Characterization of Alumina/Molybdenum Nanocomposites( Ceramic Materials)

We fabricated alumina/molybdenum (Mo) nanocomposites. To prepare very fine Mo powder, molybdenum oxide (MoO3) powder was dissolved in 28% ammonia solution. Alumina powder was then mixed with the neutralized MoO3 solution in ethanol using a ball mill. After drying, a pulse electric current sintering method was used for sintering the mixed powder at 30MPa for 5min in vacuum in the temperatures ranging from 1250°C to 1550°C. Three-point bending and fracture toughness (SEVNB) tests were carried out on the specimens of 2 × 2 × 10mm in size. The results showed that the maximum values of the fracture strength and the fracture toughness were 860MPa and 5.22MPa · m1/2 for the specimens sintered at 1450°C, respectively. The specimens with the highest fracture toughness were then annealed at 800°C, 900°C, and 1000°C from 0 to 10min. The fracture toughness of the specimen annealed at 800°C for 10min increased from 5.22 to 5.67MPa · m1/2. The strengthening and toughening mechanisms of the alumina-Mo nanocomposites were discussed with emphasis on dislocation activities.