TiC及びTiN粉末と高温高圧水との反応

抄録

The reactions between TiC or TiN powder and H₂O have been studied at 200°-650°C under 100MPa. The reaction of TiC with H₂O above 400°C for 3h yielded anatase, CH₄, CO₂ and H₂, and above 500°C rutile was formed additionally. TiN powder with an average grain size of 1.4μm reacted with H₂O above 290°C to yield anatase, NH₃ and H₂, while TiN powder of 9μm reacted H₂O above 480°C and yielded rutile, NH₃ and H₂. The oxidation rate calculated from the weight gain was compared with that from various model kinetic equations. In TiC the rate was best described by the Avrami-Erofeev equation (n=1.3), while the core-shrinking model fitted as well. This suggests that the reaction was controlled by the phase boundary reactions. In TiN the Jander-type model was the best, which suggests that the reaction was controlled by the diffusion through the oxide scale. An Arrhenius plot of the rate constants gave an apparent activation energy of 98kJ/mol. The difference of reaction mechanism between TiC and TiN is attributed to the difference in the gaseous species of reaction products.