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@PHDTHESIS{Niehoff:200847,
      author       = {Niehoff, Patrick},
      title        = {{E}ntwicklung planarer
                      {B}a$_{0,5}${S}r$_{0,5}${C}o$_{0,8}${F}e$_{0,2}${O}$_{3-δ}$
                      - {M}embranmodule zur {S}auerstoffabtrennung und {A}nalyse
                      ihres {T}ransportverhaltens},
      volume       = {256},
      school       = {Ruhr-Universität Bochum},
      type         = {Dissertation},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2015-03226},
      isbn         = {978-3-95806-044-9},
      series       = {Schriften des Forschungszentrums Jülich Reihe Energie $\&$
                      Umwelt / Energy $\&$ Environment},
      pages        = {VIII, 134 S.},
      year         = {2015},
      note         = {Dissertation, Ruhr-Universität Bochum, 2015},
      abstract     = {Oxygen transport membranes (OTMs) represent a promising
                      alternative for the extraction of oxygen compared to energy
                      intensive processes such as the cryogenic air separation.
                      Especially ceramic, mixed ionic-electronic conducting
                      membranes (MIECs) are of current interest. Due to their
                      ability to transport oxygen via vacancies in the crystal
                      lattice in case of sufficient high temperature and partial
                      pressure gradients, such membranes can theoretically achieve
                      a selectivity of $100\%$ assuming the absence of any
                      leakages. With respect to membrane material, mostly
                      perovskites are used, showing high ionic and electronic
                      conductance. In this context, the perovskite with the
                      highest oxygen permeability is
                      Ba$_{0,5}$Sr$_{0,5}$Co$_{0,8}$Fe$_{0,2}$O$_{3-\delta}$
                      (BSCF), which is also used in this work. Regarding the
                      technical implementation, different design and operational
                      concepts exist, whereas the respective oxygen transport is
                      governed by a complex set of different mechanisms depending
                      on each individual membrane system’s architecture. One
                      part of this work addresses the modeling of the oxygen
                      transport through a supported membrane. For this purpose,
                      different approaches for individual transport mechanisms
                      such as solid state diffusion, surface exchange, and
                      transport in the support and gas phase are combined to one
                      comprehensive model. With regard to the surface exchange, a
                      correction factor is introduced, which takes into account
                      the realistic topography of the membrane surfaces. This
                      approach was verified by permeation measurements of
                      supported samples with varying membrane layer thicknesses (8
                      - 400 $\mu$m), showing a good agreement between model and
                      experiment. Characteristic values (porosity, tortuosity,
                      spec. surface area) necessary for the modeling were
                      determined using x-ray computed tomography. Overall the
                      complete model allows the description of experimental data
                      with a deviation of only 7\%. Another focal point of this
                      work is the development and testing of a complete ceramic
                      membrane module. The manufacturing of planar compounds (20
                      mm diameter) consisting of membrane- (thickness 25 $\mu$m)
                      and support-layers (thickness 1.4 mm) was done by sequential
                      tape casting and lamination. Also, the adaption of the
                      sintering program allows the fabrication of samples with a
                      surface area of 110 x 110 cm$^{2}$, thus confirming the
                      scalability of this manufacturing process. The compound’s
                      outer surface is sealed by applying a ceramic layer. For
                      this purpose, a BSCF-paste was developed and optimized with
                      regard to a maximum green density, resulting in a gastight,
                      crack-free layer with low porosity (ca. 5\%). A gastight
                      connection between BSCF-tube and compound was successfully
                      achieved by garnishing and subsequent sintering under load.
                      A tape-cast BSCF-foil (green thickness ca. 60 $\mu$m) is
                      used as joining material, yielding a high mechanical
                      stability and gas-tightness of the established connection.
                      The membrane-module’s oxygen permeation was measured in
                      3-end mode undervarying conditions and is compared to
                      reference samples. In this context, the results of the
                      module, the reference samples and the developed transport
                      model are consistent to each other. The viscous gas
                      transport within the support layer was identified as the
                      limiting factor. Thus future research and development needs
                      to focus on the optimization of the support’s
                      microstructure.},
      keywords     = {Dissertation (GND)},
      cin          = {IEK-1},
      cid          = {I:(DE-Juel1)IEK-1-20101013},
      pnm          = {113 - Methods and Concepts for Material Development
                      (POF3-113) / HITEC - Helmholtz Interdisciplinary Doctoral
                      Training in Energy and Climate Research (HITEC)
                      (HITEC-20170406)},
      pid          = {G:(DE-HGF)POF3-113 / G:(DE-Juel1)HITEC-20170406},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
      url          = {https://juser.fz-juelich.de/record/200847},
}