The crystallization mechanism in high strength glass-ceramics

The addition of NiO to a MgO Al₂ Al₂O₃ SiO₂ basic glass has an influence on the phase separation and crystallization mechanism. The differentiation of the components already detectable in the amorphous state continues in the crystallization process of the nickel-rich glasses. The formation of Ni Al-spinel in the bulk restricts the precipitation of high quartz crystals to the skin. The result is a high strength glass-ceramic with clearly distinguishable bulk and surface regions.     

The coordination of Ni11 in glasses and glass-ceramics of the system MgOAl2O3SiO2

Differences in strength connected with colour variations in NiO-containing Mg-alumosilicate glass ceramics give rise to a remission spectroscopic analysis of the Ni-on. In the base glass, Ni¹¹ occupies tetrahedral and octahedral positions of the dark green NiAl spinel. An increase of the Mg-component and a rise of the melting intensity promote the octahedral nickel coordination and along with it the formation of the strength-reducing, light green Ni-forsterite. The demand for a strong final product is thus met by the technologically desirable shortening of the melting time.