Nano-crystal glass-ceramics obtained by crystallization of vitrified coal fly ash

Glass has been obtained by melting coal fly ash from a power plant in North China with Na2O+CaO and BaO+CaO as fluxing additives. A thermal treatment was employed to convert the obtained glass to nano-crystal glass-ceramics. X-ray diffraction patterns show that the main crystalline phase in both the glass-ceramics is wollastonite (CaSiO3). The crystals are homogeneously dispersed within the parent glass. The average crystal size is below 300 nm, and varies according to heat treatment process used. Physical and mechanical properties, such as density, thermal expansion coefficient, hardness, and bending strength, of the two glasses have been examined and the corresponding microstructures are discussed. The results demonstrate that both glass-ceramics have potential for a wide range of construction application.