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@ARTICLE{Olguin:910145,
      author       = {Olguin, Gianni and Yacou, Christelle and Motuzas, J. and
                      Butterling, Maik and Meulenberg, Wilhelm A. and Smart, Simon
                      and Diniz da Costa, João C.},
      title        = {{S}urfactant functionalised cobalt silica membranes –
                      {G}as permeation and thin film positron annihilation
                      lifetime spectroscopy characterisation},
      journal      = {Journal of membrane science},
      volume       = {664},
      issn         = {0376-7388},
      address      = {New York, NY [u.a.]},
      publisher    = {Elsevier},
      reportid     = {FZJ-2022-03634},
      pages        = {121040 -},
      year         = {2022},
      abstract     = {This work investigates the use of positron annihilation
                      lifetime spectroscopy (PALS) for the in-situ structural
                      characterisation of silica derived thin film membranes. By
                      using a quantified maximum entropy method, PALS allowed for
                      the measurement of a pore size distribution depth profile.
                      PALS measurements were carried out on a series of silica
                      derived membranes where alumina supports were coated with
                      four layers of cationic HTBA surfactant cobalt silica sols
                      wherein the surfactant/cobalt molar ratio loading varied
                      from 0 to 3. PALS results showed that the coated layers
                      adjacent to the porous alumina substrate were characterised
                      by micropores and broad mesopores, a clear indication that
                      the porosity of the substrate affected the pore size at the
                      substrate and thin film interface. The last coated layer
                      resulted in a high concentration of ultra-micropores (dp < 6
                      Å). This was attributed to the surface smoothness conferred
                      by three previous coated layers. Higher surfactant loadings
                      resulted in an increase in gas permeation and reduction of
                      He/CO2 permselectivity from 91.5 to 3.8. A strong
                      correlation with R2 up to 0.999 was found between the
                      ultra-micropores in the top layer and gas permselectivity, a
                      clear indication that gas separation is controlled by small
                      pore sizes. In this work, PALS showed to be a powerful tool
                      for the characterisation of the structural features of thin
                      films.},
      cin          = {IEK-1},
      ddc          = {570},
      cid          = {I:(DE-Juel1)IEK-1-20101013},
      pnm          = {1232 - Power-based Fuels and Chemicals (POF4-123)},
      pid          = {G:(DE-HGF)POF4-1232},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000967940300007},
      doi          = {10.1016/j.memsci.2022.121040},
      url          = {https://juser.fz-juelich.de/record/910145},
}