Preparation Of ZTA Composites By Nanotechnology

Starting from the relatively inexpensive inorganic salts, production of ultra fine zirconia/alumina powders through precipitation was studied systematically. Using the self-prepared powders, ZTA composites were fabricated the reactive ability of powders and relationship between microstructure and mechanical property was analyzed. Toughening mechanism of materials was studied also.Using the ammonium carbonate hydroxide (AHC) as precipitant to prepare the oxide powders, the dispersal basic carbonate precursors were obtained and hard agglomeration from hydroxide condensation reaction could be avoided. The powders were characterized by the testing methods such as XRD, SEM, TEM, LDS. It was founded that the dripping speed of salt solution was the key factor to preparation of powders. In addition, 5wt%α-Al₂O₃ seeds can lower formation temperature of alpha alumina. Through adding little dispersant and controlling the dripping speed below 2/min, well dispersed nanopowders with a mean diameter of about 10nm and a narrow size distribution was produced by calcining the precursor at 1100℃for 2 hour. Noγ-Al₂O₃ andθ-Al₂O₃ formed in calcinations and the powders had excellent sintering reactivity. The relative density of specimen got to 98.5% after sintering pressurlessly the green compacts at 1550℃. The sintering compacts have fine and uniform microstructure. The small grains are located between or within large grains revealing the uniform dispersion of zirconia grains in the alumina matrix. From experiment results, it was founded that higher sintering temperature was harm to the ZTA mechanical properties.The dramatic influences of stable reagent amounts on the properties of ZTA composites were analyzed. They effected the phase transformation of zirconia during sintering and stressing greatly. The microstructure and densification of ZTA ceramics was changed at the same time, so their mechanical properties were different. In 0Y-ZTA ceramics, most of zirconia transformed to monoclinic phase during powders process and ceramic process. Micro-crack toughening and residual stress toughening mainly contributed to the mechanical property 0Y-ZTA . There were a lots of pores in the 6Y-ZTA and 12Ce-ZTA, so their mechanical properties were less than 3Y-ZTA ceramics. The martensitic transformation from tetragonal to monoclinic phase occurred in all ZTA ceramics on the fracture surface.The effects of zirconia contents on the properties of ZTA composites were...