Mullite fabrication from natural kaolin and aluminium slag

The structural transformations of kaolin-aluminium slag mixtures during heating were studied using differential thermal analysis (DTA), thermal gravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). The amount of formed mullite increases with the firing temperature. At 1500 degrees C, the mullitization of the mixture is almost complete. The morphology of the formed mullite is bimodal (primary and secondary phases). The primary mullite, formed from processing of kaolin by the gradual collapse of metakaolin from 990 degrees C, has a shape of elongated crystals. The other hand, the secondary mullite formed by solution-precipitation from the glass phase in the presence of alumina particles has a shape of acicular grains. (C) 2018 SECV. Published by Elsevier Espana, S.L.U.