Journal of Power Sources 205 (2012) 307–317 Contents lists available at SciVerse ScienceDirect Journal of Power Sources jo ur nal homep age: www.elsevier.com/locate/jpowsour Joint strength of a solid oxide fuel cell glass–ceramic sealant with metallic interconnect Chih-Kuang Lin a,∗ , Jun-Yu Chen a , Jie-Wun Tian a , Lieh-Kwang Chiang b , Si-Han Wu b a Department of Mechanical Engineering, National Central University, Jhong-Li 32001, Taiwan b Nuclear Fuel & Material Division, Institute of Nuclear Energy Research, Lung-Tan 32546, Taiwan a r t i c l e i n f o Article history: Received 27 October 2011 Received in revised form 20 December 2011 Accepted 1 January 2012 Available online 10 January 2012 Keywords: Planar solid oxide fuel cell Glass–ceramic sealant Metallic interconnect Joint strength Pre-oxidation treatment Thermal aging a b s t r a c t The aim of this study is to investigate the joint strength between a newly developed glass–ceramic sealant (GC-9) and metallic interconnect (Crofer 22 H) for planar solid oxide fuel cells (pSOFCs). The joint strength is evaluated at room temperature and 800 ◦ C under shear and tensile loading using two types of sandwich specimen. Effects of number of initial sealant-spreading side, pre-oxidation of metallic interconnect, and thermal aging in air on the joint strength are studied. Regardless of testing temperature and loading mode, the joint strength of specimens initially with two sides of glass–ceramic sealant is greater than that of single-sided ones. A pre-oxidation treatment of the metal coupon at 900 ◦ C for 2 h or 20 h does not generate a beneficial effect on the shear and tensile joint strength for all the given testing conditions. Compared to the shear strength of unaged joint specimens, a reduction of 17–19% in shear joint strength at 800 ◦ C is observed for variously aged ones. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Solid oxide fuel cells (SOFCs) have the highest efficiencies among the fuel cells developed as they utilize solid ceramics as the elec- trolyte and electrode and operate at high temperatures. In recent development of SOFCs, planar SOFCs (pSOFCs) have attracted more attention as they are easier to fabricate, operate at a lower tem- perature (below 800 ◦ C), and offer a higher power density over the tubular ones. In practical applications of pSOFCs, unit cells are inte- grated by bipolar interconnects into a multi-cell stack to generate a high voltage and power. Therefore, interconnects play a very impor- tant role in structural and electrical connection of unit cells. During the stacking process and operation, hermetic sealants are needed to maintain gas tight between components in SOFCs. Sealants for SOFCs must have necessary adherence, mechanical integrity, chem- ical stability and compatibility, electric insulation, and thermal expansion match at operating temperature. The high-temperature operation, however, gives rise to significant thermal stresses due to mismatch of coefficient of thermal expansion (CTE) between components and temperature gradients in the SOFC system [1,2]. When a rigid type of sealing is applied to pSOFCs, joining glass–ceramic sealants to metallic interconnects is very common. During cyclic operation of pSOFCs, generation of thermal stresses ∗ Corresponding author. Tel.: +886 3 426 7340; fax: +886 3 425 4501. E-mail address: t330014@cc.ncu.edu.tw (C.-K. Lin). is inevitable leading the seals to be subjected to tensile and shear stresses [1,2]. Once the stresses exceed the corresponding strength of the joint between a glass–ceramic sealant and metallic intercon- nect, failure of the sealing may lead to gas leakage and degradation of cell performance. For this reason, it is necessary to investigate the mechanical properties of such a joint for assessing the struc- tural reliability of a pSOFC stack. The mechanical properties of a joint do not belong to that of a single material while they are inter- facial properties between two materials. Any interaction between the glass–ceramic and metal may influence the mechanical prop- erties of the joint. Although many studies, e.g. [3–9], have recently investigated the bonding and chemical interaction of glass–ceramic sealants with metallic interconnects, little literature is related to the mechanical properties of such joints in pSOFCs. Only a limited number of studies [10–13] have been focused on this subject which is important to advance the development of SOFC technologies. In the study of Smeacetto et al. [10], bonding strength between a glass–ceramic sealant (SiO 2 –Al 2 O 3 –CaO–Na 2 O, SACN) and two Cr- containing metallic interconnects (Crofer 22 APU and AISI 430) was evaluated under tensile loading at room temperature, but no quan- titative data of mechanical strength were reported. It was found that fracture of the Crofer 22 APU/SACN/Crofer 22 APU joint speci- mens always occurred within the glass–ceramic layer and never at the interfaces in the joint [10]. In order to obtain a good adhesion between the AISI 430 steel and SACN glass–ceramic, a pre-oxidation treatment of the metal is essential [10]. Chou et al. [11,12] inves- tigated the tensile joint strength of a (SrO,CaO)–Y 2 O 3 –B 2 O 3 –SiO 2 0378-7753/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.jpowsour.2012.01.048