Thermodynamic and kinetic investigation of high-temperature interactions between float glass and tin

The primary goal of this research was to understand the role of iron and sulfur in glass on tin penetration during the float process, and to describe the factors controlling glass/tin interdiffusion reaction(s). Tin penetration increased with increasing iron concentration, and with increasing sulfur concentration at fixed iron levels. The tin depth profile in the high-iron glasses, in general, exhibited a 'bump' at approximately half the penetration depth which was correlated with the depletion depth of iron and sulfur.; A miniature float bath apparatus was used to systematically investigate the effects of time, temperature, glass composition and redox, and tin bath chemistry on the nature of tin penetration during the float process. Tin depth profiles similar to those measured in commercial float glass were reproduced in the lab-scale float apparatus. As temperature increased, the tin concentration in the outer 1{dollar}mu{dollar}m decreased, yet accumulation at greater depths (2-120{dollar}mu{dollar}m) occurred. Increasing the iron concentration in the tin bath reduced the overall tin penetration and iron depletion in the high iron glasses at higher temperatures. At lower temperatures, the effect of iron doping in the tin was less noticeable. Iron penetration from the tin bath into the low iron glasses was observed at lower temperatures. High levels of oxygen in the tin bath resulted in higher tin penetration, but the penetration depth was not effected.; The thermodynamic calculations of high temperature phase equilibria revealed that regardless of the glass composition or iron redox, an oxygen activity differential existed between the glass and tin bath which spanned up to 15 orders of magnitude. This oxygen activity gradient was fundamental to the formation of the bump observed in the tin penetration profiles of glasses floated on the lab tin bath. A simple diffusion model was created to generate tin penetration profiles which were similar to the glass profiles. Assuming the oxygen activity gradient followed the iron depletion profiles in the glasses, the formation of the bump in the tin penetration profiles was found to be the result of an accumulation of Sn{dollar}sp{lcub}4+{rcub}{dollar} at the point of tin oxidation.