Flexural strength evaluations and fractography analyses of slip cast mesoporous submicron alumina

Mesoporous submicron alpha-Al2O3 green compacts were fabricated using slip casting of ultrafine alumina powders. The pre-sintered samples were sintered in air atmosphere at 1300 degrees C, 1350 degrees C, 1400 degrees C, and 1500 degrees C to obtain a variety of grain morphologies namely submicron equiaxed and micro rod structures. The resulting grain diameters lie between similar to 270 nm and similar to 1590 nm and total porosity fraction between 0.05% and 13%. The room temperature flexural strength (sigma) evaluations and fractography analyses of sintered alumina samples were performed. It was observed that the total porosity fraction dictates the flexural strength as compared to grain diameter. Further, it was found that the flexural strength exhibited a decreasing trend for an increase in the total porosity fraction, and proved to be a better effective parameter than open porosity fraction. The fractography analyses suggest that samples sintered at 1300 degrees C and 1350 degrees C predominantly underwent intergranular fracture, while those sintered at 1400 degrees C and 1500 degrees C underwent a mixture of intergranular and transgranular fracture.