Effect Of Additives On Sintering And Mechanical Properties Of Zirconia

Structural ceramics are widely used in more and more fields,including biomedicine,electronics industry,aerospace and so on.Zirconia（ZrO₂）is an important ceramic material because of its characteristics of bioinertness,high hardness,excellent thermal shock resistance,good wear resistance and high fracture toughness.However,the sintering temperature of ZrO₂is high,and there is a transformation from tetragonal phase to monoclinic phase during the cooling process,accompanied by a volume change of about 5%,which is easy to introduce phase transition cracks,which seriously limits its large-scale commercial application.The addition of a small amount of Y₂O₃can stabilize part or all of the high temperature tetragonal phase or cubic phase to room temperature;combined with the application of sintering aids,it can greatly reduce the sintering temperature and preparation cost,and further expand its application range.However,the amount of sintering aid system reported in the literature and the performance of the sintered product are quite different,and it is impossible to directly compare the effects of different sintering aids on the material properties,which will affect the further optimization of the sintering aid system and the performance of ZrO₂.further improvement.Therefore,this paper adopts the dry pressing forming method combined with atmospheric pressure sintering technology,taking 3mol%Y₂O₃stabilized ZrO₂zirconia（3YSZ）as the research object.The effects of the types and contents of sintering additives such as CeO₂,La₂O₃,SiO₂,Al₂O₃and NiO on the density,phase,mechanical properties and microstructure of 3YSZ ceramics were studied in detail,so as to obtain systematic data.This paper provides a reliable performance database for machine learning and other artificial intelligence methods to optimize the sintering additive system and improve the performance of 3YSZ.The main research contents and results are as follows:（1）3YSZ ceramic materials with different contents of CeO₂were prepared by atmospheric sintering.The experimental results show that the introduction of CeO₂significantly improves the mechanical properties of 3YSZ ceramic materials.When the sintering temperature was 1450℃,the holding time was 2h,the addition of CeO₂was 0.1wt%,the mechanical properties of 3YSZ ceramic materials were the best.The relative density,three-point bending strength,fracture toughness and Vickers hardness reached 98.15%,932.86MPa,20.30MPa·m^1/2and 13.62Gpa,respectively,which were 1.16%,38.08%,50.93%and 9.66%higher than those of the control group.（2）In this paper,3YSZ ceramic materials with 0.1wt%CeO₂were prepared at different sintering temperatures of 1400℃,1450℃,1500℃and 1550℃for the same holding time of2h.The experimental results show that the optimum sintering temperature was 1450℃,the number of pores in the material is small,the size of pore size was small,the arrangement of grains was close,the density was good,and the mechanical properties were enhanced most significantly.（3）Based on the optimum sintering temperature,the effects of different sintering additives such as La₂O₃,SiO₂,Al₂O₃and NiO on the microstructure and mechanical properties of 3YSZ ceramics were studied,and the mechanism of action was analyzed.It was found that 3YSZ ceramic material with 0.5wt%NiO showed the best mechanical properties,and the relative density,three-point flexural strength,fracture toughness and Vickers hardness reached 97.66%,699.81MPa,13.03 MPa·m^1/2and 13.17GPa,respectively.At the same time,the experimental results show that the addition of La₂O₃,SiO₂,Al₂O₃and NiO can significantly improve the relative density,bending strength and Vickers hardness of 3YSZ ceramic materials,except that the addition of SiO₂will reduce the Vickers hardness.The fracture toughness of 3YSZ ceramic materials can be significantly improved by the addition of La₂O₃,and the fracture toughness of 3YSZ ceramic materials can be significantly reduced by the addition of SiO₂,Al₂O₃and NiO.