Study On Glass-ceramics Derived From Waste Slag By A Ceramic-sintering Process

Waste slag based glass-ceramics possess many excellent performances, such as high strength, excellent wear resistance and corrosion resistance, and are widely used in building decoration industry. Currently the manufacture methods of the glass-ceramics commonly are melting method and sintering method. High energy consumption and process complex exist in the early melting process of glass. Blast furnace slag is a glassy material. This indicates that the blast furnace slag can be used as a glass source to make sintered glass-ceramics and vitrifying raw materials at high temperature step can be omitted. This will simplify processes, reduce energy consumption and enhance the utilization of waste residue.This article summarizes the current utilization of blast furnace slag and fly ash and the research of waste slag based glass-ceramics at home and abroad. X-ray fluorescence spectrometer, XRD, DSC-TG, SEM, laser particle size analyzer and other test methods were used for analysis and characterization of raw materials and glass-ceramics obtained. The effects of various parameters on the performance of glass-ceramics, the crystallization kinetics criterion and the coloring effects of several coloring agent were studied.The results show that the phase composition of blast furnace slag and fly ash are vitreous and a small amount of crystalline phase. Glass-ceramics were successfully synthesized using ground blast-furnace slag with fly ash and potash feldspar additives by a conventional ceramic-sintering route. The main phase of obtained glass-ceramics with excellent properties is melilite. With addition of 5 wt% fly ash, glass-ceramics with fine grains (size 2-3μm) which are uniform distribution in the matrix glass have superior performances. A density of 2.66 g/cm3, a high microhardness of 4.9 GPa and a bending strength higher than 96MPa as well as a water absorption lower than 0.12% were obtained. The resistance to chemical corrosion rates close to zero. With the increase of fly ash content, glass-ceramics mechanical performances become deterioration. With a small amount of feldspar flux, the formation of liquid phase at high temperatures can be very good to promote sintering and enhance the densification of glass-ceramics. Glass-ceramics obtained from slag and 5 wt% feldspar flux has a high mirohardness of 5.2 GPa. Fine powders were beneficial to the precipitation of small crystals and the properties of glass ceramics. When crystallization time is 40 min, the prepared glass-ceramics contain fine grains and the shapes of grains were nearly spherical or particle form. When sintering temperature is 1200℃, the prepared glass-ceramics hold the most compact and best performance. Research on crystallization kinetics of this glass showed that K value method is consistent with the experimental results obtained and suitable for crystallization kinetics of this criterion system.The research of effect of Co2O3,Cr2O3,CuO,ZrO2,Fe2O3,MnO2 coloring agents showed that coloring agent content and sintering atmosphere affect the colors of glass-ceramics. The coloring effect of CO2O3, Cr2O3 and MnO2 is clear, glass-ceramic with 1.5 wt% these oxides respectively, appear dark blue, dark green and lavender.