Crystal-size control and characterization ofNa-4-mica prepared from kaolinite

Tatsuya Kodama; Yoshinao Harada; Masahito Ueda; Ken-ichi Shimizu; Kenji Shuto; Sridhar Komarneni; Wilfried Hoffbauer; Hartmut Schneider

doi:10.1039/B009418H

Tatsuya Kodama,*^a Yoshinao Harada,^a Masahito Ueda,^a Ken-ichi Shimizu,^b Kenji Shuto,^c Sridhar Komarneni,^d Wilfried Hoffbauer^e and Hartmut Schneider^f

Author affiliations

* Corresponding authors

^a Department of Chemistry & Chemical Engineering, Faculty of Engineering, Niigata University, 8050 Ikarashi 2-nocho, Niigata, Japan
E-mail: tkodama@eng.niigata-u.ac.jp

^b Graduate School of Science and Technology, Niigata University, 8050 Ikarashi 2-nocho, Niigata, Japan

^c Department of Geology, Faculty of Science, Niigata University, 8050 Ikarashi 2-nocho, Niigata, Japan

^d Materials Research Laboratory and Department of Agronomy, The Pennsylvania State University, University Park, USA

^e Institute of Inorganic Chemistry, University of Bonn, Bonn, Germany

^f Ceramic Department, Institute of Materials Research, German Aerospace Research Establishment-DLR, Koln, Germany

Abstract

A simple and economical method for the synthesis of high-charge-density Na-4-mica (ideal chemical composition of Na₄Mg₆Al₄Si₄O₂₀F₄·xH₂O) from kaolinite was investigated. Synthesis conditions were varied to control crystal size. This novel swelling Na-4-mica was synthesized from a mixture of kaolinite, magnesium nitrate (or ultrafine MgO) and NaF at 850 °C, and characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), particle size analysis by laser diffraction and ²⁷Al and ²⁹Si magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy. Decreasing the mass of NaF flux during the crystallization of Na-4-mica reduced the crystallite size from 2 to 0.2 µm. As the crystallite size decreased, the average particle size of the mica decreased from 5 to 2 µm. ²⁷Al MAS-NMR spectra showed that all or nearly all Al is in tetrahedral coordination whereas ²⁹Si MAS-NMR spectra showed that the nearest neighbour environment of Si is mainly in Si(3Al), as expected based on the Si∶Al ratio.

Article information

https://doi.org/10.1039/B009418H

Article type

Paper

Submitted

24 Nov 2000

Accepted

02 Feb 2001

First published

06 Mar 2001

Download Citation

J. Mater. Chem., 2001,11, 1222-1227

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