Crystalline mullite formation from mixtures of alumina and a novel material—Silica xerogel converted from sago waste ash

Abstract In this study, we investigate mullite containing ceramics prepared from alumina (α-Al 2 O 3 ) and silica xerogel converted from sago waste ash. The silica xerogel was ground and then mixed with a varying content of α-Al 2 O 3 . The measurements were performed on cylindrical samples sintered at temperatures ranging from 900 °C to 1700 °C. In order to understand the mullitization process and structure formation a series of analyses were carried out using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, thermo-gravimetric analysis (TGA) and a differential scanning calorimetry (DSC). The results show that the mullite phase can be formed at a temperature as low as 1100 °C. It was found that a complete mullitization takes place for the composition of 40 mol% α-Al 2 O 3 sintered at 1600 °C.