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
) 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 +0·10 V at 1300°C (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 -0·30 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 0·002 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 1300°C 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