Soaking method for fabrication of alumina-based nanocomposites

Previously published research proposed strengthening and toughening mechanisms of nanocomposites based on dislocation activities even in brittle ceramics. We reported that an intra-type nano-structure could only have the potential to improve strength and fracture toughness due to dislocations formed around the dispersed particles. In this research, nickel dispersed alumina nanocompsoites were fabricated using a novel soaking method, based on the developed strengthening and toughening mechanisms. Commercially available γ-alumina powder with high porosity was used as the starting materials. Secondary, particles were introduced into the nano-pores of the porous γ-alumina powder using a soaking method, where the alumina powder was soaked in a nickel nitrate solution under vacuum. During pre-calcination, nickel oxide particles were generated inside the nano-pores. The alumina powders were then reduced under hydrogen atmosphere to obtain nano-sized metallic nickel inside the γ-alumina grains. The alumina–nickel composite powders were sintered by pulse electric current sintering (PECS) technique with α-alumina seeds. The mechanical properties of specimens were investigated, such as density, three-point strength, and fracture toughness. The maximum strength of the alumina–nickel nanocomposites was 984 MPa after being sintered at 1450 °C with α-alumina seeds, where the specimen size was 2 mm × 2 mm × 10 mm. The maximum fracture toughness was 5.5 MPa m1/2 after being sintered at 1350 °C with seeds measured by the single edge V-notched beam method.