Glaze Surface Tension Effects on Bubble Evolution

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Alfred University. Faculty of Ceramic Engineering. Kazuo Inamori School of Engineering
The objective of this work was to investigate the glaze surface tension effect on bubble evolution during firing, and the relationship between glaze surface tension, melt viscosity and bubble evolution. A sessile drop technique was used to measure to glaze surface tension. Viscosity temperature reference points at the glass transition temperature (Tg), dilatometeric softening temperature (Td), and side-view hot-stage microscope halfsphere temperature where is assumed to be 103.55 Pa•s, were used in VFT equation to estimate viscosity values. Bubble evolution during firing was studied with the top view hot-stage microscope. The influence of additives (MoO_{3} and Sb_{2}O_{3}), frit composition (RO:R_{2}O), and substrate composition (alumina, porcelain, and porcelain-glass) were studied for lead containing and leadless glaze systems. It was shown that 0.5mol% addition of MoO_{3} had a significant effect on bubble formation and bursting. Addition of 0.1-0.2 mol% Sb_{2}O_{3} tended to increase the number of large bubbles in glazes studied. The study showed lowering viscous resistance is more important to affect bubble evolution than decreasing surface tension. However, the surface tension played a major role in controlling the initial closing of pores and bubble formation during firing, which significantly reduced the bubble evolved in the firing. Two statistical models were developed to predict the relationships of surface tensionviscosity- bubble. The model predict that that lowering surface tension is beneficial for bubble removal, however, the bubble volume tends to decrease with the continuing increase of surface tension. Also, the reaction at the glaze-substrate interface facilitates the bubble nucleation and residing at the interface.
Tension, Surfaces, Glazes, Bubbles, Ceramics