Synthesis of 3:2 mullite ceramics from silica-enriched filter cake waste via diphasic gels method

Mullite ceramics were synthesized from filter cake waste following the diphasic gel method. Filter cake waste, with over 65% silica content, and aluminum nitrate nonahydrate were utilized as the sources of silica and alumina, respectively. The prepared samples were sintered at various temperatures of 1150, 1250, and 1350 °C. The sintered bodies were then evaluated for porosity, density, compressive strength, and dielectric strength. Differential Thermal Analysis (DTA) revealed exothermic peaks at 970 °C and 1147 °C, corresponding to spinel and mullite formation, which was also confirmed by X-ray diffraction (XRD) analysis. The XRD result also showed single-phase mullite crystallization at 1250 °C. Field Emission-Scanning Electron Microscopy (FESEM) and Energy Dispersive Spectroscopy (EDS) demonstrated morphological changes, grain growth, and uniform elemental distribution in sintered mullite ceramics. The mullite ceramics sintered at 1350 °C exhibited a density of 2.615 g/cm³, compressive strength of 420 MPa, and dielectric strength of 10.2 kV/mm. These findings highlight the potential of the diphasic gel method to produce high-quality mullite ceramics from industrial waste, contributing to cost-effective, eco-friendly materials with promising applications, including electronic devices, electrical power transmission systems, and other structural and functional advanced ceramics.