Marie-Hélène Tuilier

Synthesis and characterization of montmorillonite-type phyllosilicates in a fluoride medium

Abstract The fluorine route is thoroughly investigated for the hydrothermal synthesis of montmorillonite in the Na2O-MgO-Al2O3-SiO2-H2O system. Using the optimal conditions suggested by Reinholdt et al. (2001) for the crystallization of pure montmorillonites with the formula Na2x(Al2(1−x)Mg2x □)Si4O10(OH)2, several parameters (x, Mg content, duration of crystallization, F/Si atomic ratio, pH, nature of counterbalance cation) are varied independently from their ideal values. The products are analysed by various techniques (X-ray diffraction, thermogravimetric analysis-differential thermal analysis, 29Si, 27Al and 19F magic angle spinning-nuclear magnetic resonance). It appears that a pure montmorillonite can only be obtained within a narrow x range (0.10 ≤x ≤ 0.20). The presence of F in the starting hydrogel and the crystallization time also have significant effects on the purity of the final products. It is shown that a small amount of fluorine is needed for the crystallization of pure montmorillonite phyllosilicates.

Nanosized Zinc Sulfide Obtained in the Presence of Cationic Surfactants

O WILEY-VCH Verlag GmbH, D-69469 Weinheim, 1998 0935-9648/98/1208-0946

Fluorine Route Synthesis of Montmorillonites Containing Mg or Zn and Characterization by XRD, Thermal Analysis, MAS NMR, and EXAFS Spectroscopy

17.50+.50/0 Adv. Mater. 1998, 10, No. 12the three-periodic hyperbolic surface can the mean curvature be ev-erywhere identically zero and this is the defining characteristic of aninfinite periodic minimal surface (IPMS, named by Alan Schoen) [7].The cubic bicontinuous phase is a case in point, where three-periodichyperbolic surfaces divide space into two intertwined, continuous,non-intersecting and geometrically identical subvolumes, each resem-bling a 3D network of adjoined tubes. These features distinguish thecubic from the mesh phase, where the curvature of the latter can beconstant but never equal to zero. Inner and outer volumes on eitherside of the mesh surfaces are now distinct, where the exterior volumecomprises two half spaces joined through a lattice of pores while theinterior volume is a 2D tubular network (Fig. 1) [7,8].[10] T. Jiang, G.A. Ozin, J. Mater. Chem. 1997, 7, 2213.[11] I. Sokolov, H. Yang, G.A. Ozin, G. S. Henderson, Adv. Mater. 1997, 9,917.