Stress analysis of solid oxide fuel cell anode microstructure reconstructed from focused ion beam tomography

Clague, Ralph; Shearing, Paul R.; Lee, Peter; Zhang, Z.; Brett, Dan J. L.; Marquis, A. J.; Brandon, Nigel P.

doi:10.1016/j.jpowsour.2010.12.097

Cited by 38 publications

(32 citation statements)

References 16 publications

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“…38 The microscopic implications of thermal expansion mismatch between single parties, have been explored elsewhere. 19,20 Moreover, as discussed previously, the agglomeration effects observed here during operational cycling are minor compared to operational dwelling, suggesting TEC mismatch is the dominant mechanism responsible for degradation during cycling.…”

Section: 37supporting

confidence: 65%

“…Recent developments in lab-based techniques have produced a host of X-ray CT instruments capable of imaging across multiple lengthscales without the destruction of the sample or the need to access synchrotron facilities. [14][15][16] SOFC anode performance is known to reduce through several degradation mechanisms during operational cycling as summarized z E-mail: p.shearing@ucl.ac.uk by Yokokawa et al 17 Recent studies by Song et al have suggested that the volume changes associated with anode oxidation cycling may result in the delamination and detachment of the metal from the ceramic.18 A similar mechanism is thought to occur during thermal cycling due to the TEC mismatch between the metal and ceramic, as investigated through complex 3D models by Clague et al 19 and Celik et al 20 Although the addition of YSZ to the anode is thought to reduce macroscopic expansion mismatch during thermal cycling, diffraction techniques have found expansion-induced stress to remain problematic, often producing complex, non-linear strain. 21,22 The addition of a YSZ skeleton to the anode is also thought to inhibit the sintering of the Ni metal, however, sintering remains a significant source of impedance during long-duration operation.…”

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confidence: 99%

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Thermally Driven SOFC Degradation in 4D: Part I. Microscale

Heenan¹,

Lu²,

Iacoviello³

et al. 2018

J. Electrochem. Soc.

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Solid oxide fuel cells (SOFCs) still suffer from many performance and lifetime issues due to complex degradation mechanisms such as sintering and delamination, particularly when exposed to high thermal ramp rates. This work presents the first of a twopart study investigating such degradation with a focus on the microscale. It is found that, compared to long-duration operation, nickel sintering during start-up and shut-down is minor even at low ramp-rates (3 • C·min −1 ). Moreover, thermal ramp-rates during heating have a negligible influence on the extent of particle-particle delamination during operational cycling; a similar magnitude of Ni-YSZ interfacial particle contact loss is observed after each thermal cycle for ramp rates from 3−30 • C·min −1 . Tortuosity-factor and percolation values remain consistent after the first thermal cycle, where Ni mobility may homogenize the structure during low ramp-rates. Both sintering and delamination are correlated to the triple-phase boundary (TPB) losses but for operational thermal cycling with minor dwell times, the particle-particle delamination is the prominent mechanism. This two-part study is the first report of an extended 4D analysis into the effects of thermal cycling on the anode structure with sub-micron resolution using only lab-based instruments. These findings will lead to improved cell designs, ultimately extending device lifetimes. SOFCs can provide energy for a large range of applications although cost and durability issues continue to obstruct entry to the mass-market. Moreover, in order to compete with existing technologies, many applications require rapid operational start-up and shutdown times which often necessitates high thermal ramp-rates, accelerating degradation. Therefore great effort has been applied in the pursuit of improved understanding of the processes responsible for losses in cell performance during operational cycling. High-temperature fuel cells such as the solid oxide fuel cell (SOFC) allow fast reaction kinetics, fuel versatility and high net efficiencies without the need for expensive catalysts.1 However, an inability to withstand thermal cycling due to the mismatch in the thermal expansion coefficients (TECs) of the constituent materials remains a prominent source of cell degradation. 2-4The reaction sites within the electrodes are named the triple-phase boundaries (TPBs), due to the three transport networks which are essential in the production of current from an SOFC: the transport of electrons through the metal, oxide ions (O 2− ) through the ceramic and gaseous reactants/products through the pores. The location where these three networks meet is where the TPB is located and is characterized by a one-dimensional reaction site length (L TPB ). In order to compare the population of TPBs between different electrodes the TPB density (ρ T P B ), the L TPB per unit volume, has become a common metric in the assessment of electrode performance. 5Recent advancements in characterization techniques have produced several methods for the qu...

