Synthesis and Characterization of Anorthite and Magnetite Glass-Ceramics from Basaltic Rocks

Abstract

Magnetite and anorthite glass-ceramics were prepared from basaltic rocks and ceramic wastes. The effect of the addition of the nucleating agents TiO₂, ZrO₂ and their mixtures on phase assemblages, crystallization and microstructures were investigated. The glasses were melted at temperature around 1450 ^∘C and heat-treated at 900, 1000 and 1100 ^∘C for 2 h the produced glass-ceramics was examined by XRD, thermal expansion coefficient, microhardness indentation, bending strength and SEM. The presence of TiO₂was found to enhance and favor the crystallizability of magnetite formation and retarded the formation of augite after treated at 1000 ^∘C, 2 h, while ZrO₂ and TiO₂ +ZrO₂ mixtures were found to enhance and favor the crystallization of bredigite, anorthite and magnetite formation at the same conditions. TiO₂, ZrO₂ and their mixture favored anorthite formation and retarded augite formation at high temperatures 1100 ^∘C, 2 h. ZrO₂ and ZrO₂ +TiO₂ mixture are much better than TiO₂ in promoting homogeneous nucleation as well as in the growth of extremely fine-grained microstructure of aluminous pyroxene, magnetite, bredigite and anorthite with uniform crystal size that is below 0.3 μm. Mechanical and physical properties, such as microhardness, bending strength, density and thermal expansion coefficient, of the product glass-ceramics have been examined. The results demonstrate that the glass-ceramics have a potential for a wide range purpose, such as building industries.