Development of barium boron aluminosilicate glass sealants using a sol–gel route for solid oxide fuel cell applications

Abstract

Development of barium boron aluminosilicate glass sealants using a sol-gel route for solid oxide fuel cell applications. (2016) Journal of Materials Science, 51 (2). 979-988.

Optimization of the synthesis route of a barium boron aluminosilicate sealing glass for SOFC applications

“…Four glass-ceramic sealants, with a T g between 596 and 626 °C, showed adequate electrical insulation after a sealing procedure and stable CTE and microstructure after sealing and ageing operation (800 °C-100 h) in air atmosphere. Furthermore, any reaction product at the steel interconnector-glass interface was observed and no hexacelsian or monocelsian crystals were identified in the formed glass-ceramic seals [24]. However, only the CM2 glass (chemical composition: 36%BaO-2.6%Al 2 O 3 -10.3%B 2 O 3 -10.3%MgO-10.3% CaO-30.7%SiO 2 ) allowed preserving the gas-tightness of steel-glasssteel assemblies thermally treated at 700 °C or at 800 °C during 1000 h in air and in H 2 /H 2 O atmospheres [25,26].…”

“…However, promising performances had been obtained on short-term or on mid-term operations in air (up to 1500 h in dual atmosphere with no delamination [19]), in dual atmosphere (no delamination after 750 h [20]) or in real testing conditions with thermal cycles for SOFC applications [21]. In our previous works, we had developed a new sol-gel route to synthesize barium (boron) aluminosilicate glass sealants in order to process these glasses at a lower temperature than using a solid-state route and to improve the performance of these glasses for SOFC applications [22][23][24][25][26]. Indeed, many studies showed that the use of gel mixture could decrease the temperature of glass formation until 200 K below (possibly more) those required when using conventional batch material [27][28][29].…”

“…At 1300 °C, barium aluminosilicate glasses still contained crystals. With the adding of B 2 O 3 , MgO and/or CaO, amorphous and homogeneous BBXAS (BaO-B 2 O 3 -Al 2 O 3 -SiO 2 with X=CaO and/or MgO) glasses were obtained at the same temperature [22][23][24]. Four glass-ceramic sealants, with a T g between 596 and 626 °C, showed adequate electrical insulation after a sealing procedure and stable CTE and microstructure after sealing and ageing operation (800 °C-100 h) in air atmosphere.…”

“…All the glasses were ground using a planetary mill (agate balls and cup) at 400 rpm to obtain powders. Same grinding duration was used in order to obtain similar grain size except for SG1 glass (Table 1), which was already characterized in previous works [24,26].…”

“…4 glasses with the same theoretical chemical composition of the promising CM2 material were prepared (Table 1). 3 glasses were synthesized using the sol-gel route previously described with a final processing heat treatment at 1300 °C during 3 h for SG1 and SG2 glasses and at 1100 °C during 1 h for SG3 glass [23,24]. Concerning the glass prepared by solid-state process, nearly-pure commercial powders BaCO 3 , SiO 2 , MgO, CaO and B 2 O 3 (325 mesh, purity > 99,5%) were mixed together and heated at 1300 °C during 3 h. In this case, BaCO 3 powder was preferred to BaO powder to avoid any influence of residual impurities contained into BaO powders on the final glass chemical 1100°C or 1000°C showed that crystals were present in the formed glass leading to inhomogeneous systems.…”