Processing and mechanical characterization of Al2O3/Ni and Al2O3/C0 composites by pressureless sintering of nanocomposite powders

Abstract

Al 2 O 3 /Ni and Al 2 O 3 /Co nanopowder mixtures (with 3 vol.% of metallic phase) were synthesized by heterogeneous precipitation method. In order to increase the green strength, polypropylene carbonate (PPC) was used as a binder while preparing green compacts. Uniaxially pressed powder mixtures were sintered at 1550°C for 2 h in a reducing atmosphere. The effects of Ni and Co nanophases on the microstructure and mechanical properties of Al 2 O 3 ceramics were studied by X-ray diffraction, scanning electron microscopy, Vickers indentation technique and three-point bending tests. The metallic phase hindered the densification of alumina matrix, yet hardness values of Al 2 O 3 , Al 2 O 3 /Ni, and Al 2 O 3 /Co composites were comparable. Vickers fracture toughness results indicate that the composites have higher fracture toughness, but the characteristic flexural strength and Weibull modulus are higher for the pure Al 2 O 3 .