Effects of Heat Treatment System on Mechanical Strength and Crystallinity of CaO-MgO- Al2O3-SiO2 Glass-Ceramics Containing Coal Gangue and Iron Ore Tailings

Abstract

For comprehensive utilization of solid wastes, the CaO-MgO-Al2O3-SiO2 glass-ceramics have excellent mechanical properties were prepared the glass-ceramics were prepared with coal gangue and iron ore tailings by a modified melting method. Heat treatment consists of nucleation and crystallization, the best heat treatment in the experiment of coal gangue and iron ore tailings is as followed: nucleation temperature 780 degrees C and crystallization temperature 980 degrees C, the bending strength is up to 283.3 MPa. X-ray diffraction (XRD) shows that crystalline phase is augite, and the mechanical strength of coal-gangue/iron-ore-tailings glass-ceramics becomes higher as the crysallinity increased. While anorthite and diopside become the crystalline phase, the whole strength greatly decreased. Differential scanning calorimetry (DSC) curve and bending strength curves indicate that, the optimum nucleation temperature is 38 degrees C higher than glass transition temperature, meanwhile the best crystallization temperature is 68 degrees C higher that the exothermic one. Scanning electron microscope (SEM) and transmission electron microscopy (TEM) demonstrate that there are two kinds of crystalline phase: one is disordered and arranged closed and other pearl chain-like. Both of arrangements are performed as 200 nm similar to 300 nm grains composed of 40 nm similar to 60 nm submicroscopic particulate, which contributed to the high mechanical strength of coal-gangue/iron-ore-tailings glass-ceramics.