Preparation Of High Performance Magnesia Partially Stabilized Zirconia Structural Ceramics And Research Of Sintering Kinetics

Magnesia partially stabilized zirconia?Mg-PSZ?has excellent high temperature strength and ageing resistance.As a structural ceramic,excellent mechanical properties are often an important basis for evaluating their application value.Understanding the evolution of the microstructure during sintering process plays a crucial role in the preparation of high performance ceramic materials.In order to study the influence of MgO content on properties of Mg-PSZ ceramics and sintering kinetics of Mg-PSZ.In this work,Mg-PSZ powders are prepared by coprecipitation,and zirconium oxychloride,magnesia and ammonium hydroxide are used as raw materials.And then,commercial MgO-ZrO₂ powders are used as raw materials,and the influence of sintering temperature,pressureless sintering and thermal isostatic sintering on Mg-PSZ ceramic properties are investigated.Through the above research,the following conclusions are drawn:1.When the content of MgO is 10 mol%,the bulk density and Vickers hardness of ceramics are reached 5.51 g/cm3 and 8.29 GPa respectively.Excessive MgO will lead to Mg2+segregation,which not only inhibits the sintering of materials,but also improves the relative content of m-ZrO₂ in samples.It will limit the mechanical properties of Mg-PSZ ceramics.2.During the intermediate sintering stage,the grain boundary diffusion is the dominant densification mechanism for Mg-PSZ ceramics and the activation energy is 201 kJ/mol.Along with increasing of sintering temperature,the grain growth is mainly controlled by three mechanisms which are normal grain growth,abnormal grain growth and solid solution drag-controlled grain growth,respectively.The corresponding apparent activation energies are 82.31 kJ/mol,470.6 kJ/mol and 365.8 kJ/mol.The kinetics equation of grain growth is as follows:G²=6.31 × 106×t×exp?-8.231 × 104/RT?nm6 × h-1G¹=6.31 × 106×t×exp?-47.06 × 104/RT?nm6 × h-1G³=6.31 × 106×t×exp?-36.58 × 104/RT?nm6 × h-13.Along with increasing the sintering temperature,the bulk density and strength of Mg-PSZ ceramics which are prepared from commercial MgO-ZrO₂ powders are increased first and then decreased.When the temperature is 1600?,the relative content of m-ZrO₂ in the samples is minimum?18.33%?,bulk density is maximum?5.63 g/cm3?,strength of samples is maximum?556.1 MPa?,and the coefficient of thermal expansion is lowest and the material has the best thermal shock resistance.4.The bulk density and Vickers hardness of Mg-PSZ ceramics can be improved by hot isostatic sintering,however,it limits the growth of precipitates in samples and limit the mechanical properties of Mg-PSZ ceramics.When Mg-PSZ is sintered by hot isostatic pressure,the bulk density and Vickers hardness of the samples are reached 5.71 g/cm3 and 9.38 GPa,while the strength is decreased from 556.1 MPa to 531.0 MPa.