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@PHDTHESIS{Sietmann:906137,
      author       = {Sietmann, Michael},
      title        = {{P}otentialfeldmessungen zur {Q}ualitätsbewertung von
                      {B}ipolarplatten},
      volume       = {564},
      school       = {RWTH Aachen},
      type         = {Dissertation},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2022-01250},
      isbn         = {978-3-95806-606-9},
      series       = {Schriften des Forschungszentrums Jülich. Reihe Energie
                      $\&$ Umwelt / Energy $\&$ Environment},
      pages        = {ix, 160 S.},
      year         = {2021},
      note         = {RWTH Aachen, Diss., 2021},
      abstract     = {To make fuel cells accessible to a broader application,
                      cost reduction is necessary. An important component of the
                      fuel cell with great cost reduction potential is the bipolar
                      plate. At the same time, the quality of the bipolar plate is
                      of decisive importance for the function of a fuel cell and
                      its longevity. New test methods are needed for the quality
                      assurance of the bipolar plate. In this work, a method and a
                      test setup based on the propagation of the electric
                      potential field is developed for the detection of defects in
                      graphite composite bipolar plates and bipolar plate
                      materials. A current is passed through the bipolar plate via
                      a point contact. With measuring points around the contacting
                      point, the potential field in the bipolar plate can be
                      recorded and analyzed for disturbances. Central elements of
                      the test setup are two probes with 25 spring-loaded
                      measuring tips, which are moved over the bipolar plate.
                      Depending on the programming, the measuring tips conduct a
                      current through the sample or measure the potential field
                      forming in the sample. X-ray tomography and electrical
                      potential simulations are used as a reference and to
                      evaluate the measurement results of the test setup. The
                      measurement method is tested and potential measurement
                      uncertainties are identified on material strips of blank
                      plates with through holes as defined artificial defects. A
                      complex electrical conductivity network is formed in the
                      graphite composite bipolar plates by the graphite particles.
                      The conductivity network becomes visible as measurement
                      noise in the results of the potential field measurements.
                      The application of the measurement method to bipolar plates
                      is demonstrated on monopolar plates withone-sided flow
                      field, in which artificial defects are imitated by plastic
                      accumulations, admixed wood and steel particles. The plastic
                      accumulations represent non-conductive regions in the
                      bipolar plate and the wood particles represent isolated
                      defects such as cracks, voids or non-conductive foreign
                      bodies. Massive defects such as plastic accumulations can be
                      identified with the test setup and their local
                      manifestations determined. Isolated defects, on the other
                      hand, are not detected with the test setup. Ohmic resistance
                      measurements on the monopolar plates and cutouts from the
                      monopolar plates prove that only large-scale defects have a
                      negative influence on the electrical conductivity of bipolar
                      plates. Fuel cell tests with the monopolar plates confirm
                      the results of the ohmic resistance measurements, according
                      to which isolated defects have no influence on ohmic
                      resistance and fuel cell performance. The developed test
                      set-up is suitable for random measurement of electrical
                      properties and detection of performance-impairing defects in
                      bipolar plates.},
      cin          = {IEK-14},
      cid          = {I:(DE-Juel1)IEK-14-20191129},
      pnm          = {1231 - Electrochemistry for Hydrogen (POF4-123)},
      pid          = {G:(DE-HGF)POF4-1231},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
      urn          = {urn:nbn:de:0001-2022040529},
      url          = {https://juser.fz-juelich.de/record/906137},
}