Research On The High Temperature Cycling Properties Of Seals For SOFC

Solid oxide fuel cell is a solid electrochemical device which converts chemical energy efficiently into electric power. SOFC has attracted attention in energy field because of the high energy density, the potential range of fuel sources, non-pollution, and solid state modular assembly. As the key technology in SOFC, sealing is significant for the development of SOFC.Seals design should meet several requirements due to the high operating temperature of SOFC, such as thermal, chemical, sealing and electrical properties. Seals often react with metallic interconnect in SOFC application, which leads to the formation of cracks at the interface because of the high thermal expansion of chromates.This study was to provide systematic and profound information on the sealing glass of SrO-CaO-SiO2-B2O3 system. Firstly, the work about the effect of Al2O3 on borosilicate glass system was carried out. The results show that Al2O3 as network former improves the stability of glass network. The devitrification tendency of glasses decreases with increasing Al2O3 content. The condensed glass structure and increasing residual glass content play opposite roles on the interfacial reaction. In addition, the good bonding can be observed at the interface between Cr-containing interconnect and glass containing 4 mole% Al2O3, held at 700 ℃ for 100 hours.Secondly, the effect of ZrO2 on the structure and chemical compatibility of borosilicate glass system was investigated. The increases in the glass transition temperature and softening temperature of the glasses, with the addition of ZrO2, indicate that the glass structure is condensed by the ZrO2 dopant. The fraction of Cr6+ in the glass/Cr2O3 reaction couple decreases significantly with increasing ZrO2 content at 700℃ because of the condensed glass structure; whereas, the fraction of Cr6+ increases with increasing ZrO2 content at 750 ℃ and 800℃. Good bondage can be observed at the interfaces between glasses containing 4 and 6 mole% ZrO2 and Crofer 22APU after holding at 800 ℃ for 100 hours.Finally, the thermal stability of SrO-CaO-SiO2-B2O3-ZnO system was studied. The results show that the glass transition temperature and the softening temperature decrease with the addition of ZnO. In addition, the greater ZnO content accelerates the weight loss of glasses, indicating a decrease in the thermal stability of glasses.