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Microscopic Analysis of Current and Mechanical Properties of Nafion® Studied by Atomic Force Microscopy
University of Applied Sciences Esslingen, Kanalstrasse 33, Esslingen 73728, Germany
German Aerospace Center, Institute of Technical Thermodynamics, Pfaffenwaldring 38-40, Stuttgart 70569, Germany
Institute for Thermodynamics and Thermal Engineering, University of Stuttgart, Stuttgart 70550, Germany
* Author to whom correspondence should be addressed.
Received: 9 July 2012; in revised form: 3 October 2012 / Accepted: 31 October 2012 / Published: 16 November 2012
Abstract: The conductivity of fuel cell membranes as well as their mechanical properties at the nanometer scale were characterized using advanced tapping mode atomic force microscopy (AFM) techniques. AFM produces high-resolution images under continuous current flow of the conductive structure at the membrane surface and provides some insight into the bulk conducting network in Nafion membranes. The correlation of conductivity with other mechanical properties, such as adhesion force, deformation and stiffness, were simultaneously measured with the current and provided an indication of subsurface phase separations and phase distribution at the surface of the membrane. The distribution of conductive pores at the surface was identified by the formation of water droplets. A comparison of nanostructure models with high-resolution current images is discussed in detail.
Keywords: Nafion; AFM; current; adhesion; stiffness; nanostructure; model
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Hiesgen, R.; Helmly, S.; Galm, I.; Morawietz, T.; Handl, M.; Friedrich, K.A. Microscopic Analysis of Current and Mechanical Properties of Nafion® Studied by Atomic Force Microscopy. Membranes 2012, 2, 783-803.
Hiesgen R, Helmly S, Galm I, Morawietz T, Handl M, Friedrich KA. Microscopic Analysis of Current and Mechanical Properties of Nafion® Studied by Atomic Force Microscopy. Membranes. 2012; 2(4):783-803.
Hiesgen, Renate; Helmly, Stefan; Galm, Ines; Morawietz, Tobias; Handl, Michael; Friedrich, K. A. 2012. "Microscopic Analysis of Current and Mechanical Properties of Nafion® Studied by Atomic Force Microscopy." Membranes 2, no. 4: 783-803.