Abstract
We proposed strengthening and toughening mechanisms of nanocomposites based on dislocation activities in brittle ceramics. We took notice that an intra-type nana-structure could only have the potential to improve strengthand fracture toughness due to dislocations formed around the dispersed particles. In this work, we prepared nickel dispersed alumina composites powders with 10 wt% α-alumina as a seeds using a novel soaking method and sintered by pulse electric current sintering (PECS) technique. The maximum strength of the alumina-nickel nanocomposites was 984 MPa after being sintered at 1450 °C, where the specimen size was 2x2x10 mm 3 . The maximum fracture toughness was 5.5 MPa.m 1 / 2 after being sintered at 1350 °C measured by a single edge V-notched beam (SEVNB) method. The specimen sintered at 1350 °C with seeds was carried out heat-treatment under Ar atmosphere. We changed heat-treatment temperature from 800 °C to 1000 °C and keeping time at that temperature from 0 min to 10 min. The value of fracture strength after heat-treatment showed similar that with before heat-treatment. However, the fracture toughness was remarkably increased to 7.6 MPa.m 1 / 2 in annealed specimen at 800 °C for 5 min. This fracture toughness value showed about 2 times larger than that of monolithic alumina.
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