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@PHDTHESIS{Barrier:50675,
      author       = {Barrier, Diane Catherine},
      title        = {{C}haracterisation and fabrication of zirconia and thoria
                      based ceramics for nuclear applications},
      volume       = {4188},
      issn         = {0944-2952},
      school       = {Techn. Hochsch. Aachen},
      type         = {Dr. (FH)},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {PreJuSER-50675, Juel-4188},
      series       = {Berichte des Forschungszentrums Jülich},
      pages        = {165 p.},
      year         = {2005},
      note         = {Record converted from VDB: 12.11.2012; Aachen, Techn.
                      Hochsch., Diss., 2005},
      abstract     = {The reduction of the long term radiotoxicity of nuclear
                      waste during disposal is the aim of the research called
                      “Partitioning $\&$ Transmutation of minor actinides
                      (MAs)”, which also requires the development of inert
                      ceramic support materials. Moreover, after separation, if
                      the transmutation is not available, the actinides can be
                      conditioned into stable dedicated solid matrices
                      (Partitioning $\&$ Conditioning strategy).
                      Yttrium-stabilized zirconia and thoria are discussed in the
                      international nuclear community as candidates for the
                      fixation of long-lived actinides as target material for
                      transmutation and as stable materials for long-term final
                      disposal. The aims of the following work are twofold:
                      determine the impact of the addition of actinides, simulated
                      by cerium on the properties of the matrices and study the
                      possibility of synthesising homogeneous ceramics using
                      simple fabrication routes. Within this framework,
                      (Zr,Y)O$_{2-x}$ - CeO$_{2}$ and ThO$_{2}$ - CeO$_{2}$
                      powders with variable ceria contents (from 0 to 100 \%) were
                      synthesised by a co-precipitation method of nitrate
                      solution. The influence of ceria concentration on the
                      powder' properties, such as thermal behaviour and the
                      evolution of material crystallisation during annealing, was
                      investigated in detail by thermogravimetry (TG) coupled with
                      differential scanning calorimetry (DSC) and X-ray
                      diffraction (XRD). Both systems crystallise at high
                      temperature in a stable solid solution, fcc, fluorite type
                      structure and follow the Vegard’s law for the complete
                      range of ceria. For both systems a critical concentration of
                      20 mol \% has been established. For ceria concentrations
                      lower than 20 \%, the properties of the system are mainly
                      controlled by the matrix. Pellets with different ceria
                      concentrations were compacted from these powders by using
                      different technological cycles. In order to obtain materials
                      with reliable properties, the technological parameters of
                      each chosen fabrication route, have been optimised. By
                      employing mild wet methods (calcination at 600°C,
                      wet-grinding in acetone and fractionation in acetone),
                      (Zr,Y,Ce)O$_{2-x}$ pellets with densities of up to 0.97 TD
                      can be obtained. In the case of the (Th,Ce)O$_{2}$ system,
                      pressing by repressing from non-milled powder was selected
                      as the fabrication route, allowing the fabrication of
                      pellets with densities of up to 0.98 TD. In both cases,
                      materials with homogeneous repartition of pores, well formed
                      grains and boundaries and good mechanical properties were
                      obtained.},
      cin          = {ISR},
      cid          = {I:(DE-Juel1)VDB182},
      pnm          = {Nukleare Sicherheitsforschung},
      pid          = {G:(DE-Juel1)FUEK249},
      typ          = {PUB:(DE-HGF)11 / PUB:(DE-HGF)3},
      url          = {https://juser.fz-juelich.de/record/50675},
}