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Clays and Clay Minerals

, Volume 37, Issue 5, pp 396–402 | Cite as

Preparation and Characterization of Al-Rich Zn-Al Hydrotalcite-Like Compounds

  • F. Thevenot
  • R. Szymanski
  • P. Chaumette
Article

Abstract

Hydrotalcite-like compounds, described by the formula [Zn1-xAlx(OH)2][(CO3)x/2 · nH2O], were prepared by coprecipitation methods at 80°C and characterized by bulk chemical analysis, X-ray powder diffraction (XRD), nuclear magnetic resonance (NMR), and scanning-transmission electron microscopy (STEM). An x value of 0.33 was previously assumed to be an upper limit, but recently, Al-rich hydrotalcite-like compounds have been prepared with x as large as 0.44 by hydrothermal synthesis. In the Zn-Al system, Al-rich hydrotalcite was synthesized at normal pressure by coprecipitation. Zn-Al hydrotalcite-like compounds were obtained in the range of x = 0.3 to 0.4. An Al-rich hydrotalcite-like compound with x = 0.44 was formed in mixtures containing large amounts of a poorly crystalline Zn-Al phase. A continuous contraction of the hydrotalcite-like structure occurred as x increased, both the a and c lattice parameters decreasing for x values as large as 0.44. This study illustrates the advantages of using quantitative analytical electron microscopy with high spatial resolution to complement conventional (and bulk) characterization techniques for correlating structural and compositional characteristics of finely divided materials.

Key Words

Hydrotalcite Nuclear magnetic resonance Scanning-transmission electron microscopy Synthesis X-ray powder diffraction Zinc 

Résumé

Des composés de type hydrotalcite, de formule générale [Zn1-xAlx(OH)2][(CO3)x/2 · nH2O], ont été préparés par coprécipitation, à 80üC, et caractérisés par différentes techniques telles que: analyse chimique globale, diffraction des rayons-X (DRX), résonance magnétique nucléaire (RMN), et microscopie électronique à transmission (STEM). Jusqu’à présent, la valeur de 0.33 était la limite supérieure admise pour x, mais récemment des phases de type hydrotalcite riches en Al ont été préparées, pour x = 0.44, par synthèse hydrothermale. Pour le système Zn-Al, nos résultats montrent que des composés de type hydrotalcite riches en Al peuvent être synthéitsés à pression normale par coprécipitation. Des phases de type hydrotalcite à base de Zn et Al, ont été obtenues pour des valeurs de x comprises entre 0.3 et 0.4. Une phase hydrotalcite riche en Al avec x = 0.44 a été observée en mélange avec une grande quantité d’une phase à base de Zn et Al très mal cristallisée. Une contraction continue de la structure hydrotalcite est observée lorsque x augmente, les paramètres de maille a et c diminuent lorsque x augmente jusqu’à 0.44. Cette étude illustre les avantages de la microscopie électronique analytique à haute résolution spatiale, utilisée en complément des techniques de caractérisation conventionnelles, pour corréler les caractéristiques structurales et chimiques de matériaux finement divisés.

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Copyright information

© The Clay Minerals Society 1989

Authors and Affiliations

  • F. Thevenot
    • 1
  • R. Szymanski
    • 1
  • P. Chaumette
    • 1
  1. 1.Institut Français du PétroleRueil-Malmaison CedexFrance

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