Preparation Of Zirconia -Zirconia /Alumina Laminated Composite Ceramics

Zirconia and alumina are widely used as advanced ceramic materials.However,with the development of technology,the market tends to be saturated,and the market competition of ceramic products becomes increasingly fierce.In order to meet the market demand and improve the competitiveness of products,manufacturers put forward higher requirements for the performance of products: high toughness,high strength,high temperature resistance and high thermal shock resistance.As a new type of structural ceramics,layered composite ceramics have been studied by more and more people.At present,the research of zirconia alumina system layered composite ceramics is mainly based on the surface thin layer,about 200-500 ?M.in some high-temperature fields,this structure design can not meet the use requirements,and most of the surface layer is not zirconia but zirconia composite alumina ceramics.Alumina is easy to react under the high temperature of other components.Therefore,the current zirconia alumina layered composite ceramics can not meet the market demand very well.Therefore,this paper mainly studies the zirconia zirconia zirconia / alumina laminated composite ceramics with the surface layer of zirconia.In this paper,some stable zirconia,zirconia?monoclinic phase?,quartz,calcium carbonate,alumina and other raw materials were studied.The biggest factor that affects zirconia zirconia / alumina to realize thick layer composite is that the thermal expansion difference between zirconia and alumina matrix is too large.During the sintering and cooling process,the thermal stress between the layers will lead to the phenomenon of stress concentration at the interface of the layers,which will lead to the spalling of the composite ceramics.According to the above phenomenon experiment,PSZ?FSZ?-ZrO₂ /Al₂O₃ laminated composite ceramics were prepared by adjusting the thermal expansion curve of zirconia / alumina layer and partially stabilized zirconia layer to match each other.Through strength test,XRD,thermal expansion and scanning electron microscope,the content of zirconia and quartz in zirconia /alumina layer,the effect on thermal expansion of zirconia / alumina layer ceramics,the effect of pore forming agent on zirconia ceramics,and the effect on composite results,strength and thermal shock resistance of laminatedcomposite ceramics were studied.The experimental results show that the thick layer composite of PSZ-ZrO₂ / Al₂O₃ can be realized by adjusting the thermal expansion curve of each layer.The experiment of FSZ-ZrO₂ / Al₂O₃ laminated composite ceramics failed because of the great difference of thermal expansion between the fully stable zirconia layer and the alumina layer.It was found that when the formula of PSZ-ZrO₂ / Al₂O₃ laminated composite ceramics was 3Y-PSZ?20g?,Al₂O₃?80g?,3gSiO₂,1.07g CaCO₃,it was close to the thermal expansion of the partially stable zirconia layer,and the composite result was better.It is speculated by XRD and EDS that the ternary system of CaO-Al₂O₃-SiO₂ is formed at high temperature of SiO₂,CaO and Al₂O₃,and then melt into liquid phase.Near the layer interface,the zirconia / alumina layer flows to the zirconia layer by liquid phase mass transfer,so as to eliminate part of the interlaminar stress and make the two layers better combine.During the cooling process,the low thermal expansion materials such as calcium feldspar and mullite are dispersed among the grains,which hinders the contraction stress of alumina acting on the zirconia grains,promotes the transformation of tetragonal zirconia to monoclinic phase,makes the thermal expansion curve of alumina layer approach to zirconia layer,and solves the problems of interlayer cracking and deformation of composite ceramics caused by different thermal expansion.