminum dross (Al/Al2O3) powder which contains 8 wt% SiC and 4 wt% graphene is 43.8 nm while its crystal size is equal 19.2 nm. Generally, all physical, mechanical and electrical properties were improved after increasing the sintering temperature from 1000 to 1200 °C and the reinforcement amounts. When this batch sintered at 1200 °C, the microhardness, compressive strength and elastic moduli increased by about 142.5, 44.8 and 46% while the wear rate was reduced by about 27% as compared to the composite that contain zero SiC and graphene. The increasing of SiC and graphene in Al/Al2O3 composites as well as sintering temperature led to positive effect on AC conductivity (σac), dielectric constant and dielectric loss.