Effects of TiO₂ on the microstructure transformation of glass ceramics prepared by fly ash and quartz sand

Glass ceramics were prepared by fly ash and quartz sand, and subsequently heat treated with different processes. The glass ceramic specimens with different ingredients after heat treatment were investigated. When the mass fraction of ash fly is 30%, transitional phase Ca₂SiO₄ precipitates at first in the specimens without TiO₂ during heating at 780℃, then it dissolves and disappears during crystallization at elevated temperatures, and finally the stable equilibrium phase of anorthite precipitates. When the mass fraction of TiO₂ increases from 0 to 15%, the precipitates change from fusiform Ca₂SiO₄ microcrystals to granular anorthite microcrystals. When the mass fraction of fly ash increases to 40% and that of TiO₂ is 3.5%, a reticular structure appears, and then it will vanish when the nucleation agent of TiO₂ is added to 5%. It can be concluded that the precipitation of the reticular structure is restrained by TiO₂.