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Section: 37supporting

confidence: 65%

mentioning

confidence: 99%

Thermally Driven SOFC Degradation in 4D: Part I. Microscale

Heenan¹,

Lu²,

Iacoviello³

et al. 2018

J. Electrochem. Soc.

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“…3D visualization techniques have been employed for both the anode and the cathode microstructures [10,11]. Clague et al [16] investigated the microstructure of the anode electrode with FIB-SEM microscope in order to obtain the representative volume element for the numerical analysis of the stresses at Ni and YSZ interfaces. Gunda et al [17] used 3D microstructural visualization technique for the LSM cathode again employing FIB-SEM and a digital filtering algorithm for better presentation of the microstructure.…”

Section: Introductionmentioning

confidence: 99%

Three dimensional stress analysis of solid oxide fuel cell anode micro structure

Çelik

İbrahimoğlu

Toros

et al. 2014

International Journal of Hydrogen Energy

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“…A variety of tomographic methods have been applied to battery electrodes to better understand these complex heterogeneous microstructures by facilitating evaluation of porosity, tortuosity, and surface area, and to inform more realistic models of electrode function and failure. X-ray tomography has been used to non-destructively reconstruct composite electrodes [39,40] [42,43]. Clague et al converted this 3-D structure into a mesh for finite element (FE) simulation of stresses developing within the material as temperature increased.…”

Section: Chemical Structural and Morphologicalmentioning

confidence: 99%

“…Clague et al concluded from a three-dimensional finite element model of a Ni-YSZ half cell constructed from FIB data that stresses arising at the Ni-YSZ interface due to thermal expansion were in excess of the yield stress of Ni, and that plastic deformation was a likely mechanism to relieve stresses during temperature change [43]. Atkinson and Ramos found that the stresses induced by chemical expansion across the membranes of fuel cells in planar or cylindrical geometries were very similar, but that ceria would likely not be mechanically stable above 750 • C, while perovskite-structured oxides would be stable up to higher temperatures [138].…”

Section: Chemical Expansion In Ionically Conductive Ceramicsmentioning

confidence: 99%

Chemomechanics of ionically conductive ceramics for electrical energy conversion and storage

et al. 2014

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Functional materials for energy conversion and storage exhibit strong coupling between electrochemistry and mechanics. For example, ceramics developed as electrodes for both solid oxide fuel cells and batteries exhibit cyclic volumetric expansion upon reversible ion transport. Such chemomechanical coupling is typically far from thermodynamic equilibrium, and thus is challenging to quantify experimentally and computationally. In situ measurements and atomistic simulations are under rapid development to explore how this coupling can be used to potentially improve both device performance and durability. Here, we review the commonalities of coupling between electrochemical and mechanical states in fuel cell and battery materials, illustrating with specific cases the progress in materials processing, in situ characterization, and computational modeling and simulation. We also highlight outstanding questions and opportunities in these applications -both to better understand the limiting mechanisms within the materials and to significantly advance the durability and predictability of device performance required for renewable energy conversion and storage.

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Stress analysis of solid oxide fuel cell anode microstructure reconstructed from focused ion beam tomography

Cited by 38 publications

References 16 publications

Thermally Driven SOFC Degradation in 4D: Part I. Microscale

Thermally Driven SOFC Degradation in 4D: Part I. Microscale

Three dimensional stress analysis of solid oxide fuel cell anode micro structure

Chemomechanics of ionically conductive ceramics for electrical energy conversion and storage

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