Preparation And Properties Of TiN-Al₂O₃ Composites

T1N-Al₂O₃ powders were prepared by wet ball milling with micrometer TiN, Al₂O₃ powder and alcohol as starting materials. The sintered bodies were prepared by pressureless sintering process at the sintering temperature of 1700℃,1750℃,1800℃ for 3 hours in the nitrogen atmosphere. The influences of sintering temperature and TiN content on the mechanical properties and electrical conductivity of TiN-Al₂O₃ composites were studied.Experimental results show that the mechanical properties of the composite increases with improving sintering temperature and A composite of 40Vol%TiN-Al₂O₃ with 518.1MPa bending strength and 4.972 MPa·m^1/2 fracture toughness was obtained at the sintering temperature of 1750℃ for 3 hours. The mechanical properties of the composite increases with increasing amount of TiN, while the resistivity ofcomposites decreases and reaches to a value of 1.34×10³ Ω·cm for the composite with 40Vol %TiN.The addition of an electroconductive second phase to the matrix was tolower the electrical resistivity drastically .The electric conduction mechanism of TiN-Al₂O₃ composite can be explained by using the therory perclation. The therory perclation think that TiN-Al₂O₃ compound material belongs to the increase conducting material. When the TiN pellet content surpasses the volume percolation, the material electronic resistivity suddenly will reduce, the material will become the conductor by the insulator. The material electronic resistivity reduces along with the TiN pellet content increase.The material electronic resistivity and the TiN pellet contentrelations divides into three stages. The first stage (0% ～ 10%) along with the TiN content increase, the material electronic resistivity is dropping, but material still for insulation material; The second stage(10% ～ 20%) along with the TiN content increase, the material electronic resistivity suddenly drops; The third stage (20% ～ 40%)along with the TiN content increase, the electronic resistivity dropsslowly. Through the computation material the critical percent content of TiN is 17.24%.The SEM analysis shows that the TiN are distributed uniformly among the crystal boundary of Al₂O₃ matrix and bonded together after sintered to form a net-like structure that plays a role to restrain Al₂O₃ grains to grow up and furthermore result in an enhancement of the mechanical properties of TiN-Al₂O₃ composites. The TiN grains are distributed uniformly among the crystal boundary of Al₂O₃ matrix matrix and bonded together after sintered to form a net-like structure that plays a role to restrain Al₂O₃ grains to grow up and furthermore result in an enhancement of the mechanical properties of TiN-Al₂O₃ composites. Toughening effect markedly enhanced with increasing TiN content.