Investigation of yttria-doped alumina nanocomposites reinforced by multi-walled carbon nanotubes

Nanocomposites of Y2O3 doped Al2O3 reinforced with 2 wt% MWCNTs were fabricated by hot-pressing. The influence of a small Y2O3 addition (300 ppm) on the microstructure and mechanical properties of CNT-reinforced Al2O3 was investigated. The resulting Y2O3 doped Al2O3-CNT nanocomposites showed near theoretical densities (>99%) with an astounding 5 times finer grain size and substantial improvements in the fracture toughness (40%), flexural strength (20%) and hardness (18%) than pure Al2O3, prepared under identical experimental conditions. The Y2O3 addition improved the density of the matrix, eliminated the residual flaws and formed YAG (yttrium–aluminium–garnet) particles at the grain boundaries in the nanocomposites. The submicron YAG particles, together with the CNTs, promoted the Al2O3 matrix to form fine-grained microstructures and altered the fracture mode, thus leading to higher toughness and other mechanical properties. The improved mechanical properties allows for the Y2O3 doped Al2O3-CNT nanocomposites to be used for applications in load bearing structures.