Research On The Preparation Of ZrO₂ Ceramic Flake

With a high melting point,boiling point and hardness,Zirconium oxide(ZrO₂) is a refractory material that exhibits insulating at low temperature and conducting at high temperature.ZrO₂ toughened ceramics discovered in 1970's have greatly enhanced the mechanical properties of ZrO₂ materials,leading to a widely application in engineering ceramics field.In this study,3%mol yttria stabilized tetragonal zirconia polycrystal(3Y-TZP) ceramics were fabricated by cold isostatic pressing after dry extrusion molding under different conditions.The effects of the procedure of pressureless sintering and hot isostatic pressing(HIP)on densification,microstructure and mechanical properties were studied.X-ray diffraction(XRD),scanning electron microscopy (SEM)and material microscope were employed to characterize the phases,grain size and microstructure of 3Y-TZP ceramics.By testing and analyzing systemically, an optimum densification procedure for sintering 3Y-TZP ceramics was obtained. The results of relative densities,micro-hardness and fracture toughness showed that 3Y-TZP ceramics under the optimum sintering procedure present good performances.For the sintered process,four 3Y-TZP powder compacts were pressureless sintered at temperatures 1300℃for 4h,1350℃for 4h,1400℃for 2h and 1450℃for 2h,respectively.Compared the densification and the mechanical properties of the four sintered 3Y-TZP ceramics,sintering at 1350℃for 4h is found to be the optimum approach.In order to get an optimum HIP sintering procedure,the specimens were pre-sintering at 1350℃for 4h,followed by sinter-HIP route under different pressures and temperatures.The results of densification and mechanical properties of specimens indicated that sintering at 1300℃for 1h under 150MPa is the optimum HIP sintering procedure.The performance testing results showed that the 3Y-TZP ceramics pressureless sintered temperature at 1350℃for 4h have good mechanical properties,of which fracture toughness and Vickers hardness is 18.7MPa·m^1/2and 13.7 GPa,respectively. After subsequent HIP sitering with the predetermined optimum procedure,the fracture toughness and Vickers hardness of 3Y-TZP transformation toughened ceramics is 17.7MPa·m^1/2and 14.2GPa,respectively.The effect of the sintering parameters on the properties of 3Y-TZP ceramic demonstrated that the fracture toughness and Vickers hardness of 3Y-TZP ceramics were determined by the micro-structure of materials and ZrO₂ transformation toughening.During the rupturing of ZrO₂ transformation toughening ceramics,the transformation of t-ZrO₂ to m-ZrO₂ is also influenced by grain size.With definite starting powder particles,the t-ZrO₂ transformability controlled by optimize sintering parameter or over-sintering anneal under high temperature plays an important role in achieving excellent mechanical properties of 3Y-TZP transform toughened ceramics.