Crystallization and microstructural development of nickel-containing aluminosilicate glasses with cordierite stoichiometry

The crystallization behaviour of two glasses with chemical compositions MAl 2O4/SiO2 = 1/2.5, being M=Ni and equimolar mixtures of Mg and Ni, was inves tigated. Glasses were prepared by cooling samples melted at 1650 degreesC. During thermal treatment over the range of temperature up to 1200 degreesC both glasses were first crystallized to form a beta -quartz solid solution, then transformed to alpha -cordierite or spinet depending on the amount of nickel. The temperatures of both the crystallization of beta -quartz solid solution and its further transformation were also dependent on the nominal amount of nickel. Lower temperatures were found for glasses with a large a mount of nickel. UV-Vis diffuse reflectance characterization of the startin g and thermal treated glasses indicated that the Ni+2 cations located in te trahedral sites in the glass moved into octahedral sites after forming the final crystalline phases. The microstructural features of alpha -cordierite -based material from nickel-magnesium cordierite glasses heated at 1100 deg reesC, examined by field emission scanning electron microscopy (FESEM) reve aled the formation of well-defined crystals including regular and elongated hexagonal shaped prisms and square shaped particles. (C) 2001 Elsevier Sci ence B.V. All rights reserved.