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@INPROCEEDINGS{Weigelt:826651,
      author       = {Weigelt, Simone and Schlenz, Hartmut and König, Anna and
                      Heise, Henrike and Bosbach, Dirk},
      title        = {{S}tructural {C}haracterization of {G}eopolymers for the
                      {S}afe {D}isposal of the {F}ission {P}roducts 137{C}s and
                      90{S}r},
      reportid     = {FZJ-2017-00869},
      year         = {2016},
      abstract     = {Geopolymers are inorganic materials owning a high
                      variability in structure and composition. Their resistance
                      against heat and chemical attacks implies a high potential
                      regarding their use as nuclear waste forms. First
                      irradiation experiments by Lambertin et al. (J. Nuc. Mat.
                      2013, 443, 311-315) and Deng et al. (J. Nuc. Mat. 2015, 459,
                      270-275) confirmed a relatively high radiolysis
                      resistance.Metakaolin based geopolymers are aluminosilicates
                      with structural features of a three-dimensional network. The
                      negative charges arising from partial substitution of
                      tetravalent Si by trivalent Al are preferably balanced by
                      alkaline and alkaline earth cations. Therefore a durable
                      encapsulation and immobilization of the extremely mobile
                      radionuclides 137Cs and 90Sr is anticipated.For structural
                      characterization we synthesized geopolymers with varying
                      chemical composition by mixing different metakaolin and
                      kaolin powders with amorphous silica and alkaline solutions
                      containing Na, K, Rb and Cs, or Ca and Sr, in different
                      ratios, respectively. Additionally the water amount used for
                      the syntheses was varied, as well as temperature and
                      duration of thermal treatment during sample setting. Samples
                      were characterized by XRD, Raman, IR and MAS-NMR
                      spectroscopy, as well as SEM (EDX) and TG-DSC. MAS-NMR data
                      show an evolution of the geopolymers’ structure that
                      depends strongly on synthesis parameters and composition.
                      Inversion recovery studies reveal two different Cs species
                      with very similar signal positions, but different
                      longitudinal relaxation times and therefore different
                      magnetic vicinities. This might suggest mobile as well as
                      immobile cation species.},
      month         = {Jun},
      date          = {2016-06-05},
      organization  = {5th International ATALANTE Conference
                       on Nuclear Chemistry for Sustainable
                       Fuel Cycles, Montpellier (France), 5
                       Jun 2016 - 10 Jun 2016},
      subtyp        = {Other},
      cin          = {IEK-6 / ICS-6},
      cid          = {I:(DE-Juel1)IEK-6-20101013 / I:(DE-Juel1)ICS-6-20110106},
      pnm          = {161 - Nuclear Waste Management (POF3-161) / HITEC -
                      Helmholtz Interdisciplinary Doctoral Training in Energy and
                      Climate Research (HITEC) (HITEC-20170406)},
      pid          = {G:(DE-HGF)POF3-161 / G:(DE-Juel1)HITEC-20170406},
      typ          = {PUB:(DE-HGF)6},
      url          = {https://juser.fz-juelich.de/record/826651},
}