STRUCTURE AND PROPERTIES OF GLASS-CERAMICS FROM BLAST FURNACE SLAG WITH DIFFERENT A l₂O₃/S iO₂ RATIO

Different Al₂O₃/SiO₂ glass-ceramics were prepared from blast furnace slag by sintering method. The structure and properties of glasses or glass-ceramics were investigated by DSC, XRD, SEM, FTIR, 27Al MAS NMR. The DSC results showed that with the increase of Al₂O₃/SiO₂, the glass transition temperature (Tg) first decreased and then increased, reached the minimum when Al₂O₃/SiO₂ was 0.34. The volume density, bending strength and microhardness of glass-ceramics also showed the same variation rule. Structural analysis showed that when the Al₂O₃/SiO₂ increased from 0.19 to 0.34, Q₂ gradually transformed into Q₁ and Q₃; when the Al₂O₃/SiO₂ continued to increase from 0.34 to 0.39, Q₁ and Q₃ decreased while Q₂ increased. The variation of [AlO4] and [AlO6] made the glass network structure the loosest when Al₂O₃/SiO₂ was 0.34. Gehlenite was the main crystalline phase in glass-ceramics, and with the increase of Al₂O₃/SiO₂, the precipitation of gehlenite increased, while the precipitation of diopside and hyalophane decreased.