Characterization of alumina/molybdenum Nanocomposites
Seong-min CHOI, Katsuhiro ISHIKAWA, Shinobu HASHIMOTO and Hideo AWAJI
Abstract: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 30 Mpa for 5 min in vacuum in the temperatures ranging from 1250Ž to 1550 Ž. Three-point bending and fracture toughness (SEVNB) tests were carried out on the specimens of 2~2~10 mm3 in size. The results showed that the maximum values of the fracture strength and the fracture toughness were 860 Mpa and 5.22 MpaEm1/2 for the specimens sintered at 1450 Ž, respectively. The specimens with the highest fracture toughness were then annealed at 800Ž, 900Ž, and 1000 Ž from 0 to 10 min. The fracture toughness of the specimen annealed at 800 Ž for 10 min increased from 5.22 to 5.67 MpaEm1/2. The strengthening and toughening mechanisms of the alumina-Mo nanocomposites were discussed with emphasis on dislocation activities. Key Words:Nanocomposites, Alumina, PECS method, Fracture toughness, Annealing