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Coatings 2018, 8(12), 450; https://doi.org/10.3390/coatings8120450 (registering DOI)

Layer Formation from Polymer Carbon-Black Dispersions

1
Forschungszentrum Jülich Gmbh Institute of Energy and Climate Research, Electrochemical Process Engineering (IEK-3), 52425 Jülich, Germany
2
Faculty of Mechanical Engineering, RWTH Aachen, 52062 Aachen, Germany
3
Chair for Fuel Cells, RWTH Aachen, 52062 Aachen, Germany
*
Author to whom correspondence should be addressed.
Received: 19 October 2018 / Revised: 29 November 2018 / Accepted: 6 December 2018 / Published: 7 December 2018
PDF [904 KB, uploaded 7 December 2018]

Abstract

It has been well-established that effects such as cracking are observable when wet layers are dried. In particular, the layer thickness, as well as the surface tension of the liquid, is responsible for this behavior. The layer formation of polymer electrolyte fuel cells and electrolyzer electrodes, however, has not yet been analyzed in relation to these issues, even though the effect of cracks on cell performance and durability has been frequently discussed. In this paper, water propanol polymer-containing carbon-black dispersions are analyzed in situ with regard to their composition during drying. We demonstrate that crack behavior can be steered by slight variations in the initial dispersion when the solvent mixture is near the dynamic azeotropic point. This minor adjustment may strongly affect the drying behavior, leading to either propanol or water-enriched liquid phases at the end of the drying process. If the evaporation of the solvent results in propanol enrichment, the critical layer thickness at which cracks occur will be increased by about 30% due to a decrease in the capillary pressure. Microscopic images indicate that the crack area ratio and width depend on the wet layer thickness and initial liquid phase composition. These results are of much value for future electrode fabrication, as cracks affect electrode properties.
Keywords: PEM fuel cell; PEM electrolysis; layer drying; layer cracking; crack analysis; slot die coating PEM fuel cell; PEM electrolysis; layer drying; layer cracking; crack analysis; slot die coating
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Scheepers, F.; Stähler, A.; Stähler, M.; Carmo, M.; Lehnert, W.; Stolten, D. Layer Formation from Polymer Carbon-Black Dispersions. Coatings 2018, 8, 450.

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