| The synthesis of TiN by carbothermal reduction and nitridation of TiO2 was systematically studied by means of thermodynamic analysis, XRD, SEM and TG-DTA. The mechanism of carbothermal reduction and nitridation was expounded. The continuous all-isothermal thermogravimetric method was proposed. The kinetics for the carbothermal reduction and nitridation of TiO2 were researched by this method. The influences of technique factors on the process were discussed in detail. The titanium nitride powder was fabricated in small batches, and the properties of the titanium nitride powder were characterized by the methods of XRD, SEM and so on. Finally, the TiN-Al2O3 composite was fabricated.The thermodynamic analysis shows that the stability domains of intermediate oxide phase and products as well as the starting temperature of carbothermal reduction and nitridation reaction have relations to the temperature in the furnace, the partial pressure of nitrogen and monoxide carbon. With increasing the partial pressure of N2 and decreasing that of CO, the starting temperature of the reaction decreases. Therefore, during the process of synthesis of titanium nitride and titanium carbide, the measurements to decrease the starting temperature of reaction includes: 1) increasing the partial pressure of N2, 2) decreasing the partial pressure of CO by increasing the flow rate of inert gas or vacuumizing the furnace.The reaction sequence of the carbothermal reduction and nitridation of TiO2 was systematically researched by the thermodynamic analysis. The results show that: In a nitrogen-containing atmosphere, the Ti4O7 is the most stable intermediate oxide phase when the temperature is lower than HOOK; while the Ti3O5 is the one when the temperature is higher than HOOK. In a nitrogen-free atmosphere, the Ti2O3 is the most stable intermediate oxide phase when the temperature is lower than 1310K; the Ti3O5 is the one when the temperature is higher than 1310K. This conclusion was accordance with the experimential results. The results show that the TiOxNy phase forms at lower temperature. And the nitrogencontent in the TiOxNy phase increases with the increasing of the synthsis temperature, while the oxygen content in the TiOxNy phase decreases and reaches to a value of 0.86wt% at 1300 ℃ for 2 hours.The kinetic data for the carbothermal reduction and nitridation of TiO2 by activated carbon or graphite were measured by the proposed method of the continuous all-isothermal thermogravimetric method. And the data were analyzed in terms of weightloss on unit area. Taking activated carbon as reducing agent over the experimental temperature range, the kinetic curves are composed of three stages. In the first stage, the relationship between the weightloss on unit area and time follows the parabolic equation: (△Wt / At)2 = kDt, the total reaction rate is controlled by the diffusion rate of carbon, and the apparent activation energy in this stage is 207.76kJ/mol. In the second stage, the correlation between the weightloss on unit area and time is linear, namely: (△Wt / At)2 =kDt,the total reaction rate is controlled by the oxidation of carbon, and the apparent activation energy in this stage is 204.30kJ/mol. In the third stage, the relationship between the weightloss on unit area and time follows the parabolic equation: (△Wt / At)2 = kDt, the total reaction rate is controlled by the diffusion rate of oxygen or nitrogen, and the apparent activation energy in this stage is 255.69kJ/mol. When taking graphite as reducing agent over the experimental temperature range, the kinetic curves are best described by the diffusion model, and the apparent activation energy for samples containing graphite at 11001350℃ is 312.61kJ/mol.The influence of technique factors on the nitridation reaction was researched in this paper. The results show that: The carbon particle size and the carbon sources are the most important factors for a rapid reaction, but have influence hardly on the appearance of titanium nitride. The carbon content and nit...
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