ИСТИНА

During the fabrication of N-SiC sidewall lining the reaction between Silicon and gaseous Nitrogen resulting bonding Silicon Nitride, starts beginning from 1100оС. Nitrogen may react with solid Silicon, molten Silicon and with vapors of Silicon. The reaction of Nitrogen and Silicon is strongly exothermic. On the final stages of N-SiC formation the temperature of the process is higher, than the melting point of Silicon. Some part of Silicon is in the gaseous phase. The difference between the temperature in the middle of the shapes and at near the edges might be critical for the gradients of porosity and density in refractory shapes. Volatile Silicon tends to move in the places with lower temperature. Usually the gradients of porosity in the center of shapes and at the edges are 1-2 %, but sometimes it may reach 5-7%. Usually the problems with side lining in Aluminium reduction cells are due to the design of the pots or due to the problems with reduction technology (overheating, etc.), however that may have connection with the structure of N-SiC refractories.