Optimal thermal cycle for production of glass–ceramic based on wastes from ferronickel manufacture

Hazardous electro-furnace slag (EFS), dust (D) and converter slag (CS) from ferronickel smelting plant were mixed with glass cullet and vitrified. The optimal heat-treatment regime for transformation of obtained glass into glass–ceramic was evaluated using fast alternative methods: the nucleation step was estimated by DTA analysis, while the crystallization step – by pycnometric measurements. Additional kinetics data, attained by non-isothermal heat-treatments at different heating rates, were also analyzed and the formed crystal phases were studied by XRD analysis. The investigated glass is easily melted (2h at 1400°C) and is characterized by a spontaneous tendency for bulk crystallization. In addition, due to the presence of 1.5wt% Cr2O3 in the batch, supplementary nucleation process takes place, which is a premise for formation of fine crystalline structure and improved mechanical properties. The results elucidate that short heat-treatment at low temperatures (45–60min nucleation at about 650°C and 30–45min crystallization at about 750°C) leads to formation of mono-phase pyroxene glass–ceramic with ~50wt% crystallinity.