@article{ToetzkeGaiselmannOsenbergetal.2016,
  author    = {T{\"o}tzke, Christian and Gaiselmann, G. and Osenberg, M. and Arlt, T. and Mark{\"o}tter, H. and Hilger, A. and Kupsch, Andreas and M{\"u}ller, B. R. and Schmidt, V. and Lehnert, W. and Manke, Ingo},
  title     = {Influence of hydrophobic treatment on the structure of compressed gas diffusion layers},
  series = {Journal of power sources : the international journal on the science and technology of electrochemical energy systems},
  volume    = {324},
  journal   = {Journal of power sources : the international journal on the science and technology of electrochemical energy systems},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0378-7753},
  doi       = {10.1016/j.jpowsour.2016.05.118},
  pages     = {625 -- 636},
  year      = {2016},
  abstract  = {Carbon fiber based felt materials are widely used as gas diffusion layer (GDL) in fuel cells. Their transport properties can be adjusted by adding hydrophobic agents such as polytetrafluoroethylene (PTFE). We present a synchrotron X-ray tomographic study on the felt material Freudenberg H2315 with different PIPE finishing. In this study, we analyze changes in microstructure and shape of GDLs at increasing degree of compression which are related to their specific PTFE load. A dedicated compression device mimicking the channel-land pattern of the flowfield is used to reproduce the inhomogeneous compression found in a fuel cell. Transport relevant geometrical parameters such as porosity, pore size distribution and geometric tortuosity are calculated and consequences for media transport discussed. PTFE finishing results in a marked change of shape of compressed GDLs: surface is smoothed and the invasion of GDL fibers into the flow field channel strongly mitigated. Furthermore, the PTFE impacts the microstructure of the compressed GDL. The number of available wide transport paths is significantly increased as compared to the untreated material. These changes improve the transport capacity liquid water through the GDL and promote the discharge of liquid water droplets from the cell. (C) 2016 Elsevier B.V. All rights reserved.},
  language  = {en}
}
@article{ToetzkeMankeGaiselmannetal.2015,
  author    = {T{\"o}tzke, Christian and Manke, Ingo and Gaiselmann, Gerd and Bohner, John and M{\"u}ller, Bernd R. and Kupsch, Andreas and Hentschel, Manfred P. and Schmidt, Volker and Banhart, Jens and Lehnert, Werner},
  title     = {A dedicated compression device for high resolution X-ray tomography of compressed gas diffusion layers},
  series = {Review of scientific instruments : a monthly journal devoted to scientific instruments, apparatus, and techniques},
  volume    = {86},
  journal   = {Review of scientific instruments : a monthly journal devoted to scientific instruments, apparatus, and techniques},
  number    = {4},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {0034-6748},
  doi       = {10.1063/1.4918291},
  pages     = {6},
  year      = {2015},
  abstract  = {We present an experimental approach to study the three-dimensional microstructure of gas diffusion layer (GDL) materials under realistic compression conditions. A dedicated compression device was designed that allows for synchrotron-tomographic investigation of circular samples under well-defined compression conditions. The tomographic data provide the experimental basis for stochastic modeling of nonwoven GDL materials. A plain compression tool is used to study the fiber courses in the material at different compression stages. Transport relevant geometrical parameters, such as porosity, pore size, and tortuosity distributions, are exemplarily evaluated for a GDL sample in the uncompressed state and for a compression of 30 vol.\%. To mimic the geometry of the flow-field, we employed a compression punch with an integrated channel-rib-profile. It turned out that the GDL material is homogeneously compressed under the ribs, however, much less compressed underneath the channel. GDL fibers extend far into the channel volume where they might interfere with the convective gas transport and the removal of liquid water from the cell. (C) 2015 AIP Publishing LLC.},
  language  = {en}
}