窒素雰囲気下におけるSi_3N_4とCrとの反応の速度論

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The kinetics and the mechanism of reaction of Si_3N_4 with Cr have been investigated in an atmosphere of N_2. Using powder mixtures of Si_3N_4 and Cr, the reaction rates were measured by means of a thermobalance at temperatures from 773 K to 1573 K, and reaction products were examined by X-ray diffraction. Below 1423 K, N_2 gas reacted with Cr particles to produce Cr_2N and CrN. Above 1473 K, Cr nitrides were produced at the initial stage of the reaction, and a CrSi solid solution and Cr_3Si were formed on the nitride layer at the late stage. The initial reaction followed the linear rate law. Below 923 K, the activation energy was 35 kJ/mol and the rate-determining step was the diffusion of N_2 to the surface of the Cr particles. Above 973 K, the activation energy was 202 kJ/mol and the rate was probably mixed-controlled by the gaseous diffusion and the interfacial reaction. When the Cr particles were covered with the reaction products, the kinetics was described by the parabolic rate law. The activation energies were 148 kJ/mol below 1273 K and 305 kJ/mol above 1323 K. The solid state diffusion through the reaction layer may be considered as the rate-determining step.
社団法人日本セラミックス協会の論文
1993-06-01