Utilization of coal-ash minerals for technological ceramics

Glasses synthesized from Utah bituminous coal-ash melts were crystallized to form glass ceramics to determine the feasibility of coal-ash utilization. The use of additives to promote glass formation and catalysts to serve as nucleation sites for crystallization was studied. The microstructure of the crystalline phase was investigated using X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy. The bulk glasses and glass-ceramics were evaluated by Knoop microhardness and density measurements. The crystalline phase formed has been identified as anorthite, CaAl₂Si₂O₈. Crystallization of the ash was possible up to a maximum of approximately 40%. The use of TiO₂ as a nucleation catalyst did little to improve the degree of crystallinity; however, the crystal phase became better defined when this catalyst was used, even in small amounts.