AUTO IGNITION SYNTHESIS AND CONSOLIDATION OF AL2O3-ZRO2 NANO NANO COMPOSITE POWDERS/

An ''Auto Ignition'' technique was utilized in synthesizing Al2O3-ZrO2 powders with nano/nano microstructure. The process used the correspon ding nitrates as oxidizers and urea as the fuel, The as-synthesized po wders were characterized by x-ray diffraction and transmission electro n microscopy. It was observed that the microstructure consisted of cry stallites of Al2O3 and ZrO2, both of which were nanocrystalline. As op posed to the other nanocomposite ceramics, this feature of the microst ructure classifies the present powders as nano/nano type. This nanocry stallinity of the microstructure (crystallite size less than 100 nm) w as maintained even after a soaking at 1200 degrees C for 2 h. Since th e microstructure is stable at high temperatures, it was possible to de nsity the powders by hot isostatic pressing at 1200 degrees C, The pro duct was 99% of the theoretical density and maintained nanocrystalline grain size. The average hardness and toughness values, as determined by an indentation technique, were 4.45 GPa and 8.38 MPa.m(1/2), respec tively. These values represent evidence of ductility in these composit es since transformation toughening was ruled out in this case. The pot ential application of these results is expected to be in net shape def ormation forming of ceramics.