Glass-ceramic production from magnesite waste and investigating of their properties

In this study, the magnesite waste is used for MgO-Al2O3-SiO2 (MAS) glass-ceramics production, economically. The effects of heat treatment temperature on crystallization behavior and precipitated phases in the produced glass-ceramics are investigated. Crystallization behavior of glasses in the presence of Li2O as a nucleation agent was studied. As raw materials, 20%wt. quartz, 35% magnezite waste, 25% kaolinite, 20% alumina and excess 2.5% Li2O are mixed according to cordierite chemical formula (2MgO.2Al2O3.5SiO2). Mixing process is carried out for 2 h using zirconia balls in the distilled water media and then prepared mixture is dried at 110°C for 24 h. The powder mixture is melted in an alumina crucible at 1500oC for 2 h. The glasses are casted into a graphite mould, and then an annealing process is carried out at 600oC for 1 h to remove thermal residual stresses. Produced glasses are applied to differential thermal analysis (DTA) and thermo gravimetric analysis (TGA) to detect the crystallization temperatures. The samples are heated for the glass-ceramic transformation at 1000oC, 1050oC, 1100oC, 1150oC and 1200° for 1,3,5 and 10 h. Produced samples are characterized by X-ray diffractometer (XRD) and scanning electron microscopy (SEM-EDS). Because glass powder sintering proceeds by viscous flow, the decreasing glass viscosity shows good effect on its sinterability. In order to fabricate dense glass-ceramics, it may be a critical factor to select adequate glass composition and flux, which reduces glass viscosity. Many researchers have reported the effects of nucleating agent and heat treatments, such as TiO2, NiO, ZrO2, MgF2, CeO2 and ZnO, on the crystallization of MgO-Al2O3-SiO2 glass. However, the effect of Li2O on crystallization behavior hasn't been researched in detail. The main goal of this study is to analysis the effects of Li2O of the MAS system, which hasn't been studied before, and preparing several compositions using the most efficient nucleating agent TiO2 for produce MgO-Al2O3-SiO2 glass ceramics from the industrial waste economically (low temperature, low time, low raw material cost). Keywords: MAS glass-ceramics; Magnesite waste;