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@ARTICLE{Krll:829608,
author = {Kröll, L. and de Haart, L.G.J. and Vinke, I. and Eichel,
Rüdiger-A.},
title = {{D}egradation {M}echanisms in {S}olid-{O}xide {F}uel and
{E}lectrolyzer {C}ells: {A}nalytical {D}escription of
{N}ickel {A}gglomeration in a {N}i / {Y} {S} {Z}
{E}lectrode},
journal = {Physical review applied},
volume = {7},
number = {4},
issn = {2331-7019},
address = {College Park, Md. [u.a.]},
publisher = {American Physical Society},
reportid = {FZJ-2017-03288},
pages = {044007},
year = {2017},
abstract = {The microstructural evolution of a porous electrode
consisting of a metal-ceramic matrix, consisting of nickel
and yttria-stabilized zirconia (YSZ), is one of the main
degradation mechanisms in a solid-oxide cell (SOC), in
either fuel cell or electrolyzer mode. In that respect, the
agglomeration of nickel particles in a SOC electrode leads
to a decrease in the electronic conductivity as well as in
the active catalytic area for the oxidation-reduction
reaction of the fuel-water steam. An analytical model of the
agglomeration behavior of a Ni/YSZ electrode is proposed
that allows for a quantitative description of the nickel
agglomeration. The accuracy of the model is validated in
terms of a comparison with experimental degradation
measurements. The model is based on contact probabilities of
nickel clusters in a porous network of nickel and YSZ,
derived from an algorithm of the agglomeration process. The
iterative algorithm is converted into an analytical
function, which involves structural parameters of the
electrode, such as the porosity and the nickel content.
Furthermore, to describe the agglomeration mechanism, the
influence of the steam content and the flux rate are taken
into account via reactions on the nickel surface. In the
next step, the developed agglomeration model is combined
with the mechanism of the Ostwald ripening. The calculated
grain-size growth is compared to measurements at different
temperatures and under low flux rates and low steam content,
as well as under high flux rates and high steam content. The
results confirm the necessity of connecting the two
mechanisms and clarify the circumstances in which the single
processes occur and how they contribute to the total
agglomeration of the particles in the electrode},
cin = {IEK-9},
ddc = {530},
cid = {I:(DE-Juel1)IEK-9-20110218},
pnm = {135 - Fuel Cells (POF3-135)},
pid = {G:(DE-HGF)POF3-135},
typ = {PUB:(DE-HGF)16},
UT = {WOS:000399821000001},
doi = {10.1103/PhysRevApplied.7.044007},
url = {https://juser.fz-juelich.de/record/829608},
}