PREPARATION OF NANO AND MICRON SIZED ZrO_2 DISPERSED A1_2O_3 CERAMIC COMPOSITES AND STUDY THEIR HARDNESS AND FRACTURE TOUGHNESSES

摘要

The present study aims at improving the fracture toughness of bulk alumina ceramics by incorporating micron and nano sized zirconia particles. Al_2O_3 - ZrO_2 ceramic composites were prepared with lvol% micron sized and lvol% nano sized ZrO_2 particles by uniaxial pressing and sintering at 1500°C for soaking time period of 3hr, 6hr and 9hr. The mechanical properties viz. hardness and fracture toughness of the composites were investigated. It was found that the fracture toughness of the nano/micron sized zirconia particle dispersed Al_2O_3 composites was significantly improved compared to monolithic Al_2O_3. The alumina composites with lvol% nano sized ZrO_2 particles sintered at 1500°C for 6hr show highest fracture toughness of 5.76 MPam~(1/2), while the maximum fracture toughnesses of only alumina and alumina composites with lvol% micron sized ZrO_2 particles are 5.29 and 5.35 MPam~(1/2) respectively. The toughening mechanisms of the ceramic composites are discussed.