Advanced Diagnostics Tools and Analysis Methodologies in Solid Oxide - - PowerPoint PPT Presentation

Advanced Diagnostics Tools and Analysis Methodologies in Solid Oxide Fuel Cells

Mitglied der Helmholtz-Gemeinschaft

• 24. June 2009
• J. Malzbender, P. Batfalsky, L. Blum, S. M. Groß, V.A.C. Haanappel,
• N. H. Menzler, A. Neumann, V. Shemet, R.W. Steinbrech, I.C. Vinke

International Symposium on Diagnostics Tools for Fuel Cell Technologies, Trondheim 2009

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Role of “Advanced Diagnostics Tools and Methodologies” Post operation methodology Post operational analysis methods Post operation analysis procedure Example G-Design stack Improved design

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Role of “Advanced Diagnostics Tools and Methodologies”

Fabrication Design Post Operation Analyses Operation Light weight stack (APU application) Short stack for SOFC development

F-design CS-design

Diagnostics Tools / Methodologies

Advanced characterization methods are an essential element to understand the stack performance within the frame- work of a systematic testing

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Disassembling with selected experts depending on expected degradation

• mechanism. Experience in synthesis, production, interaction, thermo-

mechanics, corrosion, thermo-chemistry, sealants, stack / system

• peration, single cell testing, microscopy, SEM

108 dissections from 8.2002 to 9.2008. Electro-chemical results and irregular events are considered. A digital photographic image is taken of every stack plane. Unusual observations are investigated microscopically during disassembling. After dismantling more detailed SEM (TEM) investigation are carried out. Every stack opening is discussed in a subsequent meeting, suggesting further detailed follow up work. Reports are passed on to selected members of the SOFC development team. Selected results are presented to the entire SOFC team in semi-annual meetings.

Post Operation Methodologie

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Materialography & Image analysis Macroscopic changes, color SEM and EDX Microscopic / structural changes, qualitative chemical analysis, Wet chemical analysis quantitative, coarse localized SIMS quantitative, localized Thermography, computer tomography short circuit localization, porosity XRD structural changes TEM local changes, interfaces, reactions Leakage, liquid dye inspection localization of leakages

Post Operational Analysis Methods

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Post operation analysis procedure Example G-Design stack (G1002-04)

Investigation of degradation and failure by comparison of electrochemical results with stack dismantling results low power output G-Design problems : high degradation rate

200 400 600 800 1000 1200 1400 0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 1,1 1,2 0,0 0,2 0,4 0,6 0,8 1,0 1,2

Alterung 23.0 ± 0.1% in 1000 Stunden über 314 Stunden Alterung 35.3 ± 0.1% in 1000 Stunden über 644 Stunden Alterung 37.0 ± 0.3% in 1000 Stunden über 299 Stunden Alterung 10.4 ± 0.1% in 1000 Stunden über 803 Stunden Leck in der Dampfringleitung

Spannung / V Zeit / h Stromdichte / A/cm

2

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Before further dismantling took place the origin of the short circuiting was investigated using infrared camera imaging (thermography). Ceramic glue shows partly red coloring and bubbles. In addition a short circuiting to the next cassette was detected. Sealing of cell: ceramic glue Sealing to next layer: glass- ceramic

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D5 Origin of the short circuiting was a deformation

• f the manifold.

Mechanically damaged contact layer

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Cathode side ~ 3,5 - 4 mm ~ 0,2 – 0,3 mm Small contact width compared to standard design Stack G1002-3 Standard F2060-1 Air channel Air channel Contact Contact Air channel Trace of the contact width Origin of low power output

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Edge of the cell near the sealant

60 31.6 O Cr2O3 100 40 68.4 Cr K Form Comp. % Atom % Mass % Element

Formation of Cr2O3 on the electrolyte High degradation rate

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55.6 21.2 O La2O3 41.3 10.7 35.2 La L CuO 3.5 1.8 2.8 Cu K CoO 1.2 0.69 0.97 Co K MnO 32.8 19.5 25.4 Mn K Cr2O3 21.3 11.8 14.5 Cr K Form Comp. % Atom % Mass % Element

Modified contact layer

Einbettmasse Einbett masse

LCC10 New phases MnOx Crofer22 APU first

High degradation rate

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61.3 23.0 O La2O3 23.7 6.2 20.2 La L ZrO2 50.9 17.6 37.7 Zr L MnO 18.9 11.3 14.6 Mn K Cr2O3 6.5 3.7 4.5 Cr K Form Comp. % Atom % Mass % Element

Chromia composites near the three phase boundary High degradation rate

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Problem:

Short circuit due to local upwards bending

• f the manifold (creep effect)

Cr2O3 reaction products (from gas phase) were detected on the surface of the electrolyte New reaction products were detected in the contact layer (influence of the ceramic glue) Chromia composites were found near the three-phase boundary which might be associated with the high degradation

Solution:

Application glass-ceramic support point Substitution of ceramic glue by glass – ceramic sealant Components of the ceramic glue could be confirmed, a follow up stack in the same design with glass – ceramic sealant had a degradation of (2,6-2,8)% / 1000h compared to (23-35%).

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Cracks in cell, green color suggests re-oxidation Application point of glass-ceramic support point Manifold bend towards anode side Manifold bend towards anode side Application point of glass- ceramic support point

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Cut Air inlet Air outlet

Large manifold made from thin metal sheets is not geometrically stable at high temperatures Results are short circuit or cell fracture

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Improved Design

Using a combination of metallic and glass-ceramic sealants. Significantly reduced size of unsupported manifold. In addition asymmetric cell to permit smaller in-plane gradient on thermal cycling.

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Stack-Dismantling

Jürgen Malzbender Vincent Haanappel Norbert Menzler Peter Batfalsky Rolf Steinbrech Ico Vinke

Thank you for your attention