Creep Behavior of Glass/Ceramic Sealant and its Effect on Long-Term Performance of Solid Oxide Fuel Cells

Abstract

The creep behavior of glass or glass–ceramic sealant materials used in solid oxide fuel cells (SOFCs) becomes relevant under SOFC operating temperatures. In this paper, the creep of glass–ceramic sealants was experimentally examined, and a standard linear solid model was applied to capture the creep behavior of glass–ceramic sealant materials developed for planar SOFCs at high temperatures. The parameters of this model were determined based on the creep test results. Furthermore, the creep model was incorporated into finite‐element software programs SOFC‐MP and Mentat‐FC developed at Pacific Northwest National Laboratory for multiphysics simulation of SOFCs. The effect of creep of glass–ceramic sealant materials on the long‐term performance of SOFC stacks was investigated by studying the stability of the flow channels and the stress redistribution in the glass seal and on the various interfaces of the glass seal with other layers. Finite‐element analyses were performed to quantify the stresses in various parts. The stresses in glass seals were released because of creep behavior during operations.

A continuum thermo-inelastic model for damage and healing in self-healing glass materials

“…However, its further implementation in the SOFC stack has been overshadowed by the intrinsic vulnerability of conventional glass seals to brittle fracture upon thermal cycling during which tensile stresses develop as a result of the mismatch of thermal expansion coefficients of different stack components (Liu et al, 2010). The newly invented thermally responsive self-healing glass that automatically restores its mechanical integrity at high temperatures is encouraging to many, however, lack of fundamental understanding and predictive capability over its long term mechanical functionality and stability at the extreme cell operating temperatures still pose tremendous challenges to the wider applications of this straightforward engineering concept (Liu et al, 2011b;Mihans et al, 2011). In particular, a quantitative and mechanism-based description of its essential stress and temperature dependent degradation and recovery kinetics remains to be sought-after.…”

Review on silicate and borosilicate‐based glass sealants and their interaction with components of solid oxide fuel cell

“…33 Also, the creep behavior of glass-ceramic reduces the height of fuel flow channels. 32 During SOFC operation, glass sealants interact with other components of SOFC and form some detrimental and unavoidable crystalline phases. The change in the volume fraction of these phases and their chemical nature, a phase transition to temperature, and pressure variation usually reduce the thermal and mechanical stability of glass sealants, which leads to a decrease in efficiency and lifetime of the device.…”

“…30 The creep behavior of glass sealants/interconnect has been reported at high temperature by many researchers. [31][32][33] Normally, creep cracks initiate at the interfaces and fast fracture takes place within the glass-ceramic sealant. 33 Also, the creep behavior of glass-ceramic reduces the height of fuel flow channels.…”

Advanced analysis of flexural test results of sealant for solid oxide cells

“…The plastic strains of Inconel X‐750 were ignored because the magnitude of stresses was lower than its yield stress. Since data on the viscoelastic behavior of glass–ceramic G were not available, it is assumed that it relaxes like other glass–ceramic sealing material 25 at higher temperatures. For this purpose, the constants of the first two terms of the Prony series are obtained by curve fitting of the experimental data (Figure 3).…”