An evaluation of Al2O3-ZrO2 composites produced by coprecipitation method

The objective of this work is to produce Al2O3-ZrO2 composite from nano-sized powders processed by coprecipitation method. Al2O3 and mixture of Al2O3 + 10 wt.% ZrO2 precipitated successfully by chemical route from aluminum sulfate and zirconium sulfate were pressed under uniaxial compression of 170 MPa and sintered at 1600 degrees C for 1 h. SEM investigations revealed that, pure alumina sample has a microstructure with coarse grains which anisotropically grown up to 30-40 mu m in size. In alumina-zirconia composite, the structure consists of very fine equiaxed grains of typically 2 mu m in which zirconia precipitates were uniformly dispersed. By adding zirconia to alumina, hardness and indentation fracture toughness were increased from 11.6 GPa to 16.8 GPa and from 3.2 MPa m(1/2) to 4.9 MPa m(1/2), respectively. Improvement in fracture toughness was attributed to bridging effects of zirconia particles as well as transformation toughening. (C) 2010 Elsevier B.V. All rights reserved.