Microstructure and mechanical properties of oxide based nanocomposites fabricated by spark plasma sintering

In this study, oxide based nanocomposites fabricated by the SPS method, and SEM and TEM study were carried out to understand the microstructure. Also, to understand mechanical and physical properties of the nanocomposite systems, fracture strength, toughness, young's modulus, and hardness measurement were done. Two kinds of oxide based nanocomposites, MgO/SiC and Al₂O₃/SiC nanocomposites, were fabricated by SPS method at 1100 to 1800°C in Ar atmosphere with applied pressure of 30MPa. MgO/SiC nanocomposites, in which nano-SiC particles were dispersed within MgO grains, were improved to the fracture toughness of 3.7MPam^1/2 and strength of 650Mpa, compared to 320MPa and 2.1MPam^1/2, respectively, for MgO monolith. Al₂O₃/SiC nanocomposites were found to consist of the specific microstructures that fine SiC particles less than 200nm were dispersed within Al₂O₃ matrix grains and exhibited the fracture toughness of 5.8MPam^1/2 and strength of 1200MPa, compared to 700MPa and 3.2MPam^1/2, respectively, for Al₂O₃ monolith. These significant improvements of the mechanical properties were contributed to the change of microstructure due to the dispersion of nanometer-size second phase particles.