Preparation And Mechanical Properties Of Novel Zirconia Ceramics And Composites

Advanced ceramic materials have received increasing attention in many fields because of their excellent properties,especially in new fields such as nuclear energy systems.Because of their harsh working environment,only a few materials can do the job,so new advanced ceramic materials have broad development prospects.It is of great significance to promote my country's nuclear power industry and enhance national defense capabilities.At present,the fourth-generation nuclear power reactors developed in the world put forward higher performance requirements for their core components:high temperature resistance,corrosion resistance and radiation resistance,etc.Zirconia(ZrO₂)matrix composite has become one of the preferred core structural materials for new nuclear power systems because of its excellent properties.At the same time,the thermal conductivity of zirconia ceramics is low,so it is an effective method to improve the thermal conductivity of zirconia ceramics.In order to develop a new type of ZrO₂ matrix composites which better meet the service conditions of the fourth-generation nuclear reactor,a series of ZrO₂ matrix composites were prepared by three different methods of atmospheric sintering,hot pressing sintering and microwave sintering in this paper,and the influence rules of different sintering methods on their properties were explored.The ZrO₂-AlN composites were prepared by microwave sintering,which greatly improved the thermal properties of the ZrO₂ matrix and was expected to be used as fuel elements in high temperature gas cooled reactors.The mechanical properties of ZrO₂-TiC composites were improved by microwave sintering.The structure-activity relationship between the microstructure and thermal properties of the materials was investigated by means of X-ray diffractometer,universal testing machine,scanning electron microscope and thermal conductivity apparatus.The main findings are as follows:1.ZrO₂ matrix composites were prepared by three sintering methods:atmospheric sintering,hot pressing sintering and microwave sintering.The SEM analysis shows that the ZrO₂ matrix composites prepared by microwave sintering method have larger grain size,and the thermal conductivity test shows that the sample obtained by microwave sintering has the maximum thermal conductivity.2.ZrO₂-AlN composites with different AlN content were prepared by microwave sintering.The introduction of AlN significantly improved the thermal conductivity of the ZrO₂-based composite material,and the thermal conductivity,thermal diffusivity and specific heat capacity at 25?reached 41.4 W·m^-1·K^-1,15.2 mm~2·s^-1 and 0.43 J·g^-1·K^-1.3.ZrO₂-TiC composites were prepared from commercial ZrO₂ and TiC by microwave sintering.Y₂O₃ and Al₂O₃ were used as sintering additives to improve the density of the composite,which has good mechanical properties:Vickers hardness of14.8±0.2GPa,fracture toughness of 5.8±0.8 MPa·m^1/2,bending strength of874.3±29.6MPa.At 50?,the thermal conductivity,thermal diffusion coefficient and specific heat capacity of the composite material are increased by 130.4%,81.18%and55.58%,respectively,compared with pure ZrO₂ material.