Abstract
(1) In order to control the concentration of nucleation agents in the melt of the domestic scoria, 1-2wt% sucrose were added. When the ratio of FeO/Fe2O3 ranges between 0.93 and 1.32, the optimum crystallization was obtained with the crystal size of about 0.1μm and the homogeneous microstructure.
(2) The impurities, FeO, Fe2O3, and TiO2 affect the formation of magnetite and ulvospinel which are the nucleation agent of the all specimens in this study. Not only the FeO/Fe2O3 ratio but also the absolute amount of iron oxides are important factors in the nucleation process. When 1-2wt% sucrose were added, the ratio of FeO/Fe2O3 increased from 0.18 to 0.93-1.32.
(3) The temperature and holding time for the nucleation and crystallization as well as the activation energy for crystallization were determined by DTA. The nucleation temperature varied from 625° to 760°C and that for crystallization from 800° to 850°C depending on the amounts of additives.
(4) The crystalline phases after the heat treatment were diopside, alkermanite, and gehlenite as a major phases and also α-quartz, spinel and grossular were found as the minor phases.
(5) The scoria glass with the addition of 20wt% SiO2, 7wt% CaO, 5wt% MgO, and 1wt% sucrose shows the lowest activation energy and also developes fine and uniform crystal particles.
(6) The thermal expansion coefficients of the glass-ceramics are higher than those of parent glasses.
