Crystallization kinetics of magnetic glass–ceramics prepared by the processing of waste materials

The objective of the present investigation was to study the feasibility of conversion of an intimate mixture of blast furnace slag and blast furnace flue dust generated by a single industrial company into magnetic glass–ceramic product. Blast furnace slag (BFS) and blast furnace flue dust (BFD) are generated at a rate of 300,000 and 30,000 tons/year, respectively, from iron and steel factory. The crystallization mechanisms of a composition containing BFS and BFD in a 50/50 proportion were investigated by differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The crystallization temperature was found to vary from 900 to 1100 °C and two phases appeared in the crystallized samples: pyroxene Ca(Mg, Fe, Al)(Si, Al)2O6 and magnetite/maghemite. Heating rate and particle sizes effects on crystal growth of powdered samples were studied by DTA. The apparent activation energy of crystal growth using the particle size 180–315 μm was determined to be 355 and 329 kJ/mol for the first and second peak, respectively. The presence of sharp and broad crystallization peaks indicate simultaneous surface and internal crystallization mechanism. Good wear resistance and chemical durability particularly in alkaline environment, combine with good hardness and magnetic properties make this glass–ceramic material potentially useful for various industrial applications.