In situ transformation of amorphous gels into spherical aggregates of kaolinite: A HRTEM study (Articolo in rivista)

Type
Label
  • In situ transformation of amorphous gels into spherical aggregates of kaolinite: A HRTEM study (Articolo in rivista) (literal)
Anno
  • 2004-01-01T00:00:00+01:00 (literal)
Alternative label
  • Huertas FJ, Fiore S, Linares J (2004)
    In situ transformation of amorphous gels into spherical aggregates of kaolinite: A HRTEM study
    in Clay minerals (Print)
    (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori
  • Huertas FJ, Fiore S, Linares J (literal)
Pagina inizio
  • 423 (literal)
Pagina fine
  • 431 (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#numeroVolume
  • 39-4 (literal)
Rivista
Note
  • ISI Web of Science (WOS) (literal)
Titolo
  • In situ transformation of amorphous gels into spherical aggregates of kaolinite: A HRTEM study (literal)
Abstract
  • Initial stages of the gel-to-kaolinite transformation were Studied using HRTEM. Spherical aggregates of kaolinite crystals were produced during the synthesis of kaolinite by hydrothermal treatment of Si-Al amorphous gels. Prior to sphere formation, gels transform into pseudospherical domains that have a Si/Al ratio of one and display no SAED pattern. The spherical particles consist of radially arranged sectors of stacks of planar crystallites. Crystals display nonbasal spacings of 4.5, 4.2 and 3.8 Angstrom and a basal spacing of 7.1 Angstrom, the c* axis following the radius of the sphere. Interpretation of the 3D nanostructure of the spheres is difficult. The c* axis exhibits a radial disposition, but the relative orientation of the a* and b* axes in neighbouring crystallites may produce bent layers or incoherent contacts. In addition, curved layers with a d spacing of 7.4 Angstrom may be attributed to halloysite layers collapsed under microscopy conditions. The disappearance of the spheres during the hydrothermal treatment is probably due to preferential dissolution of either high-stress areas near bent layers or non-crystalline material filling crystal boundaries. Dissolution leads to sphere disaggregation and allows the component columnar crystals to continue to grow. Observations of the gel matrix suggest that under our experimental conditions kaolinite crystallizes via an in situ transformation of the gel. (literal)
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