Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft
Doi
Abstract
Glass-ceramics in the system diopside-anorthite-orthoclase were prepared using the waste known as the by-pass cement dust in the amount of 36 % of the batch constituents. The effects of addition of the nucleating agents Cr2O3, LiF, and mixtures of them on the crystallizability, phase assemblages, and the resultant microstructures were investigated. Low concentration of Cr2O3 (0.5 wt%) causes volume crystallization and formation of fine-grained microstructures of microcline, anorthite and aluminous pyroxene. Higher concentrations of Cr2O3 favor formation of leucite and aluminous pyroxene and inhibit crystallization of anorthite. LiF causes the formation of microcline and its transformation into orthoclase. It also increases the crystallizability with the formation of nonuniform coarse-grained texture. Α mixture of 0.5 % Cr2O3 and 1.5 % LiF causes a synergistic effect, where fine-grained microstructure is formed (due to Cr2O3) with orthoclase formation (due to LiF) in addition to aluminous pyroxene and anorthite. The effects of various Cr2O3 concentrations were discussed on the bases of the increased viscosity and separation of Cr2O3 and/or chromiumspinel phases. The effects of LiF were attributed to the role of fluorine ions in reducing the viscosity of the glasses, consequently facilitating crystallization of the structurally more complex silicate in addition to favoring reaching thermodynamic equilibrium
