Research On The Preparation And Crystallization Behaviors Of Glass-ceramic Glazes

The recycling of blast furnace slag and coal fly ash, two of the largest industrial solid wastes in China, indicates a terrible situation with simple utilization and poor technology. It is urgent to make new products with high added value. This paper aims at finding ways to apply them in the field of modern building materials. The structures and properties of the obtained samples were characterized through DTA, XRD and SEM. Results show that:A composition of 36 w% coal fly ash,24 w% blast furnace slag and 40 w% albite can be designed to prepare glass-ceramic glaze. The obtained anorthite-based glass-ceramic glaze possessed negligible water absorption, a density of 2.39 g·cm-3, a Vickers hardness of 9.6 GPa, a thermal expansion coefficient of 7.6×10-6 K-1 and good adaptation to the fast sintering technology. The typical structure of the anorthite-based glass-ceramic glaze was that a large number of spherical anorthite crystals with a uniform size of about 250 nm distributed well in the vitreous matrix. The anorthite was formed in two approaches- "nucleation-growth" method in the low temperature and "phase separation" method in the high temperature. As the devitrification glass-ceramic glaze revealed a style of surface crystallization, the crystallization activation energy of anorthite was calculated to be 308 kJ·mol-1 by using the Kissinger equation. When adding 1 w% B2O3 into a ceramic support, the anorthite-based glass-ceramic glaze could be applied on it smoothly and tightly, and the glass-ceramic glazed tile had a waste-utilizing rate of 85 w%.Blast furnace slag can be used to prepare white glass-ceramic glaze, with an amount of more than 20 w%. The composition of the white glass-ceramic glaze was chose according to the CaO-Al2O3-SiO2 ternary diagram and the main crystalline phases of the obtained white glass-ceramic glaze were granular anorthite and short-column-shaped wollastonite. Meanwhile, increasing the heating rate and prolonging the crystallization time can both increase the content of anorthite. A certain amount of TiO2 is helpful in controlling the crystallization process and making anorthite as the only crystalline phase. The anorthite crystals were firstly isolated micro-grains, then grew to be strip-shaped, and connected together to form plate-shaped at last. Nucleating agents brought a great influence to the color, phase and structure of the glass-ceramic glaze.The application of glass-ceramic glaze can enhance the appearance of ceramic tiles and improve their properties. Therefore, studies on preparing glass-ceramic glaze derived from industrial solid wastes have important theoretical and realistic significance.