MICROSTRUCTURAL CHARACTERIZATION AND PHYSICAL-PROPERTIES OF A SLAG-BASED GLASS-CERAMIC CRYSTALLIZED AT 950-DEGREES-C AND 1100-DEGREES-C

Glass-ceramic materials were developed from Turkish blast-furnace slag s mixed with 3 and 5 wt% titania (TiO2) On the basis of the DTA and th e dilatometry analyses, nucleation experiments were carried out at 725 degrees C and crystallization was performed at 950 and at 1100 degree s C. DTA and X-ray diffraction studies conducted on the glass samples devitrified at 950 degrees C revealed glassy regions and small amounts of gehlenite (Ca2Al2SiO7) and merwinite (Ca3MgSi2O8) phases whereas c omplete transformation to melilite solid solution of akermanite (Ca2Mg Si2O7) and gehlenite phases occurred for those crystallized at 1100 de grees C. Optical microscopy and SEM investigations on the slag glass-c eramic crystallized at 950 degrees C revealed large crystals due to su rface crystallization whereas bulk crystallization was evident for tho se crystallized at 1100 degrees C. For both cases, the crystalline siz e decreased with increasing nucleant content. Wear, hardness, fracture toughness and bending properties of the slag based glass-ceramic mate rial were enhanced with the increase in nucleant content and the cryst allization temperature. (C) 1997 Elsevier Science Limited.