Reactions between MgAlON-BN Composites and CaO-SiO2-Al2O3-MgO-“FeO” Slag

Abstract

The reactions between MgAlON and MgAlON-BN composites and synthetic CaO-SiO2-Al2O3-MgO-“FeO” slag at different temperatures were investigated under stagnant condition using the ‘‘finger’’ experiment as well as X-ray sessile drop methods. The corrosion rate was denoted by the radius difference between the initial radius of the specimen rod and the unreacted core at definite time intervals. The experimental results showed that the radius difference is linear with the square root of time. This indicated that the diffusion of ions in the slag through the product layer is the rate-determining step. One product layer was observed between the unreacted core and slag. X-ray images showed that gas bubbles were generated during the slag penetration. The slag penetration process depends strongly on the temperature. The apparent activation energy was evaluated to be 376.4 kJ/mol. The FeO addition into slag increased the slag corrosion rate. This is most probably due to the decrease of the slag viscosity, because the Fe+2 generally behaves as a network breaker. Furthermore, MgAlON and boron nitride (BN) can be oxidized by FeO, which also increased the slag corrosion rate. The slag corrosion rate decreased with increasing BN content. This can be explained by the fact that the grain boundary interfacial energy decreases with the increase of BN content and nonwetting of BN by molten slag compared to pure MgAlON.