Glass - Back to the Future!

Presenting Author:
Yudai Katagami

article posted 6 April 2016

Yudai Katagami works for NEG and is a member of ICG TC14 Gases in Glasses.

Identification of bubble generation potential of glass melts with low DC and AC voltage by direct observation

Y. Katagami*1, Y. Kii1, N. Yoshida1, M. Kawaguchi1, A. Yamada2, S. Yoshida2, J. Matsuoka2 & Y. Miura2
1 Nippon Electric Glass Co., Ltd, 7-1,Seiran 2-Chome, Otsu, Shiga 520-8639, Japan
2The University of Shiga Prefecture, 2500, Hassaka, Hikone, Shiga 522-8533, Japan

Bubble in glass products is a major defect. There are some causes of the bubble and electrochemical reaction is one of them. An understanding of bubble formation resulting from electrochemical reaction requires the bubble generation potential in molten glasses. In an attempt to identify the bubble generation potential, DC voltage was applied between Pt electrodes in soda-lime silicate (SLS) melts with different fining agents (SO3, SnO2, Sb2O5) in a transparent silica crucible and bubble generation on the electrodes was confirmed with high-temperature observation (HTO) system. Oxygen bubble generation potential by three-electrode method at the anode was around +010 V at 1300C (Figure 1(a)) irrespective of the type of fining agent added. It was found that the SO2 bubble generation potential by three-electrode method at the cathode in the SLS melt with SO3 was around -030 V (Figure 1(b)). As for two-electrode method, voltage drop between electrodes could affect bubble generation potential. However the voltage drop in this measurement system was estimated up to 0002 V, and there was little difference of bubble generation potentials in the SLS melts between three-electrode and two-electrode method. The effect of AC voltage and glass composition on bubble generation potential will be also discussed.

Figure 1. HTO images of platinum electrode before and after electrolysis test at 1300C on SLS with SO3 (a) at the anode by three-electrode method, (b) at the cathode by three electrode method and (c) by two-electrode method