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@PHDTHESIS{Schiek:809969,
      author       = {Schiek, Martin},
      title        = {{O}xidation {M}echanisms of {M}etallic {C}arrier
                      {M}aterials for {G}as {S}eparation {M}embranes},
      volume       = {316},
      school       = {Universität Bochum},
      type         = {Dr.},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2016-02859},
      isbn         = {978-3-95806-138-5},
      series       = {Schriften des Forschungszentrums Jülich Reihe Energie $\&$
                      Umwelt / Energy $\&$ Environment},
      pages        = {148 S.},
      year         = {2016},
      note         = {Universität Bochum, Diss., 2016},
      abstract     = {A major goal of research worldwide is the development of
                      new concepts for reducing CO$_{2}$ emissions in power plants
                      and other industry sectors. Very promising concepts are the
                      “carbon capture and storage” (CCS) technologies. These
                      contain gas separation units requiring the use of gas
                      separation membranes. The need to reduce membrane thickness
                      in combination with a high susceptibility for
                      mechanically-induced failure of the ceramic membrane
                      material makes the use of a metallic support structure for
                      the membranes necessary. The requirements for the supports
                      can be fulfilled by $\alpha$-Al$_{2}$O$_{3}$ forming
                      NiCrAl-base alloys. The membrane carriers have to withstand
                      different aggressive atmospheres at temperatures up to
                      1000°C. As the formation of a protective Al$_{2}$O$_{3}$
                      surface scale is crucial for the operation of the membrane
                      carrier, the present study deals with the influence of
                      temperature and gas atmosphere on the selective oxidation of
                      aluminum thereby using the commercially available alloys 602
                      CA and Haynes 214 with different aluminum contents of 2.4
                      wt.-\% and 4.5 wt.-\%, respectively. As these amounts are
                      far below the high aluminum contents of MCrAlY alloys (10
                      – 13 wt.-\% Al) considered as promising materials for the
                      useas support structure, the investigation of possible
                      effects of gas composition and/ortemperature on the
                      protective Al2O3 scale formation was possible in relatively
                      short-termexperiments (up to 1000 h). The studies were
                      focused on the temperature range 800 – 1100°C in
                      different atmospheres. During 800°C exposure Alloy 602 CA
                      formed a protective external Al$_{2}$O$_{3}$ scale
                      independent of the test gas used mainly due to the
                      beneficial effect of surface cold work while Haynes 214
                      showed initially Al$_{2}$O$_{3}$ formation but after 1000 h
                      exposure in Ar-20\%O$_{2}$ significant internal oxidation of
                      aluminum due to the formation of $\gamma$´-precipitates. It
                      was suggested that the aluminum concentration in γ is
                      crucial for the formation of an Al2O3 layer and not the bulk
                      alloy concentration. In addition, also the concentration of
                      other alloying elements affects the formation of an external
                      Al2O3 scale. In contrast to the behavior at 800°C, Alloy
                      602 CA exhibited at 900 – 1100°C internal Al2O3 nodules,
                      whose amount increased with increasing exposure temperature,
                      whereas Haynes 214 formed after initial internal oxidation
                      of aluminum a continuous Al2O3 layer in Ar-20\%O$_{2}$. A
                      mechanism describing the oxidation processes in Haynes 214
                      at 800 – 1100°C in Ar-20\%O$_{2}$ was proposed. Exposure
                      of Haynes 214 in different H$_{2}$O containing gases
                      revealed an increased tendency to internal oxidation of
                      aluminum in the absence of O$_{2}$ in the test gas possibly
                      due to hydrogen diffusion into the alloy. Furthermore, a
                      lower pO$_{2}$ was proposed to suppress or decrease the
                      growth rate of NiO to a larger extent than that of
                      Al$_{2}$O$_{3}$ and therefore promote the formation of an
                      external Al$_{2}$O$_{3}$ scale. Investigations on Haynes 224
                      showed that, despite its lower aluminum content compared to
                      Haynes 214 the material exhibited after 72 h oxidation at
                      800 – 1100°C always an external Al$_{2}$O$_{3}$ formation
                      with different amounts of Cr-rich transient oxide. It was
                      proposed that the addition of iron, results in a lower
                      amount of Al-rich $\gamma$´-precipitates in Haynes 224
                      compared to Haynes 214 thus increasing the tendency to
                      external Al$_{2}$O$_{3}$ formation.},
      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)11},
      url          = {https://juser.fz-juelich.de/record/809969},
}