The mechanical reliability of reversible solid oxide cell (SOC) components is critical for the development of highly efficient, durable, and commercially competitive devices. In particular, the mechanical integrity of the ceramic cell, also known as membrane electrolyte assembly (MEA), is fundamental as its failure would be detrimental to the performance of the whole SOC stack. In the present work, the mechanical robustness of an electrolyte-supported cell was determined via ball-on-3-balls flexural strength measurements. The main focus was to investigate the effect of the manufacturing process (i.e., layer by layer deposition and their co-sintering) on the final strength. To allow this investigation, the electrode layers were screen-printed one by one on the electrolyte support and thus sintered. Strength tests were performed after every layer deposition and the non-symmetrical layout was taken into account during mechanical testing. Obtained experimental data were evaluated with the help of Weibull statistical analysis. A loss of mechanical strength after every layer deposition was usually detected, with the final strength of the cell being significantly smaller than the initial strength of the uncoated electrolyte (σ0 ≈ 800 MPa and σ0 ≈ 1800 MPa, respectively). Fractographic analyses helped to reveal the fracture behavior changes when individual layers were deposited. It was found that the reasons behind the weakening effect can be ascribed to the presence and redistribution of residual stresses, changes in the crack initiation site, porosity of layers, and pre-crack formation in the electrode layers.

SOCs (Solid Oxide Cells) operate in harsh conditions and have to withstand considerable static and cyclic stresses, both mechanical and thermal. Thus, their mechanical stability is threatened. One fundamental aspect is the structural integrity of the cell. In fact, mechanical failure of a single cell can damage the whole stack, reducing the lifetime and the efficiency of the entire system. This study focuses on the ceramic layered structure of an Yttria-stabilized electrolyte supported cell. Its elastic modulus has been measured through destructive and nondestructive techniques (three-point bending test, impulse excitation technique, tensile test). Many literature sources deal with properties of the most common electrolytes and electrodes, yet co-sintering effects and interactions between layers are still not fully comprehended. In this contribution the overall elastic performance of the cell has been investigated, focusing on the role that the interface between layers plays in the changing of resulting mechanical properties. To enable this investigation, layers were added to the electrolyte one by one, thus allowing individual interactions to be distinguished with the help of numerical simulations. Results obtained for consecutive samples through different techniques have been compared and discussed. K E Y W O R D S elastic constants, finite element analysis, fuel cells, layered ceramics

No abstract

No abstract