Influence of iron onto the structural reorganization process during the sintering of kaolins

Reference kaolins KGa-1b, KGa-2 and KF are used as starting materials to examine the effect of chemically added iron on their structural transformations (near 950–980 °C) during sintering. The equivalent total Fe2O3 content is varied from 0.21 to 11.72 mass%. Iron addition leads to strong modification of the structural reorganization path of metakaolinite. Iron ions start to diffuse into metakaolinite network at 900 °C and lead to an early breakdown of the system. The corresponding exothermic peak is shifted from 970 °C to 900 °C. Regarding the heating rate, this peak appears to result from three overlapping reactions. The peak temperatures of these reactions are respectively 925 °C, 950 °C and 970 °C. A low heating rate enhances iron diffusion, promoting the structural reorganization process.