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@PHDTHESIS{Stournari:283575,
      author       = {Stournari, Vasiliki Kallirroi},
      title        = {{T}hermo-mechanical {P}roperties of {M}ixed
                      {I}onic-{E}lectronic {C}onducting {M}embranes for {G}as
                      {S}eparation},
      volume       = {304},
      school       = {RWTH Aachen},
      type         = {Dr.},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2016-01889},
      isbn         = {978-3-95806-117-0},
      series       = {Schriften des Forschungszentrums Jülich Reihe Energie $\&$
                      Umwelt / Energy $\&$ Environment},
      pages        = {167 S.},
      year         = {2016},
      note         = {RWTH Aachen, Diss., 2015},
      abstract     = {In this work membrane materials with mixed ionic /
                      electronic and protonic / electronic conductivity for oxygen
                      (Oxygen Transport Membranes - OTM) and hydrogen separation
                      (Hydrogen Transport Membranes - HTM) were investigated
                      regarding the thermo-mechanical properties. In case of OTM,
                      perovskite-type materials
                      Ba$_{0.5}$Sr$_{0.5}$(Co$_{0.8}$Fe$_{0.2}$)$_{1-x}$Zr$_{x}$O$_{3-\delta}$
                      (BSCF·Z100x), where x = 0.01, 0.03, 0.05 and 0.1, as well
                      as alternative SrTi$_{1-x}$Fe$_{x}$O$_{3-\delta}$
                      (ST·F100x) with x= 0.03, 0.05 and 0.07, while the fluorite
                      structured La$_{5.4}$WO$_{12-\delta}$ (LWO54) and
                      Nd$_{5.5}$WO$_{12-\delta}$ (NWO55) were investigated as HTM
                      membrane materials. Compressive creep tests were carried out
                      for all compounds in different temperature (900 – 1450
                      °C)and stress regimes (20 – 100 MPa) in air, vacuum and
                      Ar / 4 \% H$_{2}$ 2.5 \% H$_{2}$O-atmosphere. The observed
                      activation energies and stress exponents point to
                      diffusional creep as the predominant creep mechanism. In
                      case of BSCF-Z100·x ceramics, this was further supported by
                      the fact that the grain-size-normalized steady-state creep
                      ratevaries little for the different BSCF-Z100·x
                      compositions. It was confirmed that Zr substitution does not
                      significantly affect the thermal hysteresis of the creep
                      behavior as observed for pure BSCF. Regarding ST∙F100x and
                      LWO54 materials all materials maintained their main
                      structure after the tests. Coming to the HTM materials, the
                      creep mechanism for LWO54 was suggested to be cation aided
                      diffusion with a common migration of La$^{3+}$ / W$^{6+}$ as
                      rate controlling species along grain boundaries / through
                      lattice. ST∙F100x, LWO54 and NWO55 materials are promising
                      membrane materials regarding creep resistance. Elastic and
                      fracture properties were determined for dense and porous
                      tape casted LWO54. Young’s moduli via Vickers indentation,
                      ring-on-ring and impulse excitation technique at room and
                      elevated temperatures show a decrease by ~ 20 \% when the
                      material is heated up from room temperature to 1000 °C in
                      air and Ar / 4 \% H$_{2}$ atmosphere. Strength decreases by
                      ~30 \% when it is heated up to 1000 °C in air for dense
                      materials while at room temperature it can be increased by a
                      factor ~ 2 for homogeneous microstructure. Subsequent
                      fractographic analysis reveals agglomerates of large
                      irregular pores as fracture origins. For porous LWO54 the
                      strength is decreasing with porosity and the presence of the
                      secondary phase La$_{6}$W$_{2}$O$_{15}$. Micromechanical
                      properties at room temperature by Vickers indentation test
                      are also determined.},
      cin          = {IEK-2},
      cid          = {I:(DE-Juel1)IEK-2-20101013},
      pnm          = {899 - ohne Topic (POF3-899) / HITEC - Helmholtz
                      Interdisciplinary Doctoral Training in Energy and Climate
                      Research (HITEC) (HITEC-20170406)},
      pid          = {G:(DE-HGF)POF3-899 / G:(DE-Juel1)HITEC-20170406},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
      url          = {https://juser.fz-juelich.de/record/283575},
}