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 an acid treatment. In order to evaluate the effects of sintering additives on the mechanical properties of the composites, we employed three sets of the composites having different sintering additives. Mechanical properties of the MWCNT-based alumina composites were dependent mostly on the type of sintering additives. The composites with magnesia sintering additive, having 0.9vol.% acid-treated MWCNT, showed a higher bending strength (689.6MPa) and fracture toughness (5.90MPa・m^<1/2>), than those of the composites with silica sintering additive.
