Si₃N₄粉とCr粉の高温反応機構

抄録

The kinetics and the mechanism of the reaction of Si₃N₄ with Cr have been investigated. Using powdered Si₃N₄-Cr mixture, the reaction rate was determined by means of a thermo-balance in an Ar gas stream at temperatures from 1273 to 1573 K. The reaction products were examined by X-ray diffraction.
The reaction of Si₃N₄ with Cr took place after heating to about 1250 K. Cr₂N and Cr₃Si were produced below 1373 K. Above 1473 K, Cr₂N disappeared and Cr₃Si changed to CrSi via Cr₅Si₃. The initial rate was described by the linear rate law. The activation energy was 260 kJ/mol. A chemical process may be considered as the rate-determining step. When the Cr particles were covered with the reaction product layer, the kinetics obeyed the parabolic rate law. The activation energy was 365 kJ/mol. The reaction rate is probably controlled by the diffusion through the reaction layer.