Influence of the vol% SiC on properties of pressureless Al2O3/SiC nanocomposites

Al2O3/SiC nanocomposites were prepared by pressureless sintering with micron-sized Al2O3 powders whose average ranged 5 µm in d50 and nano-sized SiC powders whose average ranged 80 nm in d50 as raw materials. The combined powders were then ball-milled in iso-propanol alcohol and then, the slurry was freeze granulated. Compressed samples were prepared by cold isostatic pressing of the granules. Pressureless sintering was carried out in an argon atmosphere at 1750℃ for 4 h. The physical and mechanical properties, including density, hardness and fracture toughness of specimens as well as microstructural investigations were analyzed. The results showed that by increasing vol% of SiC up to 5, hardness and fracture toughness were improved, whereas by increasing more than 5 vol% of SiC, hardness increased but fracture toughness decreased. The scanning electron microscope micrographs showed that, SiC nanoparticles inhibited the grain growth of Al2O3 and reduced the matrix grain size accordingly.