We report the mechanical properties of multi-walled carbon nanotube (MWCNT)/alumina composites made with a pristine MWCNT and an acid-treated version that have nanoscale defects on their surfaces from the acid treatment. Microstructural observations revealed that a homogeneous distribution of MWCNTs in the alumina matrix was achieved by a novel processing approach based on the precursor method for the synthesis of alumina and acid-treated MWCNTs. An interesting geometric structure was observed between individual MWCNT and alumina matrix. The nanodefect on the acid-treated MWCNT was filled up with alumina crystal, wiuich may be intruding into the nanodefect during grain growth The addition of only 0.9 voL% acid-treated MWCNTs to alumina resulted in 27% and 25% simultaneous increases in bending strength (689.6 ± 29.1 MPa) and fracture toughness (5.90 ± 0.27 MPam^<1/2>), respectively.
