Fabrication of toughened alumina nanocomposites using γ-alumina powder

To improve fracture strength and fracture toughness in ceramic materials, we focused our attention on an intra-type structure of nanocomposites. We proposed new processing method for fabricating intra-typenanocomposites. In this work, Al2O3/Ni nanocomposites were fabricated using a soaking method and sintered by PECS(Pulse Electric Current Sintering) method. We also estimated seed effects on this system. Seeded nanocomposites showed high fracture strength and higher fracture toughness than non-seeded nanocomposites and monolithic alumina. The fracture strength of the seeded nanocomposites was more than 800MPa in all sintering temperature range. The maximum value of the fracture toughness was 5.5 MPa.m(1/2) for the specimen sintered at 1350 degrees C. The sintered specimens with high fracture strength and high fracture toughness were annealed from 800 degrees C to 1000 degrees C for 0 to 10 min. The specimen annealed at 800 degrees C for 5 min showed the highest fracture toughness of 7.6 MPa-m(1/2). This value is two times higher than that of the monolithic alumina.