Structural Characterization of Mullite-Based Ceramic Material from Al2O3 and Silica Xerogel Converted from Sago Waste Ash

In this investigation, mullite ceramics were produced by mixing Al2O3 and amorphous silica xerogel (SX) extracted from sago waste ash. The composition was prepared by adding an amount from 0 to 80 mol% of Al2O3 into SX. The samples were dry pressed and sintered in the temperature range between 900°C and 1200°C. Their properties have been characterized on the basis of the experimental data obtained using thermal analysis (DSC/TGA, X-ray diffraction and scanning electron microscopy (SEM). The results show that two major differences become obvious when comparing the samples loaded by the smaller and larger amount of Al2O3. First, cristobalite formation is retarded in the sample loaded by the larger amount of Al2O3. Second, at 1200°C, the observed volume fraction of mullite is higher in the sample loaded by the larger amount of Al2O3. The DSC analysis indicates that the mullite crystallization takes place at 1200°C for 60 mol% Al2O3 loaded SX sample as confirmed by the XRD pattern. It was found that there was not a complete reaction of mulitization for sample sintered up to 1200°C.