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Citations
... Anode, cathode, electrolyte, and interconnect wires are the basic components of SOFCs [1]. SOFCs have been investigated for such configurations [2,3], materials [4][5][6][7][8], component microstructures [9][10][11][12], electrochemical performance [11][12][13][14], and thermal stresses [14][15][16][17]. A variety of approaches have been chosen to investigate problems related to SOFCs: analytical [3], experimental [4][5][6][7][8][9][10][11][12], and computational [2,[13][14][15][16][17]. Research has shown that electrochemical performance of SOFCs is affected by component microstructure [11,12]. ...
... SOFCs have been investigated for such configurations [2,3], materials [4][5][6][7][8], component microstructures [9][10][11][12], electrochemical performance [11][12][13][14], and thermal stresses [14][15][16][17]. A variety of approaches have been chosen to investigate problems related to SOFCs: analytical [3], experimental [4][5][6][7][8][9][10][11][12], and computational [2,[13][14][15][16][17]. Research has shown that electrochemical performance of SOFCs is affected by component microstructure [11,12]. ...
... 3-D finite element (FE) models of SOFC cathode microstructures are generated from a stack of 2-D microstructure images. Anode (50:50 wt.% NiO:YSZ) and cathode (50:50 wt.% LSM:YSZ) microstructures have previously been analyzed and validated for thermal stress using finite elements by the authors [17]. This study extends the work by investigating the effect of interface degradation under repeated thermal loading on the mechanical integrity and electrochemical performance of SOFC electrodes through finite element simulations. ...
... The tensile mechanical stress buff up to 700 MPa in the new deposited buffer layer was calculated using Stoney's formula considering the initial bending of the SOI substrate [19]: where E Si = 130 GPa is the Young's modulus, Si = 0.278 is the Poisson's ratio [20], t Si = 300 m is the thickness of Si substrate, t buff = 250 nm is the thickness of the grown YSZ/CeO/BTO buffer layers and the expression in brackets considers the curvature radii before (R init ) and after (R final ) growth. The tensile strength of YSZ 200-700 MPa was previously reported based on its composition [21,22]. Further, the mechanical stress in the membrane was investigated step by step after sequential RIE etching of the microbolometer structure from the back side ( Fig. 13): (c) after etching of Si substrate, (d) etching of SiO 2 layer, and finally, (e) etching of Si layer. ...
We report on thermal and mechanical analysis of uncooled antenna-coupled La0.67Sr0.33MnO3 microbolometer made on circular SOI (Silicon On Insulator) membrane with no limitation in its active area (circular membrane with diameter up to 2 500 μm). A simple method how to investigate the thermal conversion efficiency (thermal resistance value - Rth) is introduced. Thermal analysis is supported by the ANSYS modelling and simulation. It is found that Rth and thermal time constant (τ) of our LSMO microbolometer (bolometer sensitivity and time response) can be tuned by the SOI membrane thickness. Rth value as high as 188 K/mW and τ value as low as 0.88 ms are estimated from the thermal simulation for SOI membrane with total thickness of 300 nm (SiO2-200 nm, Si-100 nm). Genesis of the induced mechanical stress changes after main processing steps is found and evaluated to explain the mechanical stability of the LSMO based MEMS microbolometer.
... The effect of temperature-dependent material properties on the probability of failure of the anode is also investigated. The novelties of this work include FE analysis of the behavior of microstructure-based anode models under thermal loads considering temperaturedependent material properties and nonlinear (elastic-plastic) behavior of the nickel phase[22]. ...
Finite element thermal stress analyses of solid oxide fuel cell (SOFC) electrode microstructure models are performed under various conditions to investigate mechanical integrity of electrodes under thermal loads. Image-based three-dimensional finite element models of electrode microstructures are generated from two-dimensional images of actual electrode cross-sections. Finite element thermal stress analyses of anode models under spatially uniform temperature fields of increasing magnitude are performed, and the effects of temperature-dependent material properties and plasticity on mechanical integrity are investigated. Linear elastic material models are found to underestimate the probability of failure of the anode at high temperatures. Analyses of cathode models are performed to study the effects of temperature-dependent material properties and varying phase volume fractions. An approximate heuristic scheme based on boundary pixel modification is developed, validated, and used to derive a microstructure of varying composition from the original microstructure. Limited variations in ceramic phase volume fractions are found to have limited effect on probability of failure of models having temperature-independent material properties, with higher pore volume fraction leading to higher probability of failure. Consideration of temperature-dependent material properties leads to lower probability of failure for the cathode models compared with temperature-independent material properties. Interface degradation under repeated thermal loading is simulated using cohesive elements. Effects of damage on mechanical integrity and electrochemical performance are studied. Three-phase boundary evolution due to mechanical interface damage is evaluated. Three-phase boundary density is found to decrease over a number of heating cycles, indicating that interface damage may be a major mechanism responsible for SOFC performance degradation over time.
Two-dimensional images of solid oxide fuel cell (SOFC) cathode microstructures (50:50 wt.% LSM:YSZ) are used to generate three-dimensional finite element (FE) models. An approximate, heuristic scheme is developed to derive a microstructure of 30:70 wt.% LSM:YSZ composition from the original, real microstructures. The derived model is validated by calculating three-phase boundary (TPB) and phase surface area densities by comparing with data available in the literature. Construction of such derived microstructures will provide insights on the effects of phase compositions on the mechanics of electrode structures. The heuristic scheme is not proposed as a replacement for rigorous approaches such as the random packing model, but rather as a simplified approach for deriving reasonably realistic microstructures of different compositions within a limited range of validity. The models are analyzed using finite elements to estimate thermal stresses and probability of failure using Weibull analysis. The effects of temperature-dependent material properties and phase volume fractions on probability of failure of the cathode are discussed.
