Network structure and thermal stability study of high temperature seal glass

Abstract

Articles you may be interested inSynthesis and structural studies of multi-component strontium zinc silicate glass-ceramics AIP Conf. Proc. 1512, 568 (2013) High temperature seal glass has stringent requirement on glass thermal stability, which is dictated by glass network structures. In this study, a SrO-La 2 O 3 -Al 2 O 3 -B 2 O 3 -SiO 2 based glass system was studied using nuclear magnetic resonance, Raman spectroscopy, and x-ray diffraction for solid oxide cell application purpose. Glass structural unit neighboring environment and local ordering were evaluated. Glass network connectivity as well as silicon and boron glass former coordination were calculated for different B 2 O 3 : SiO 2 ratios. Thermal stability of the borosilicate glasses was studied after thermal treatment at 850°C. The study shows that high B 2 O 3 content induces BO 4 and SiO 4 structural unit ordering, increases glass localized inhomogeneity, decreases glass network connectivity, and causes devitrification. Glass modifiers interact with either silicon-or boron-containing structural units and form different devitrified phases at different B 2 O 3 : SiO 2 ratios. B 2 O 3 -free glass shows the best thermal stability among the studied compositions, remaining stable after thermal treatment for 200 h at 850°C.

Tuning the thermal properties of borosilicate glass ceramic seals for solid oxide fuel cells

“…1). The decrease in T c of glasses with increasing B 2 O 3 content is in agreement with the previous results in SrO-La 2 O 3 -Al 2 O 3 -B 2 O 3 -SiO 2 based glass system, 22 in which the addition of B 2 O 3 was found to induce BO 4 and SiO 4 structural unit ordering, increase glass localized inhomogeneity, decrease glass network connectivity, and cause devitrification. The coefficient of thermal expansion (CTE) of quenched glasses ranges 11.2-11.7 × 10 −6 K −1 ; whereas, the CTE of heat-treated samples, decreases from 9.5 to 7.5 × 10 −6 K −1 , with increasing borate content.…”

Seal glass for solid oxide fuel cells

“…2 for borosilicate glasses [27,28,32,43]. The reasons are as follows [27,44]. First, both three-coordinated BO 3 and fourcoordinated BO 4 structural units are present.…”

“…First, the degree of network connectivity decreases with increased fraction of non-bridging oxygen-containing structural units. Second, coexistence of several different types of structural units induces heterogeneity in a glass network structure [16,44,[69][70][71][72][73][74]. Silicate glasses have a higher degree of devitrification resistance than borate and borosilicate glasses because of their higher glass network connectivity, as demonstrated in Fig.…”

“…The origins of devitrification are the very small nuclei formed during glass making, heterogeneity in glass network structure, surface flaws, and residual stress from mechanical polishing [18,21,27,33,44,67,68]. Devitrification resistance depends on seal glass composition.…”

Sealing Evaluation of an Alkaline Earth Silicate Glass for Solid Oxide Fuel/Electrolyser Cells

“…The glass is also stable for at least 1,000 h at 800°C in oxidising and H 2 /H 2 O reducing atmospheres. No bulk devitrification or weight loss is observed [14,15]. The glass transition temperature (T g ) and the dilatometric softening point (T d ) are 775 and 815°C, respectively [16,17].…”