2017-Sustainable Industrial Processing Summit
SIPS 2017 Volume 5. Marquis Intl. Symp. / New and Advanced Materials and Technologies
| Editors: | Kongoli F, Marquis F, Chikhradze N |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2017 |
| Pages: | 590 pages |
| ISBN: | 978-1-987820-69-0 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
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On the Mechanical Behavior of CGO-LSCF Coral Type Composite Coatings for Solid Oxide Fuel Cells
Amelia Almeida1; Jaroslaw Sar2; Elisabeth Djurado3; Rudy Ghisleny4;1INSTITUTO SUPERIOR TECNICO, Lisboa, Portugal; 2INSTITUTO SUPERIOR TECNICO (UNIVERSIDADE DE LISBOA) AND GRENOBLE INP (LEPMI), Lisboa, Portugal; 3GRENOBLE INP - LEPMI, St. Martin d'Heres, France; 4EMPA-SWISS FEDERAL LABORATORIES FOR MATERIALS TESTING AND RESEARCH, Thun, Switzerland (Confederation of Helvetia);
Type of Paper: Regular
Id Paper: 140
Topic: 43
Abstract:
The electrochemical performance of electrodes for solid oxide fuel cells (SOFC) requires porous structures with a large number of active triple phase boundaries. Further improvements require the development of new oxygen electrodes with highly porous structures able to enhance the adsorption process and provide high active zones for oxygen reduction. However, a high level of porosity leads to low mechanical properties that may compromise the electrodes integrity and cell performance that must be studied.
This work investigates the mechanical properties and behavior of CGO-LSCF composite coatings developed by electrostatic spray deposition as oxygen electrodes for intermediate temperature SOFC.
The coatings are characterized by a highly porous coral-like structure formed of aggregate nanoparticles that result in a very high surface area. Their mechanical behavior was studied by nanoscratch and nanoindentation tests and a model of material degradation under progressive compressive loading has been proposed. The coatings damage mechanism involves three regimes: at very low loads stresses are concentrated at the tips of individual corals that may fracture (regime I); as load increases, generalized fracture of the corals occurs and the material starts compacting into an increasingly dense layer (regime II); at the highest loads, the material behaves like an almost fully dense solid (regime III). As loading increases porosity decreases from 60 to about 5 vol% in the compacted material. The transitions between regimes are associated to increases in the contact stress and the same damage mechanisms are found during scratching and indentation. Hardness increases from about 2 to 100 MPa, while the Young's modulus varies in the range 1–18 GPa, as porosity decreases. Calculations of the real contact pressure allowed estimating a yield stress of 83 MPa that can be considered as a low limit for the materials fracture strength.