Structure Control and Thermal Stability of Tetragonal Zirconia by Post-HIPing Method

点击翻译按钮获取中文摘要

Improvement of thermal stability and control in the microstructure of tetragonal zirconia polycrystals were studied by the application of the postsintering hot isostatic pressing method. The goal of the present study is to obtain the fundamental results on fabrication of the yttria and ceria doped tetragonal zirconia polycrystals ((Y,Ce)-TZP), (Y,Ce)-TZP/Al_2O_3 composites, ceria doped tetragonal zirconia polycrystals (Ce-TZP) and Ce-TZP/Al_2O_3 composites with high fracture strength, high fracture toughness, high thermal stability and high thermal shock resistance by controlling the microstructure of these ceramics.The present tetragonal zirconia based ceramics were fabricated at 1400-1500ﾟC for 10hr in air,,and then postsintering hot isostatic pressing method was applied at 100-15OMPa and 1300-1600ﾟC for lhr in order to decrease the flow size and to control the microstructure of these sintered bodies. From the results on changes in the crystalline phase and microstructure and degradation of fracture strength of TZP ceramics, the thermal stability of zirconia could be improved by decreasing the grain size of zirconia, dispersing Al_2O_3 and alloying with CeO_2. Thermal stability of Y-TZP ceramics could be perfectly controlled by alloying with more than 12 mol% CeO_2, but it significantly degradated the sinterability, and fracture strength . The mechanical properties of (Y,Ce)-TZP could be improved by dispersing Al_2O_3 particles. Post-HIP method was useful to densify the (Y,Ce)-TZP/Al_2O_3 composites and to improve their mechanical properties. Postsintering hot isostatic pressing was very useful to densify Ce-TZP/Al_2O_3 composites without grain growth and to improve the fracture-strength and thermal shock resistance. It is found that the tetragonal ZrO_2 based ceramics with thermal stability, high fracture strength and good thermal shock resistance are easily fabricated by post-HIPing method.