Fly Ash Constituent-Silica and Alumina Role in the Synthesis and Characterization of Cordierite Based Ceramics

Abundant availability of fly ash due to the combustion of coal in thermal power plants presents a major threat to rising environmental pollution. To preserve the environment, fly ash was explored as the starting material for cordierite synthesis. Cordierite ceramics are widely used in the production of microelectronic components, catalyst substrate material for internal combustion engine. Hence, this research was pursued to fabricate the cordierite in a cost effective manner using fly ash containing the major constituent’s silica (SiO₂) and alumina (Al₂O₃). Cordierite synthesis is carried out using raw materials fly ash, magnesia and dopants such as ZrO₂, CeO₂ and TiO₂ at different composition (5–20 wt%). The properties and the microstructure of prepared samples were evaluated using X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG/DTA), and scanning electron microscopy. Their mechanical and thermal properties such as the hardness, the fracture toughness, the flexural strength and the thermal expansion coefficient (CTE) were studied and compared with their morphology. It was found that the hardness, the fracture toughness, and the flexural strength were improved on the addition of the dopant in the cordierite matrix. The cordierite-ZrO₂ ceramics (CZr20) exhibited a Vickers hardness value of 7.04 GPa, the fracture toughness of 3.47 MPa m^½, and flexural strength of 196.72 MPa. The results confirm the cordierite synthesized with fly ash along with dopants is found suitable for use as catalytic substrate materials with improved mechanical properties.