Resistance of silicon carbide refractories to the action of carbon monoxide, alkalis, and slag

Conclusions

The effect of alkalis, slag, and carbon monoxide on silicon carbide and nitride was studied at elevated temperatures up to 1550°C. It was established that silicon carbide is destructed most rapidly at 1200°C under the action of the investigated factors. The properties of silicon nitride virtually do not change on heating up to 1400°C in the presence of carbon monoxide; one observes a slight decrease in the nitrogen content of the system only at 1550°C and an increase in the silicon content in the 1200–1550°C range due to the dissociation of Si₃N₄ and the formation of Si₂ON₂.

At 1200 °C, carbon monoxide and alkalis significantly influence the property variation of the silicon carbide refractories containing a silicon nitride-based binder only during the first 2 h of holding; this is confirmed by the abrupt decrease of the open porosity and the apparent density during this period. Further increase in the holding period up to 16 h does not have a significant effect on the variation of the properties of the products owing to the protective glassy coating formed on the refractory surface as a result of partial oxidation of SiC. Our studies confirmed that the silicon carbide refractories containing a silicon nitride binder possess a high degree of stability under aggressive conditions.