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.