Strength and Toughness of Tape‐Cast Yttria‐Stabilized Zirconia

Selçuk, Ahmet; Atkinson, A.

doi:10.1111/j.1151-2916.2000.tb01507.x

Cited by 117 publications

(69 citation statements)

References 22 publications

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“…Data on the fracture toughness of the bulk or interfaces between the different SOFC materials is available. The former usually consists in measurements in mode I (opening) [32][33][34], while 4-point bending measurements of interfaces are characterised by mode mixity [35]. A consistent handling of delaminations [36] in SOFCs is beyond the scope of the present work, as it requires a precise knowledge of the stress field around the…”

Section: Assessment Of Mechanical Failuresmentioning

confidence: 99%

Sensitivity of Stresses and Failure Mechanisms in SOFCs to the Mechanical Properties and Geometry of the Constitutive Layers

2011

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A model based on the Euler–Bernoulli theory is used to assess the sensitivity of residual stresses in solid oxide fuel cells to the mechanical properties and geometry of the constituents. It considers different cell configurations, characterised by the presence or not of a compensating layer, and a cathode based on either lanthanum strontium manganite (LSM) or lanthanum strontium cobaltite ferrite (LSCF). The implementation of creep in the model provides insights into the parameters that affect the zero‐stress temperature and behaviour during ageing. The amount of irreversible deformation generated in the cell layers after the sintering step depends on the mechanical properties of the layers, type of cell and to some extent, cooling rate. X‐ray diffraction measurements from literature are used to verify the prediction. Depending on the mechanical properties, the stress state in the LSM cathode changes from tensile to compressive with respect to temperature. During combined ageing and thermal cycling, tensile stress might arise in the compatibility layer of LSCF‐based cells, due to the relief of the initial compressive stress at operating temperature. The Weibull analysis provides the assessment of mechanical failure. A simplified approach is used for buckling‐driven delamination, but the propagation of cracks is predicted for unlikely large pre‐existing defects.

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Section: Assessment Of Mechanical Failuresmentioning

confidence: 99%

Sensitivity of Stresses and Failure Mechanisms in SOFCs to the Mechanical Properties and Geometry of the Constitutive Layers

2011

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“…Substituting some typical values for the mechanical properties from Table 5 [43][44][45][46][47], an oxidation strain of 1% gives an extremely high electrolyte tensile stress of 2.2 GPa and a correspondingly small critical electrolyte thickness of only 0.074 lm. Therefore, this problem cannot be solved by reducing the electrolyte thickness, because such a thin, and at the same time dense, electrolyte is not technically feasible.…”

Section: Anode-supported Configurationmentioning

confidence: 99%

Redox Cycling of Ni‐Based Solid Oxide Fuel Cell Anodes: A Review

2007

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The published literature relating to damage to SOFCs caused by redox cycling of Ni‐based anodes is reviewed. The review covers the kinetics of Ni oxidation and NiO reduction (as single phases and as constituents of composites with yttria‐stabilised zirconia, YSZ), the dimensional changes associated with redox cycling and the effect of this on the mechanical integrity and electrical performance of cells and stacks. A critical parameter is the expansion strain that is caused by oxidation. Several studies report that the first complete oxidation of a Ni/YSZ composite causes a linear expansion of the order of 1%, but the actual values vary substantially between different investigations. The oxidation strain is the result of microstructural irreversibility during the redox process and leads to strain accumulation over several redox cycles. This can cause mechanical disruption to an anode, anode support or other cell components attached to the anode.A simplified mechanical model of the stress and damage that are likely to be caused by anode expansion is proposed and applied to anode‐supported, electrolyte‐supported and inert substrate‐supported cell configurations. This allows the maximum oxidation strain to avoid damage in each configuration to be estimated.

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“…The compressive stress due to electrolyte layer deposition of about 1 GPa [14] probably largely diminishes at operation temperatures [26]. The critical strain for electrolyte fracture at elevated temperature is around 0.17% [27], hence electrolyte cracking due to the oxidation induced strain could be expected, which was also observed (see below).…”

Section: Resultsmentioning

confidence: 84%