Study On Preparation Technology And Properties Of （TiN,Ti）/ZrO₂ Composite Ceramics

Zirconia ceramics are widely used in the fields of ceramic tools, solid fuel cells and refractory materials due to its high hardness, high temperature conductivity, high temperature resistance and so on. Because of the high insulation performance at room temperature, the application of ZrO₂ ceramics has been limitted in some fields. Therefore, the improvement of conductivity at room temperature is becoming a hot research. According to modified principle of multiphase ceramic material, the TiN with high conductivity and elemental metal Ti were introduced to the ZrO₂ ceramic, ZrO₂ composite ceramics were expected to obtain conductivity at room temperature. In the present paper, the micron grade TiN, Ti and ZrO₂ powders were used as raw materials, （TiN,Ti）/ZrO₂ composite powders could be prepared by wet ball milling mixing, and the composite ceramics were prepared by pressureless sintering under vacuum. At the same time, the effects of two-step sintering and sintering additive ZnO on the properties of ZrO₂ composite ceramics were investigated. The phase composition and microstructure of ZrO₂ composite ceramics were analyzed by XRD, SEM and EDS. The resistivity, density and hardness of ZrO₂ composite ceramics were tested by the resistivity tester, Archimedes drainage method and Vickers hardness tester, respectively. In addition, the conductibility mechanism was discussed. The main conclusions are as follows.TiN can improve the conductivity and hardness of （TiN,Ti）/ZrO₂ composite ceramics,however, the density of it will be reduced. When the TiN content is 20wt.%, the resistivity of ZrO₂ composite ceramics is 7.75×10-2Ω·cm, the hardness is 780HV and the relative density is 93.38%. When the TiN content is 25wt.%, the resistivity can be reduced to 5×10-2 Ω·cm.（TiN,Ti）/ZrO₂ composite ceramics belong to the add-conductive material, and the conductive mechanism is consistent with the theory of percolation.With the increase of sintering temperature, the resistivity of ZrO₂ composite ceramics increases, and the hardness increases first and then decreases. When the sintering temperature is·1200℃,the resistivity of ZrO₂ composite ceramics is 6.46×10-2 , Ω·cm, and the maximum hardness is 780HV when the sintering temperature is 1300℃.By the method of two-step sintering,the density of （TiN,Ti）/ZrO₂ composite ceramics can be increased and the growth of grains can be restrained. It results in the improvement of conductivity and hardness. The best two-step sintering process for preparing ZrO₂ composite ceramics is: sintering at 1300℃ then dropping to 1100℃ and holding for 10h, the resistivity is 3.35×10-22 cm, and the hardness is 815HV.As sintering aids, ZnO has a great effect on the properties of （TiN,Ti）/ZrO₂ composite ceramics. With the increase of ZnO content, the density and hardness of ZrO₂ composite ceramics increases first and then decreases, while the resistivity showed a opposite tendency.When the content of ZnO is 0.5wt.%, the resistivity of ZrO₂ composite ceramics is 6.25×10-2Ω·cm and the hardness is 810HV.