Ceramics-Silikáty 46 (1) 15-23 (2002)

THE EFFECT OF NUCLEATION CATALYSTS ON CRYSTALLIZATION CHARACTERISTICS OF ALUMINOSILICATE GLASSES 

Samia N. Salama, Saad M. Salman, Hussein Darwish

The effects of compositional variation, nucleation catalyst and thermal treatment on the nature, type and stability field of crystallizing phases and microstructure formed in CaO and/or MgO aluminosilicate glasses are described using differential thermal analysis (DTA), X-ray powder diffractometry (XRD) and scanning electron microscopy (SEM). Wollastonite solid solution was formed in calcium aluminosilicate glass-ceramics, however, with MgO replacing CaO, pyroxene solid solution was developed. The addition of the nucleants brings varieties of aluminosilicate phases e.g., plagioclase, melilite and spodumene developed together with fluorite, fluorosilicate and/or TiO₂-bearing phases. Intense uniform bulk crystallization with fine-grained microstructure was achieved by an addition of TiO₂ or CaF₂ rather than LiF. The role of the nucleating agents during the formation of the crystal phases and the microstructure of the resultant glass-ceramics are discussed.

Keywords: Crystallization, Aluminosilicate glasses