Characterization of warpage behaviour of Gd-doped ceria/NiO–yttria stabilized zirconia bi-layer samples for solid oxide fuel cell application

The need for understanding the mechanisms and optimization of shape distortions during sintering of bilayers is necessary while producing structures with functionally graded architectures. A finite element model based on the continuum theory of sintering was developed to understand the camber developments during sintering of bilayers composed of La0.85Sr0.15MnO3 and Ce0.9Gd0.1O1.95 tapes. Free shrinkage kinetics of both tapes were used to estimate the parameters necessary for the finite element models. Systematic investigations of the factors affecting the kinetics of distortions such as gravity and friction as well as the initial geometric parameters of the bilayers were made using optical dilatometry experiments and the model. The developed models were able to capture the observed behaviors of the bilayers’ distortions during sintering. Finally, we present the importance of understanding and hence making use of the effect of gravity and friction to minimize the shape distortions during sintering of bilayers.

Section: Introductionmentioning

confidence: 99%

Finite Element Modeling of Camber Evolution During Sintering of Bilayer Structures

Molla

Bulatova

et al. 2014

“…In today's energy efficient technologies, such as membrane and solid oxide fuel cell technologies, it is desirable to reduce the thickness of the individual layers to minimize diffusion resistance and increase the surface areas for better system performance. Sintering samples with such geometries is challenging, as shape instabilities often occur during sintering . Thus, an increased interest in simulating mechanical distortions during co‐sintering of multiple layer systems has arisen.…”

Section: Introductionmentioning

confidence: 99%

“…Sintering samples with such geometries is challenging, as shape instabilities often occur during sintering. [1][2][3][4] Thus, an increased interest in simulating mechanical distortions during co-sintering of multiple layer systems has arisen.…”

Section: Introductionmentioning

confidence: 99%

Modeling Sintering of Multilayers Under Influence of Gravity

Frandsen

Olevsky²,

Molla

et al. 2012

There is a tendency for multiple functional ceramic layers used in various applications to have increasing surface areas and decreasing thicknesses. Sintering samples with such geometry is challenging, as differential shrinkage of the layers causes undesired distortions. In this work, a model, which describes the combined effect of sintering and gravity of thin multilayers, is derived and later compared with experimental results. It allows for consideration of both uniaxial and biaxial stress states. The model is based on the Skorohod‐Olevsky viscous sintering framework, the classical laminate theory and the elastic‐viscoelastic correspondence principle. The modeling approach is then applied to illustrate the effect of gravity during sintering of thin layers of cerium gadolinium oxide (CGO), and it is found to be significant.

“…Various experimental methods based on contact and noncontact dilatometry have been developed to determine the necessary viscosity parameters. One of the earliest techniques used was sinter forging in which a compressive uniaxial constant load was applied on the compact and strains were measured continuously with time . The main challenge in this kind of characterization technique is to obtain reliable viscosity data while minimizing the influence of microstructure.…”

Section: Introductionmentioning

confidence: 99%

“…One of the earliest techniques used was sinter forging in which a compressive uniaxial constant load was applied on the compact and strains were measured continuously with time. 13,14 The main challenge in this kind of characterization technique is to obtain reliable viscosity data while minimizing the influence of microstructure. This can be done by applying a uniaxial load over a long time to obtain an estimable deformation which is above the background noise while still ensuring limited amount of time to avoid undesired anisotropy in the microstructure.…”

Section: Introductionmentioning

confidence: 99%

Camber Evolution and Stress Development of Porous Ceramic Bilayers During Co‐Firing

Esposito

Schmidt

et al. 2012

Camber evolution and stress development during co‐firing of asymmetric bilayer laminates, consisting of porous Ce0.9Gd0.1O1.95 gadolinium‐doped cerium oxide (CGO) and La0.85Sr0.15MnO3 lanthanum strontium manganate (LSM)‐CGO were investigated. Individual layer shrinkage was measured by optical dilatometer, and the uniaxial viscosities were determined as a function of layer density using a vertical sintering approach. The camber evolution in the bilayer laminates was recorded in situ during co‐firing and it was found to correspond well with the one predicted by the theoretical model. The estimated sintering mismatch stress in co‐fired CGO‐LSM/CGO bilayer laminates was significantly lower than general sintering stresses expected for free sintering conditions. As a result, no co‐firing defects were observed in the bilayer laminates, illustrating an acceptable sintering compatibility of the ceramic layers.