Preparation And Properties Of Pressureless Sintering Al₂O₃ Based Multiphase Ceramics

In this paper,TiN_p/Al₂O₃（ZrB₂/Al₂O₃）multiphase ceramics with different additive content,sintering process and TiN（ZrB₂）content were prepared by tape casting and calendering forming and pressureless sintering.The rheological properties of the slurry were tested by rheometer.The phase and microstructure of multiphase ceramic materials were analyzed by XRD and SEM.The mechanical properties of multiphase ceramic materials were evaluated by Vickers indentation and Nano-indentation.The effect of the content of conductive phase on the resistivity of multiphase ceramic materials was studied by means of electrical resistance meter and the mechanism of electrical conductivity was discussed.It was found that the density of TiN_p/Al₂O₃multiphase ceramics prepared by tape casting was low,which was about 50%.The higher content of organic matter made the samples deform greatly after sintering,which was not conducive to the subsequent performance test and application.The density of TiN_p/Al₂O₃multiphase ceramics prepared by calendering forming was about 62%,and the best properties of the materials could be achieved:Vickers hardness 2.2GPa,elastic modulus134.7GPa,resistivity 0.7Ω·cm.The relative density of TiN_p/Al₂O₃multiphase ceramics prepared by different sintering processes was about 65%,and the optimal properties were:Vickers hardness 12.7GPa,elastic modulus 313.2GPa,resistivity 0.2Ω·cm.Mechanical properties experiments found that the relative density of TiN_p/Al₂O₃multiphase ceramics prepared with different TiN contents was about55%.The optimal properties were:Vickers hardness 1.9GPa,elastic modulus104.2GPa,resistivity 0.04Ω·cm.The relative density of ZrB₂/Al₂O₃multiphase ceramics prepared with different ZrB₂content was about 52%,and the optimal properties were:Vickers hardness 1.7GPa,elastic modulus 65.0GPa,resistivity10¹⁰Ω·cm.The electrical properties of TiN_p/Al₂O₃multiphase ceramic materials showed that the content of TiN had a significant effect on the resistivity.When the content of TiN was low,the resistivity of the material was higher,which was 10¹⁰Ω·cm,and it was in the insulator state.With the increase of TiN content,the resistivity dropped rapidly to 0.04Ω·cm,which was in semiconductor state.When TiN content was further increased,the resistivity of the material decreased slowly and was about to enter the conductor state.The results were in agreement with the seepage theory.When the content of TiN exceeded the percolation threshold,the conductive path was formed and the resistivity decreased rapidly.