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@PHDTHESIS{Ramasamy:827514,
      author       = {Ramasamy, Madhumidha},
      title        = {{D}ual {P}hase {O}xygen {T}ransport {M}embrane for
                      {E}fficient {O}xyfuel {C}ombustion},
      volume       = {351},
      school       = {Universität Bochum},
      type         = {Dr.},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2017-01634},
      isbn         = {978-3-95806-196-5},
      series       = {Schriften des Forschungszentrums Jülich Reihe Energie $\&$
                      Umwelt / Energy $\&$ Environment},
      pages        = {VIII, 136 S.},
      year         = {2016},
      note         = {Universität Bochum, Diss., 2016},
      abstract     = {Oxygen transport membranes (OTMs) are attracting great
                      interest for the separation of oxygenfrom air in an energy
                      efficient way. A variety of solid oxide ceramic materials
                      that possess mixed ionic and electronic conductivity (MIEC)
                      are being investigated for efficient oxygen separation (Betz
                      '10, Skinner '03). Unfortunately these materials do not
                      exhibit high degradation stability under harsh ambient
                      conditions such as flue gas containing C$_{2}$, SO$_{x}$,
                      H$_{2}$O and dust, pressure gradients and high temperatures
                      that are typical in fossil fuel power plants. For this
                      reason, dual phase composite membranes are developed to
                      combine the best characteristics of different compounds to
                      achieve high oxygen permeability and sufficient chemical and
                      mechanical stability at elevated temperatures. In this
                      thesis, the dual phase membrane
                      Ce$_{0.8}$Gd$_{0.2}$O$_{2-\delta}$ - FeCo$_{2}$O$_{4}$
                      (CGO-FCO) was developed after systematic investigation of
                      various combinations of ionic and electronic conductors. The
                      phase distribution of the composite was investigated in
                      detail using electron microscopes and this analysis revealed
                      the phase interaction leading to grain boundary rock salt
                      phase and formation of perovskite secondary phase. A
                      systematic study explored the onset of phase interactions to
                      form perovskite phase and the role of this unintended phase
                      as pure electronic conductor was identified. Additionally
                      optimization of conventional sintering process to eliminate
                      spinel phase decomposition into rock salt was identified. An
                      elaborate study on the absolute minimum electronic conductor
                      requirement for efficient percolation network was carried
                      out and its influence on oxygen flux value was measured.
                      Oxygen permeation measurements in the temperature range of
                      600 °C - 1000°C under partial pressure gradient provided
                      by air and argonas feed and sweep gases are used to identify
                      limiting transport processes. The dual phase membranes are
                      much more prone to surface exchange limitations because of
                      the limited length of the active triple phase boundaries. A
                      porous catalytic layer made of a single phase MIEC material,
                      i.e. LSCF, showed evidence of these limitations even when
                      using 1 mm thick samples. The dual phase composites were
                      also subjected to thermo-chemical stability in flue gas
                      conditions and mechanical stability under high pressure
                      applications. Microstructure variation based on different
                      powder synthesis routes of the composite impacting oxygen
                      permeation has been investigated. On the other hand,
                      microstructure variation via alternate densification/
                      sintering techniques such as hot pressing and SPS/FAST were
                      also explored. The finalized dual phase composition was
                      developed into thin film supported membrane layers. An
                      oxygen flux of 1.08 ml cm$^{-2}$ min$^{-1}$ was achieved on
                      an asymmetric membrane at 1015 °C successfully. However,
                      impregnation of catalysts into the porous support can
                      significantly improve the oxygen flux at lower temperatures,
                      overcoming the surface limitations at the interface between
                      the support and dense membrane.},
      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/827514},
}