Base glass nucleation

Over the past 40 years a great deal of research has been done on the nucleation and growth of fibers for industrial uses. The predominant industrial fiber is a silica-based glass. Whiskers, with a high degree of internal structural perfection, have been produced under a variety of special conditions from an extraordinarily wide range of compounds. 

Typical DTA curve of the ZAS base glass is shown in Figure 1. The DTA curve is characterized by some endothermic peak. The endothermic peak is very obvious at 746°C, 824.6°C, 963°C and 1024°C, which indicates there exists transformation of crystal configuration. The endothermic peak is not very obvious at 963°C and 1024 and the endothermic base line shift at 650°C 740°C gives the beginning of glass nucleation temperature zone. 

The Kozuka and Sakka chapter demonstrates how nucleation and polymerization play a role in the formation of silica gels and subsequently silica-based glasses. The section concludes with Healy s chapter, which presents a model of the variations in sihca sol coagulation effected by pH changes and addition of electrolytes. As a final note, a list of references [1-15] is included. 

In principle, any glass can be converted to a glass-ceramic by finding a suitable nucleation agent and the appropriate heat treatment. In practice, a number of technical factors (among which is the production of the base glass) limit the choice. 

Thermal properties and crystallization kinetics of tellurium oxide based glasses. Journal of Ceramic Processing Research, 8, pp. 417-420,1229-9162 Kashchiev, D. (2000). Nucleation, Butterworth Heinemann, ISBN 0750646829, Burlington. 

Appropriate selection of the chemical composition of the base glass, with the usual addition of a nucleating agent... 

James (1982) determined the influence of phase separation on the kinetics of nucleation and crystallization in base glasses. He showed that glasses of the stoichiometric composition of barium disilicate (33.3 mol% BaO, 66.7 mol% Si02) demonstrated the highest nucleation rate compared with other... 

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